ICND1 100-105

Routes not added to the Routing table

- The ip route command reference an outgoing interface, ans that interface is down. - The ip route command references next-hop router address and there is no route to that next hop address. - There is another route with the same prefix/mask, but with a lower administrative distance.

Cisco Boot Sequence

1) POST (Power ON Self Test) 2) A bootstrap program copied from ROM to RAM 3) The bootstrap program loads the OS 4) The start-up config loaded to RAM

Subnet Masks

A 32-bit number that numerically describes the format of an IP address, by representing the combined network and subnet bits in the address with masks bit values of 1, and representing the host bits in the address with mask bit values of 0.

Ethernet address

A 48-bit (6 byte (binary number, usually written as 12-digit hexadecimal number, used to identify Ethernet nodes in an Ethernet network. Ethernet frames headers list a destination and source address field, used by the Ethernet devices to deliver Ethernet frames to the correct destination.

Port security

A Cisco switch feature in which the switch watches Ethernet frames that come in an interface (port), tracks the source MAC addresses of all such frames, and takes security actions if the number of different such MAC addresses is exceeded.

Secure Shell (SSH)

A TCP/IP layer protocol that supports terminal emulation between a client and server, using dynamic key exchange and encryption to keep the communication private.

Voice VLAN

A VLAN defined for use by IP phones, with the Cisco switches notifying the phone about the voice VLAN ID so that the phone can use 802.1Q frames to support traffic for the phone and the attached PC (which uses a data VLAN).

Data VLAN

A VLAN used by typical data devices connected to an Ethernet , like pc's and servers.

Collapsed core design

A campus LAN design in which the design does not use a separate set of core switches in addition to the distribution switches - in effect collapsing the core into the distribution switches.

Core design

A campus LAN design that connects each access switch to distribution switches, and distribution switches into core switches, to provide a path between all LAN devices.

Multicast IP Address

A class D IPv4 address. when sued as a destination address in a packet, the routers collectively work to deliver copies of the one original packet to all hosts who have previously registered to receive packets sent to that particular multicast address.

Network

A collection of computers, printers, routers, switches, and other devices that can communicate with each other over some transmission medium.

Telco

A common abbreviation for telephone company.

VLAN interface

A configuration concept inside Cisco switches, used as an interface between IOS running on the switch and a VLAN supported inside the switch, so that the switch can assign an IP address and send IP packets into that VLAN.

Wireless LAN Controller

A device that cooperates with wireless lightweight access point (LWAP) to create a wireless LAN by performing some control function for each LWAP and forwarding data between each LWAP and wired LAN.

Stateless Address Autoconfiguration (SLAAC)

A feature of IPv6 in which a host or router can be assigned an IPv6 unicast address without the need for stateful DHCP server.

IOS File System (IFS)

A file system created by a cisco device that uses IOS.

IOS image

A file that contains the IOS.

Routing Update

A generic reference to any routing protocol's message in which it sends routing information to a neighbor.

Ethernet Link

A generic term for any physical link between two Ethernet nodes, no matter what type of cabling is used.

Networking model

A generic term referring to any set of protocols and standard collected into a comprehensive grouping that, when followed by the devices in a network, allows all the devices to communicate. Ex. Include TCP/IP and OSI model.

Protocol Data Unit (PDU)

A generic term referring to the header defined by some layer of a networking model, and the data encapsulated by the header and (possibly trailer) of the layer, but specifically not including any lower-layer headers and trailers.

Dual-Stack Backbones

A hybrid model in which backbone routers have dual-stack functionality, which enables them to route both ipv4 and ipv6 packets. It is an enterprise that uses both IPv4 and IPv6 applications. Running IPv6 and IPv4 together in a network is known as dual-stack routing.

Configuration Register

A in Cisco routers, a 16-bit, user-configuration value that determines how the router functions during initialization. In software, the bit position is set by specifying a hexadecimal value using configuration commands,

Extended Access List

A list of IOS access-list global configuration commands that can match multiple parts of an IP packets, including the source and destination IP address and TCP/UPD ports, for the purpose of deciding which packets to discard and which packets to allow through the router. Extended Access List #: 100 -199 , 2000-2699

Standard Access List

A list of IOS global configuration commands that can match only a packet's source IP address, for the purpose of deciding which packets to discard and which to allow through the router. Standard Access List : 1 - 99, 1300-1999

ARP (Address Resulation Protocol) table

A list of IP addresses of neighbors on the same VLAN, along with their MAC addresses, as kept in memory by hosts and routers.

Routing table

A list of routes in a router, with each route listing the destination subnet and mask, the router interface out which to forward packets destined to the subnet, and as needed, the next-hop routers IP address.

Wire LAN

A local-area network (LAN) that physically transmits bit using cables, often the wire inside cables.

Wireless LAN

A local-area network (LAN) that physically transmits bits using radio waves.

Packet

A logical grouping of bytes that includes the network layer header and encapsulated data, but specifically does not include any headers and trailers below the network layer.

Cisco Discovery Protocol (CDP)

A media - and protocol independent device-discovery protocol that runs on most Cisco-manufactured equipment, including routers, access servers, and switches. Using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN.

Router Advertisement (RA)

A message defined by the IPv6 NDP, used by routers to announce their willingness to act as an IPv6 router on a link. These can be sent in responds to a previously received NDP Router Solicitation (RS) message. This message is sent by the router, lists many facts including the link-local ipv6 address of the router. When unsolicited it is sent to all ipv6 hosts using the local-scope multicast address FF02::1.

