Chapter 1 Cisco version 6

1.1.1.5 Primary functions of a router are to:

1. Determine the best path to send packets 2. Forward packets toward their destination

1.1.4.4 terminal history size

200 sets the history buffer size to 200 lines

1.1.3.2 Note:

Accidentally using the clock rate command on a DTE interface generates a "%Error: This command applies only to DCE interface" informational message.

1.3.1.2 Directly connected interfaces -

Added to the routing table when an interface is configured and active.

1.3.1.2 Static routes -

Added when a route is manually configured and the exit interface is active.

1.3.1.2 Local Route interfaces -

Added when an interface is configured and active. This entry is only displayed in IOS 15 or newer for IPv4 routes and all IOS releases for IPv6 routes.

1.3.1.2 Dynamic routing protocol -

Added when routing protocols that dynamically learn about the network, such as EIGRP or OSPF, are implemented and networks are identified.

1.1.3.3 Note:

An interface can generate its own IPv6 link-local address without having a global unicast address by using the ipv6 enable interface configuration command.

1.1.3.3 Unlike IPv4, IPv6 interfaces will typically have more than one IPv6 address.

At a minimum, an IPv6 device must have an IPv6 link-local address but will most likely also have an IPv6 global unicast address. IPv6 also supports the ability for an interface to have multiple IPv6 global unicast addresses from the same subnet.

1.1.1.1 Availability

Availability is the likelihood that the network is available for use when it is required.

1.2.2.2 Enhanced Interior Gateway Routing Protocol (EIGRP) -

Bandwidth, delay, load, reliability. Only EIGRP supports unequal cost load balancing.

1.1.1.3 Components of a Network Capable Device

CPU, OS, Memory and storage (RAM, ROM, NVRAM, Flash, hard drive)

1.2.2.2 Open Shortest Path First (OSPF) -

Cisco's cost based on cumulative bandwidth from source to destination

1.1.1.6 Fast switching:

Common. When a packet arrives on an interface, it is forwarded to the control plane where the CPU searches for a match in the fast switching cache. If it is not there, it is process switched and forwarded to the exit interface. The flow of information for the packet is also stored in the fast switching cache. If another packet going to the same destination arrives on an interface, the next hop information in the cache is reused without CPU intervention.

1.1.3.3 An IPv6 interface must be:

Configured with IPv6 address and subnet mask - Use the ipv6 address ipv6-address/prefix-length [link-local | eui-64] interface configuration command. Activated - The interface must be activated using the no shutdown command.

1.1.3.2 To be available, an interface must be:

Configured with an IP address and a subnet mask - Use the ip address ip-address subnet-mask interface configuration command. Activated - By default, LAN and WAN interfaces are not activated (shutdown). To enable an interface, it must be activated using the no shutdown command. (This is similar to powering on the interface.) The interface must also be connected to another device (a hub, a switch, or another router) for the physical layer to be active.

1.0 What does a router do?

Connects one network to another network.

1.1.2.6 Console access requires:

Console cable - RJ-45-to-DB-9 serial cable or a USB serial cable Terminal emulation software - Tera Term, PuTTY, HyperTerminal

1.1.1.1 Cost

Cost indicates the general expense for purchasing of network components and installation and maintenance of the network.

1.1.1.7 ROM stores:

Diagnostics and boot instructions

1.1.4.1 show ip interface brief

Displays a summary for all interfaces including the IPv4 address of the interface and current operational status.

1.1.4.1 show interfaces -

Displays interface information and packet flow count for all interfaces on the device.

1.1.4.1 show ip interface -