Router Solicitation (RS)

A message defined by the IPv6 NDP, used to ask any routers on the link to reply, identifying the router, plus other configuration settings (prefixes and prefix lengths). his message is sent to all ipv6 routers, so it uses the FF02::2 local scope multicast address.

Neighbor Solicitation (NS)

A message defined by the IPv6 NDP, used to ask neighbor to reply with a Neighbor Advertisement, which lists the neighbor's MAC address. The NS message is sent to the solicited-node multicast address associated with the target address, so message is processed only by hosts whose last six digits match the address that is being queried.

Neighbor Advertisement (NA)

A message defined by the IPv6 NDP, used to declare to other neighbors a hos'ts MAC address. This message lists the sender's address as the target address, along with the matching mac address. It is sent back to the unicast address of the host that sent the original NS message.

Log Message

A message generated by any computer, but including Cisco routers and switches, for which the device OS wants to notify the owner or administrator of the device about some event.

SCP (Secure Copy Protocol)

A method to securely copy files that uses the authentication and encryption services of SSH; can be used to copy files to/from Cisco devices.

Dual stack

A mode of operation in which a host or router runs both IPv4 and IPv6.

NTP Client/Server mode

A mode of operation with the network Time Protocol in which the device acts as both an NTP client, synchronizing its time with some servers, and as an NTP server, supplying time information to clients.

User mode

A mode of the user interface to a router or switch in which the user can type only non disruptive EXEC commands, generally just to look at the current status.

100Base-T

A name for the IEEE Fast Ethernet standards that use two pare copper cabling, speed 100 Mpbs and a maximum cable length of 100 maters.

1000Base-T

A name for the IEEE Gigabit Ethernet standard that uses four pair copper cabling, a speed of 1000 Mpbs and max length on 100 m.

Discontiguous Network

A network topology in which a subnet of network X are separated by subnets of some other classful network.

Star topology

A network topology in which endpoints on a network are connected to a common central device by point-to-point links.

Full mesh

A network topology in which more than two devices can physically communicate and, by choice, all pairs of devices are allowed to communicate directly.

Partial mesh

A network topology in which more than two devices could physically communicate but, by choice, only a subset of the pairs of devices connected to the network is allowed to communicate directly.

Contiguous Network

A network topology in which subnets of network X are not separated by subnets of any other classful network.

Ordered data transfer

A networking function, included in TCP, in which the Protocol defines how the sending host should number the data transmitted, defines how the receiving device should attempt to reorder the data if it arrives out of order, and specifies to discard the data if it cannot be delivered in order.

IPv6 over dedicated WAN links

A new development of IPv6 is created. In this model, IPv6 hierarchy, addressing and protocols are used by all nodes. However, this model involves cost for creating IPv6 WAN circuits. This solution is not designed for LAN translation but rather translation over WAN links.

Universal Device Identifier (UDI)

A number that Cisco assigns to each router to uniquely identify the router's type and unique serial number, for the purpose of enabling the IOS software licensing process to work.

Enable mode

A part of Cisco IOS CLI in which the user can use the most powerful and potentially disruptive commands on a router or switch, including the ability to then reach configuration mode and reconfigure the router.

Wide-area Network (WAN)

A part of a larger network that implements mostly OSI layer 1 and 2 technology, connects sites that typically far apart, and uses a business model in which consumers must lease the WAN from a service provider (often a telco).

Configuration mode

A part of the Cisco IOS software CLI in which the user can type configuration commands that are then added to the devices currently used configuration file (running-config)

RJ45

A popular type of cabling connector used for Ethernet cabling.

Traceroute

A program available on many systems that traces that path that a packets takes to a destination. It is used mostly to debug routing problems between hosts. Note that cisco IOS version of of the traceroute command uses UDP for outbound messages, while windows version uses ICMP for outbound messages.

NDP (Neighbor Discovery Protocol)

A protocol that is part of the IPv6 protocol suite, used to discover and exchange information about devices on the same subnet (neighbors). In particular, it replaces the IPv4, ARP protocol.

Spanning Tree Protocol (STP)

A protocol that's uses the spanning Tree algorithm, allowing a switch to dynamically work around loops in a network topology by creating STP. Switches exchange bridge protocol data unit (BPDU) message with other switches to detect loops and then remove the loops by blocking selected switch interfaces.

Network Time Protocol (NTP)

A protocol used to synchronize time-of-day clocks so that multiple devices use the same time of day. which allow log messages to be more easily matched based on their time stamps.

Bandwidth

A reference to the speed of a networking link. Its origins come from earlier communication technology in which the range, or width, of the frequency band dictated how fast communications could occur.

Network Route

A route for a classful network

Host Route

A route with /32 mask, which by virtue of this mask represents a route to a single host IP address.

Interior Gateway Protocol (IGP)

A routing protocol designed for use within a single organization. The three IPv4 IGP routing protocol are (RIPv3, OSPF, and EIGRP).

Auto-summarization

A routing protocol feature in which the route that sits at the boundary between different calssful networks will automatically advertise a route for one entire classful network into the other classful network, and vise versa.

Exterior Gateway protocol (EGP)

A routing protocol that was designed to exchange routing information between different autonomous systems.

Device Hardening

A security term referring to whatever activities one might do to secure a device or type of device, for instance, by securing login access to a router or switch, and using ACL's to limit what user can login to a router or switch.

Leased line

A serial communication circuit between two points, provided by some service provider typically a telephone company (telco).

Ethernet

A series of LAN standards defined by the IEEE.

Syslog Server

A server application that collects syslog messages from many devices over the network, and provides a user interface so that IT administration can view the log messages to troubleshoot problems.

AAA server

A server that hold security information and provided services related to the user login.

Broadcast Domain

A set of all devices that receive broadcast frames originating from any device within the set. Devices in the same VLAN are in the same broadcast domain.

Routing protocol

A set of messages and processes with which routers can exchange information about routes to reach subnets in a particular network.

Collision domain

A set of network interface cards (NIC) for which a frame sent by one NIC could result in a collision with a frame sent by any other NIC in the same domain.

IOS feature Set

A set of related features that can be enabled on a router to enable certain functionality.

Rommon

A shorter name for ROM monitor, which is a low-level operating system that can be loaded into Cisco routers for several seldom-needed maintenance tasks, including password recovery and loading a new IOS when flash memory has been corrupted.

Code integrity

A software security term that refers to how likely that the software (code) being used is the software supplied by the vendor, unchanged, with no viruses or other changes made to the software.

Subnet Broadcast Address

A special address in each IPv4 subnet, specifically the largest numeric address in the subnet, designed so that packets sent to this address should be delivered to all hosts in that subnet.

Subnet Router Anycast Address

A special anycast address in each IPv6 subnet, reserved for use by routers as a way to send a packet to any router on the subnet. The address's value in each subnet is the same number as the subnet ID.

All-nodes Multicast Address

A specific IPv6 multicast address, FF02::1, with link-local scope, used to send packets to all devices on the link that supports IPv6.

All-Routers multicast Address

A specific IPv6 multicast address, FF02::2, with link-local scope, used to send packets to all devices that act as IPv6 routers on the local link. When an IPv6 sends an RS, the destination address will be "all router" multicast of FF02::2.

MD5 hash

A specific mathematical algorithm intended for use in various security protocols. In the context of Cisco routers and switches, the devices store the MD5 hash of certain passwords, rather then the passwords themselves, in an effort to make the device more secure.

Floating Static Route

A static IP route that uses a higher administrative distance than other routes, typically router learned by a routing protocol. As a result, the router will not use static route, if the routing protocol route has been learned, but then use the static route if the routing protocol fails to learn the route.

MAC address table

A table of forwarding information held by a Layer 2 switch, built dynamically by listening to incoming frames and used by the switch to match frames to make decision about where to forward the frame.

Ethernet over MPLS

A term referring specifically to how a service provider can create an Ethernet WAN service using an MPLS network. More generally, a term referring to Ethernet WAN services. EoMPLS is tunneling mechanism that transports layer 2 Ethernet frames over an MPLS network. You can connect two layer 2 networks that are in different locations without requiring bridges, routers, or switches at the locations.

Frame

A term referring to a data link header and trailer, plus the data encapsulated between the header and trailer.

Ethernet Frame

A term referring to an Ethernet data link header and trailer, plus the data encapsulated between the header and trailer.

Prefix mask / CIDR (Class Less Inter-Domain Routing)

A term to describe an IPv4 subnet mask when represented as a slash (/) followed by a decimal number. The decimal number is the number of binary 1s in the mask.

Stateless DHCPv6

A term used in IPv6 to contrast with stateful DHCP. Stateless DHCP servers don't lease IPv6 addresses to clients. Instead, they supply other useful information. such as DNS servers ip addresses, but with no need to track information about the clients (state information).

Stateful DHCPv6

A term used in IPv6 to contrast with stateless DHCP. Stateful DHCP keeps track of which clients have been assigned which IPv6 addresses (state information).

Duplicated Address Detection (DAD)

A term used in IPv6 to refer to how hosts first check whether another host is using a unicast address before the first uses that address.

Input Error

A total of many counters, including rants, giants, no buffer, CRC, frame, overrun, and Ignored Counts.

Protocol Translation

A translation method of allowing an IPv6 host to communicate with the IPv4 host. This is accomplished with the help of NAT - Protocol Translation (NAT-PT) used to configure translation between IPv6 and IPv4 hosts. NAT-PT allows communication between IPv6 hosts and application, and native ipv4 hosts and applications.

Solicited-node Multicast Address

A type of IPv6 multicast address, with link-local scope, used to send packets to all hosts in the subnet that share the same value in the last six hex digits of their unicast IPv6 addresses. Begins with FF02::1:FF00:0/104

Serial interface

A type of interface on a router, used to connect to some type of WAN links, particularly leased lines and Frame Relay access links.

ROM (Read Only Memory)

A type of nonvolatile memory that can be read but not written to by the microprocessor.

NVRAM (Nonvolatile RAM)

A type of random access memory (RAM) that retains its contents when a unit is powered off.

Global Unicast Address

A type of unicast IPv6 address that has been allocated from a range of public globally unique ip addresses, as registered through IANA/ICANN, its member agencies, and other registries of ISP's.

Link-Local Address

A type of unicast address that represents an interface on a single data link. Packets sent tot a link-local address cross only that particular link and are never forwarded to other subnets by a router. Used for communication that do not need to leave the local link.

Flesh Memory

A type pf read/write permanent memory that retains its contents even with no power applied to the memory, and uses no moving parts, making the memory less likely to fail over time.

Metric

A unit measures used by routing protocol algorithms to determine the best route for traffic to use to reach a particular destination.

Local username

A username (with matching password), configured on a router or switch. It is considered local because it exists on the router or switch, and not on a remote server.

Access point

A wireless LAN device that provides a means for wireless client to send data to each other and to the rest of wired network, with the AP connecting to both the wireless LAN and the wired Ethernet LAN.

ARP

Address Resolution Protocol. An internet protocol used to map an IP address to a MAC address. Defined in RFC 826. uses broadcasts to find the mac address associated with a known IP address.

Global Unicast

Addresses that work like public IPv4 addresses. The organization that needs IPv6 addresses asks for registered IPv6 address block, which is assigned as global routing prefix. Global Unicast starts with 2 or 3.

Frame Check Sequence

Afield in many data link trailer used as part of the error detection process.

Layer 3 Switch

Aka multiplayer switch, a LAN switch that can also perform Layer 3 routing functions.

Trunking administrative mode

Also called VLAN trunking. A method using either the Cisco ISL or IEEE 802.1q protocol to support multiple VLANs, allowing traffic from those VLANS to cross a single link.

Named Access List

An ACL that identifies the various statements in the ACL based on a name, rather than a number.

Crossover cable

An Ethernet cable that swaps the pare used for transmission on one device to a pair used for receiving on the device on the opposite end of the cable. this cable, which connects pins 1 and 3, 3 and 6, 3 and 1, and 6 and 2.

Broadcast frame

An Ethernet frame sent to destination address FFFF.FFFF.FFFF, meaning that the frame should be delivered to all hosts on that LAN.

Known unicast frame

An Ethernet frame whose destination MAC address is listed in the switches MAC address table, so the switch will forward the frame out the one port associated with that entry in the MAC address table.

Unknown unicast frame

An Ethernet frame whose destination switches MAC address is not listed in the MAC address table, so the switch must flood the frame.

Autonegotiation

An IEEE standard mechanism (802.3u) with which two nodes can exchange message to use the same Ethernet standards on both ends of the link, ensuring that the link functions and functions well.

Link Layer Discovery Protocol (LLDP)

An IEEE standard protocol (IEEE 802.1AB) that defined messages, encapsulated directly in Ethernet frames so they do not rely on a working IPv4 or IPv6 network, for the purpose of giving devices a means of announcing basic device information to other devices on the LAN. It is a standardized protocol similar to Cisco Discovery Protocol (CDP)

Extended ping

An IOS command in which the ping command accepts many other options besides just the destination IP address.

Configuration Archive

An IOS concept by which some IOS file system is defined as a place to store configuration archives of a Cisco router or switch, allowing automatic and manual archive, and easier restore.

IP network

An IPv4 class A,B,C network; called a class full network because these network are defined by the class rules for IPv4 addressing.

Classful IP network

An IPv4 class A,B,or C network; called a calssful network because these networks are defined by the class rules for IPv4 addressing.

Global Routing Prefix

An IPv6 prefix that defines an IPv6 address block made up of global unicast addresses, assigned to one organization, so that the organization has a block of globally unique IPv6 addresses to use in its network.

Anycast Address

An address shared by two or more hosts that exist is different parts of the network, so that by design, the routers will forward packets to the nearest of the two servers, allowing clients to communicate with the nearest such server, not caring which particular server with which the client communicates.

Overlapping subnets

An incorrect IP subnet design condition in which one subnet's range if addresses includes addresses in the range of another subnet.

Classless Routing Protocol

An inherent characteristic of a routing protocol, specifically that the routing protocol does send subnet masks in its routing updates, thereby removing any need to make assumptions about the addresses in a particular subnet or network, making it able to support VLSM and manual route summarization.

Error Disable

An interface state on LAN switches that can be the result of one of many security violations.

Command-line interface (CLI)

An interface that enables the users to interact with the operating system by entering commands and optional arguments.

Cable Ethernet

An internet access technology that uses a cable TV (CATV) cable, normally used for video, to send and receive data.

Ping

An internet control Message protocol (ICMP) echo message and its reply; ping often is used in ip networks to test reachability of a network device. By default, a ping used on Cisco IOS using the default parameters will send five echo messages, and each will have a timeout of 2 seconds.

Unicast IP address

An up address that represents a single interface. In IPv4, these addresses come from the class A,B,C ranges.

NAT overload

Another term for Port Address Translation (PAT). One of several methods of configuring NAT, in this case translating TCP and UDP flows based on port numbers in addition to using one or only a few inside global addresses.

Public IP network

Any IPv4 class A, B, or C network assigned for use by one organization only, so that the addresses in the network are unique across the internet, allowing packets to be sent through the public Internet using the addresses.

NTP Client

Any device that attempts to use the Network Time Protocol to synchronize its time by adjusting the local device's time based on NTP message received from a server.

NTP Server

Any device that uses Network Time Protocol to help synchronize time-of-day clocks for other devices by telling other devices its current time.

Private IP network

Any of the IPv4 Class A, B, or C networks as defined by RFC 1918, intended for use inside a company but not used as public IP networks. Private IP address range: class A: 10.0.0.0 class B: 172.16.0.0 - 172.31.0.0 class C: 192.168.0.0 -192.168.255.0

AAA

Authentication, Authorization, and Accounting.

CIDR

Classless inter-domain routing. An RFC standard tool for global IP address range assignment. CIDR reduces the size pf internet router's IP routing tables, helping deal with the repaid growth of the Internet. The term classless refer to the fact that the summarized groups of networks represent a group of addresses that do not conform to IPv4 classful grouping rules.

Authentication

Confirms the identity of the user or device.

Collision

Counter of all collision that occur when the interface is transmitting a frame.Does not point to duplex mismatch, collision occurs as normal part of the half-duplex logic imposed by CSMA/CD.

Authorization

Determines what the user or device is allowed to do.

DSL

Digital subscribers line. Public network technology that delivers high bandwidth over conventional telco local-loop copper wiring at limited distances. Typically used as an internet access technology, connecting a user to an ISP.

Classful Routing Protocol

Does not transmit the mask information along with the subnet number, and therfore must consider class A,B,C network boundaries and perform autosummarization at those boundaries. Does not support VLSM.

DNS

Domain Name System. An application layer protocol used throughout the internet for translating host names into their associated IP addresses. associates names with IP addresses.

Product Authorization Key (PAK)

During the IOS licensing process, the number that cisco assigns a customer giving the customer the right to enable an IOS feature set on one of the customer's routers of a particular model series.

DHCP Client

Dynamic Host Configuration Protocol, Any device that uses DHCP protocols to ask to lease an IP address from a DHCP server, or learn any IP settings from that server.

Resident Subnet

Each IP subnet contains a number of unicast IP addresses; that subnet is the resident subnet for each of those addresses; that is, the subnet in which those addresses reside.

CSMA/CD

Ethernet Media Access Control (MAC) method uses a back-ff algorithm to calculate random times , is is used by Ethernet technology to minimize collisions in the network. caused an Ethernet NIC to first listen, making sure the link is quite before sending. This allows many device to share the link and minimize the number of collisions. When collision do occur, the NIC handles the problem by waiting a random amount of time for a quite link and then re-transmit the Ethernet Frame. Networks are segmented into multiple collision using switches for CSMA/CD networks. network normally operates on half-duplex mode Gigabit Ethernet uses CSMA/CD as its media access control method.

IPv6 route forward

For configuring static routes, the forwarding details could be the outgoing interface on a serial point-to-point connection, the global IPv6 address of the next-hop router, or the combination of the link-local address of the next-hop router with the egress (outbound) interface that the local router should use.

Zero Subnet

For every classful IPV4 network that is subnetted, the one subnet whose subnet number has all binary 0's in the subnet part of the number. In decimal, the zero subnet can be easily identified because it is the same number as the classful network number.

Inside Local

For packets sent to and from a host that resides inside the trusted part of a network that uses NAT, a term referring to the IP address used in the headers of those packets when those packets traverse the enterprise (private) part of the network.

Inside Global

For packets sent to and from a host that resides inside the trusted part of a network that uses NAT, a term referring to the IP address used in the headers of those packets when those packets traverse the global (public) Internet.

terminal monitor / terminal no monitor

For user (SSH or Telnet) session, toggles on (terminal monitor) or off (terminal no monitor) the receipt of log messages, for that one session, if logging monitor is also configured.

Terminating a TCP Connection

Four-way sequence: TCP-ACKL, FIN ---> (sent by the terminator) TCP-ACK <---- (sent by the terminated verifying) TCP-ACK, FIN <--- (sent by the terminated, saying its ready to end the connection) TCP-ACK ---> (Final message sent by the terminator indicating the completion of termination)

Rants

Frame that did not meet the minimum frame size requirement (64 bytes); can be caused by collision.

Giants

Frame that exceed the maximum frame size requirement (1518 bytes).

Reverse Route

From one host's perspective, for packets sent back to the host from another host, the route over which the packet travels.

Forward Route

From one host's perspective, the route over which a packet travels from that host to some other host.

Unicast address

Generally, any address in networking that represents a single device or interface, instead of a group of address (as would be represented by a multicast or broadcast address).

Broadcast address

Generally, any address that represents all devices, and can be used to send one message to all devices. The MAC ADDRESS OF ALL 1S OR FFFF.FFFF.FFFF in hex are broadcast address.

Half duplex

Generically, any communication in which only one device at a time can send data. In Ethernet LANs, the normal result of the CSMA/CD algorithm that enforces the rule that only one device should send at any point in time.

Full duplex

Genetically, any communication in which two communicating devices can concurrently send and receive data. In Ethernet LANs, the allowance for both devices to send and receive at the same time, allowed when both devices disable their CSMA/CD login.

HDLC

High-Level Data Link Control. A bit oriented synchronous data link layer 2 protocol developed by international organizations for Standardization (ISO). Default wan Protocol on Cisco routers, Cisco proprietary when used with Cisco routers.

HTTP

Hypertext Transfer Protocol. The protocol used by web browsers and web servers to transfer files, such as text and graphic files.

IANA address range

IANA reserved all Ipv6 addresses that begin with 2 or 3 as global unicast addresses. This address range can be written succinctly as prefix 2000::/3. This means that the first 3 bits must be 001). In hex, the first group of numbers will be in the range of 2000 through 3fff.

10BASE-T

IEEE standard name 802.3, Ethernet speed 10Mbps, UTP copper cable and maximum length 100 m

1000BASE-T

IEEE standard name 802.3ab, Gigabit Ethernet speeds 1000Mbps, UTP Copper cable, maximum length 100m.

10GBASE-T

IEEE standard name 802.3an, 10 Gig Ethernet speeds 10 Gbps, UTP copper cable, maximum length 100 m.

100BASE-T

IEEE standard name 802.3u, Fast Ethernet speeds 100Mbps, UTP copper cable, maximum length 100m.

1000BASE-LX

IEEE standard name 802.3z, Gigabit Ethernet speeds 1000Mbps, fiber cable, maximum length 5000m.

Local Broadcast IP address

IPv4 address 255.255.255.255. A packet sent to this address is sent as a data link broadcast, but only flows to hosts in the subnet which it was originally sent. Routers do not forward these packets.

configuration register hex character

If the boot field's last character of the configuration register is a 0, then the router boots ROMMON. If it is one 1, then the router loads the first valid IOS image on flash. If i is 2 or higher, then it checks the startup-config for any instructions, and is the absence of any, it loads the first valid IOS file in flash (similar to the value being 1)

Running-config file

In Cisco IOS switches and routers the name of the file that resides in RAM memory, holding the device's currently used configuration.

Running-config file

In Cisco IOS switches and routers, the name of the file that resided in RAM memory, holding the device's currently used configuration.

Startup-config file

In Cisco IOS switches and routers, the name of the file that resides in NVRAM memory, holding the device's configuration that will be loaded into RAM as the running-config file when the device is next reloaded or powered on.

Login Banner

In Cisco router or switch, a text message that the router. switch displays fir the user during the login process.

History buffer

In Cisco router or switch, the function by which IOS keeps a list of commands that user has used in this login session.

Administrative Distance

In Cisco routers, it means for one route to choose between multiple routes to reach the same subnet when those routes were learned by different routing protocols. the lower the administrative distance, the better the source of the routing information.

Straight through cable

In Ethernet, a cable that connects the wire on pin 1 on one end of the cable to pin 1 on the other end of the cable, pin 2 on one end to pin 2 on the other end, and so on.

Prefix

In IPv6, this term refers to the number of identifies a group of IPv6 addresses. An IPv6 subnet identifier.

Port

In TCP and UDP, a number that is used to uniquely identify the application process that either sent (source port) or should receive (destination port) data. In LAN switching, another term for switch interface.

Segment

In TCP, the term segment refers to L4PDU, also in TACP the process of accepting a large chunk of data from the application layer and braking it into smaller pieces that fit into TCP segments.

Distribution layer

In a campus LAN design, the switches that connects to access layer switches as the most efficient means to provide connectivity from the access layer into the other parts of the LAN. Distribution layer aggregates the access layer.

Core layer

In a campus design, the switches that connects the distribution layer switches, and to each other, to provide connectivity between various distribution layer switches. Core layer aggregates the distribution layer.

Next-hop Router

In an IP route ina routing table, part of a routing table entry that refers to the next IP router (by IP addresses) that should receive packets that match the route.

Access layer

In campus LAN design, the switches that connect directly to endpoint devices, and also connect into the distribution layer switches.

Trunk

In campus LANs, an Ethernet segment over which the device add a VLAN header that identifies the VLAN in which the frame exists.

Subnet Number / ID / Address

In ipv4 a dotted-decimal number that represents all addresses in a single subnet. Numerically, the smallest value in the range of numbers in a subnet, reserved so that it cannot be used as the unicast ip address by a host.

DNS Reply

In the Domain Name System, a message sent by a DNS server to a DNS client in response to a DNS Request, identifying the IP address assigned to a particular host-name or fully qualified domain name (FQDN).

DNS Request

In the Domain Name System, a message sent to a DNS client to a DNS server, listing a host-name or fully qualified domain name (FQDN), asking the server to discover and reply with ip address associated with that host-name or FQDN.

IEEE

Institute of Electrical and Electronics Engineers. A professional organization that develops communications and networks standards, among other activates.

Same-layer

Interaction when a particular layer on one computer wants to communicate with the same layer of another computer, the two computer uses headers to hold the information that they want to communicate.

UP and UP status

Jargon referring to the two interface states on a Cisco IOS router or switch (line status and protocol status), with the first "up" referring to the line status and the second "up" referring to the protocol status. An interface in this state should be able to pass data link frames.

Layer 1 problem indicators

Late Collision and collision due to mismatched duplex setting. Late collision can be due to physical cable being longer than standard permits.

Hub

Layer 1 LAN device that provides a centralized connection point for LAN cabling, repeating any received electrical single out all other ports, thereby creating a logical bus.

EUI-64

Literally, s standard for an extended unique identifier that is 64 bit long. Specifically for IPv6, a set of rules for forming the a 64-bit indenfier, sued as the interface ID in IPv6 addresses, by staring with a 48-bit MAC address, inserting FFFF (hex) in the middle, and inverting the seventh bit.

NAT

Network Address Translation , a mechanism for reducing the need for globally unique IP addresses. NAT allows an organization with addresses that are not globally unique to connect to the internet, by translating those addresses into public addresses in the globally routable address space.

Late Collision

Often points to duplex mismatch, late collision that happen after the 64th bytes of the frame has been transmitted. In a properly working Ethernet LAN, collision should occur within the 64th bytes.

De-encapsulation

On a computer that receives data over network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU.

Connected Route

On a router, an IP route added to the routing table when the router interface is both UP and has an IP address configured. The route is for the subnet that can be calculated based on the configured IP address and mask.

Default Route

On a router, the route that is considered to match all packets that are not otherwise matched by some more specific route.

Duplex mismatch

On opposite ends of any Ethernet link, the condition in which one of the two devices uses full-duplex login and the other uses half-duplex logic, resulting in unnecessary frame discards and re-transmission on the link.

ICMP echo request

One type of ICMP message, created specifically to be used as the message sent by the ping command to test connectivity in a network. The ping command sends these message to other hosts, expecting the other host to reply with an ICMP echo reply message.

ICMP echo reply

One type of ICMP message, created specifically to be used as the message sent by the ping command to test the connectivity in a network. the ping command expects to receive these messages from other hosts, after the ping command first sends an ICMP request to the host.

PAT

Port Address Translation, A NAT features in which one inside global IP address supports over 65,000 concurrent TCP and UDP connections.

Configuring Overlapping VLSM Subnets

Preventing the overlap on single router: IOS detects the overlap when the ip address command implies an overlap with another ip address command on the same router. Allowing the overlap on different routers: IOS cannot detect an overlap when an ip address commands overlap with an ip address on another router.

CRC (Cyclic Redundancy Check)

Received frames that did not pass FCS math; can be caused by collisions.

Frame (Interface Counters)

Received frames that have illegal formats, for ex. ending with partial byte, can be caused by collisions.

Accounting

Records information about access attempts, including inappropriate request.

DHCP Server

Software that waits for DHCP clients to request to lease IP addresses, with the server assigning a lease of an IP address as well as listing other important IP setting for the client.

Web server

Software, running on a computer, that stores web pages and sends those web pages to web client (web browsers) that request the web page.

Local Unicast Address

Starts with hex FD, works somewhat like private IPv6 address, with the possibility that multiple organization use the exact same addresses, and with no requirement for registering with any numbering authority.

IP subnet

Subdivision of a class A,B,C network, as configured by a network administrator.

VTP transparent mode

Switches in transparent mode can configure VLANs, but they do not tell other Switches about changes, and they do not learn about VLAN changes from other switches.

Cut-through Switching Method

Switching process does not require a switch to verify the FCS in a frame before forwarding it to the destination port. This type of internal switching method is faster than the store and forward process, but may forward error frames.

10Base-T

The 10-Mbps basedband Ethernet specification using two pairs of twisted-pair cabling (Cat 3,4, or 5): one pare transmits data and the other pare receives data. 10Base-T, which is part of IEEE 802.3 specification, has a distance limit of approximately 100m per segment.

Universal Image

The Cisco IOS universal image contains all feature set for the specific device for which it was made. The administrator just needs to license and enable the specific features he or she desires.

802.11b

The IEEE standard for wireless LANs using the ISM spectrum, DSSS encoding, and speeds of up to 11 Mbps.

802.11a

The IEEE standard for wireless LANs using the U-NII spectrum, OFDM encoding, and speeds of up to 54 Mbps

802.1Q

The IEEE standard protocol for VLAN trunking. Includes concept of native VLAN, for which no VLAN header added, and 4-byte of VLAN header is inserted after the original frames Type/Length field.

802.11n

The IEEE standards for wireless LANs using ISM spectrum, OFDM encoding, and multiple antennas for single-stream speeds up to 150 Mbps.

802.11g

The IEEE standards for wireless LANs using the ISM spectrum, OFDM or DSSS encoding, and speeds of up to 54 Mbps.

Default router (default gateway)

The IP address of some router to which the host sends packets when the packets destination address is on a subnet other than the local subnet.

IPv6 Neighbor Table

The IPv6 equivalent of the ARP table. A table that lists IPv6 addresses of other hosts on the same link, along with their matching MAC addresses, as typically learned using NDP.

Hostname

The alphanumeric name of an IP host.

Variable-length subnet masks (VLSM

The capability to specify a different subnet mask for the same Class A, B, or C netowrk number on different subnets. VLSM can help optimize available address space.

Trunking operational mode

The current behavior of a Cisco switch interface for VLAN trunking.

Distance Vector

The logic behind the behavior of some interior routing protocols, such as RIP. Distance vector routing algorithms call for each router to send its entire routing table in each update, but only to its neighbors. Distance vector algorithms can be prone to routing loops nut are computationally simpler than link-state routing algorithms.

Boot Field

The low-order 4 bits of the configuration register in a Cisco router. The value in the boot field in part tells the router where to look for a Cisco IOS image to load.

Wildcard Mask

The mask used in Cisco IOS ACL commands and OSPF and EIGRP network commands.

Hop count

The metric used by the RIP routing protocol. Each router in an IP route is considered a hop.

Transparent Bridges

The name of a networking device that was a precursor to modern LAN switches. Bridges forward frames between LAN segment based on the destination MAC address.

DHCP Relay Agent

The name of the Router IOS feature that forwards DHCP message from client to servers by Changing the destination IP address from 255.255.255.255 to the IP address of the DHCP server.

Internetwork Operating System (IOS)

The operating system (OS) of Cisco routers and switches, which provided the majority of router's or switch's features, with the hardware providing the remaining features.

Connection Establishment

The process by which connection oriented protocol creates a connection. With TCP, a connection is established by a three-way transmission of TCP segments.

Error detection

The process of discovering weather a data link level frame was changed during transmission. Their process typically uses a Frames Check Sequenc (FCS) field in the data link trailer.

Error recovery

The process of noticing when some transmitted data was not successfully received and resending the data until it is successfully received.

Flow control

The process of regulating the amount of data sent by a sending computer toward a receiving computer. Server always flow control mechanism exist, including TCP flow control, which uses windowing.

Subnetting

The process of subdividing a Class A,B,C network into smaller groups called subnets.

NTP Sychronization

The process with the Network Time Protocol by which different devices send messages, exchanging the devices current time-of-day clock information and other data, so that some devices adjust their clocks to the point that the time-of-day clocks list the same time (often accurate to at least the same second).

Clock rate

The speed at which a serial link encodes bits on the transmission medium.

Telnet

The standard terminal-emulation application layer protocol in the TCP/IP protocol stack . Defined by RFC 854, used for remote terminal connections.

Packet Output

The total number of packets (frames) forwarded out the interface.

EIGRP v6

The version of the EIGRP routing portocol that supports IPv6, and not IPv4.

OSPFv3

The version of the OSPF routing protocol that originally supported only IPv6, and not IPv4, but now supports IPv4 through the use of address family configuration.

Output Errors

Total number of packets (frames) that the switch port tried to transmit, but for which some problem occurred.

URI

Uniform Resource Identifier. The formal and correct term for the formatted text used to refer to objects in an IP network. This text commonly called a URL or web address.

VTP

VLAN Trunking Protocol. A Cisco proprietary messaging protocol used between Cisco switches to communicate configuration information about existence of VLANs, including the VLAN ID and VLAN name.

IP Forwarding

When a destination ip address matches more than one route in a router's IPv4 routing table, the router uses the most specific route-in other words it used the route with the longest prefix. For ex. route with /16 is better than route with /10 or router with /25 is better than route with /20 prefix; and so on.

Outside Global

With source NAT, the one address used by the host that resides outside the enterprise, which NAT does not change, so there is not for a contrasting term.

Unique Local address

Works somewhat like private IPv4 addresses, with the possibility that multiple organization use the exact same addresses, and with no requirement for registering with any numbering authority. A type of IPv6 unicast address meant as replacement for IPv4 private addresses.

IPv6

a 128-bit address assigned to hosts using TCP/IP. Addresses use different formats, commonly using a routing prefix, subnet, and interface ID.

MAC Address

aka hardware address, mac layer address, and physical address, its 48bit (6 byte) long address. The first 6 hex character (24bit) of a MAC address are assigned to the equipment manufacturer, and the second six hex character are assigned by the vendor.

Exec banner

appears after the user login and typically includes information for the connecting users that should not be seen by unauthorized individuals.

Ethernet Frame Type Field

defined the type of protocol listed inside the frame. The type field also indicates the type of layer 3 packets encapsulated within HDLC layer 2 Frame.

Auto-negotiation Fail rule

if auto-negotiation fails: 1) speed: use the slowest supported speed 2) Duplex: if speed is 10 or 100 use half duplex; otherwise use full duplex.

clock rate

interface command that sets the speed at which the router supplies a clocking single, applicable only when the router has a DCE cable installed. The units are bits/second.

IPv6 over tunnels

ipv6 traffic is encapsulated into ipv4 packets. Then these packets are transferred over an IPv4 WAN. This model eliminated the need to create separate circuits to connect to the IPv6 networks. This model increases protocol overhead because of the IPv6 headers and requires one end to be capable of both headers.

Routing

is layer 3 function that refers to the destination of the path from the source to the destination in a network. The following statements are also true of routing: the basic routing function is the determination of the best routing path in an inter-network. routing can use routing protocols to determine the best path to the destination with the help of routing metrics.

Login banner

is shown before the users log in and often used to show warning message to potential hackers.

console port

is used to locally connect and configure a device.

solicited-node multicast address

is used to send traffic to a limited subnet of local devices. One common user is the IPv6 neighbor discovery (ND) process. The RFC specifies that the first 104 bits of the address are always FF02:0000:0000:0000:0000:0001:FF, with the last 24 bits coming from a device's IPv6 address. This means that a device configured with the 2000:B71A:8560:AB73:816A:BE81:AB71:FF01 IPv6 address would have a solicited-node multicast address of FF02::1:FF71:FF01.

service password-encryption

it uses the vigenere cipher algorithm, which is simple in nature.

Fragment-free switching process

only waits to receive the first 64 bytes of the frame before forwarding it to its destination port. Fragment-free internal switching assumes that if there is not error in the first 63 bytes of the data, the frame is error free.

Autonomous Access Point

processes the wireless frames, converts them to a wired frame type, and hands them to the next connecting device.

Ethernet Frame Length Field

specifying the length of the data field, and used in the older specifications of Ethernet.

Store and Forward Switching Method

switching process requires a switch to wait until frame is received before forwarding it to the destination port. Increase latency and runs Frame Check Sequence (FCS) before forwarding it to destination port. However, it ensures error-free frame forwarding because it filters all fame error.

Gigabit Ethernet

the common name for all the IEEE standards that send data at 1 gbps.

Fast Ethernet

the common name for all the IEEE standards that send data at 100 mbps.

Recognizing when VLSM is used

the design must use more than one mask for subnets of a single classful network to using VLSM.

Flag field (Ethernet header)

the flag field is similar to an Ethernet preamble. which is a specific bit pattern that allows a receiving device to realize that a new frame is arriving.

IPv6 DHCP

the four principal messages are Solicit, Advertise, Request, and Reply.

Adjacent-layer interaction

the general topic of how on one computer, two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.

Encapsulation

the placement of data from a higher-layer protocol behind the header (and in some cases, between a header and trailer) of the next-lower-layer protocol.

VoIP

the protocols used in the transmitting VoIP traffic are UDP, RTP (Real Time Protocol:operates at the session layer, layer 5) and Internal Protocol (IP, operates at then network layer, layer 3).

MOTD banner

typically includes a temporary message that often changes

Auxiliary port

typically used to connect an external modem for remote access; this modem can also be used as backup mechanism should the primary data interface fail.

port-security shutdown mode

will disable a port if a device with an unauthorized MAC address attempts to send traffic.

port-security protect mode

will ignore any traffic from unauthorized MAC address, but it not log the violation or send a message to the SNMP manager or disable the port.

port-security restrict mode

will ignore any traffic from unauthorized MAC address, log the violation, and send a message to the SNMP manager (if it is configured), but will not disable the port.

Passive interface

with a routing protocol, a router interface for which the routing protocol in enabled on the interface, but for which the routing protocol does not send routing protocol message about that interface.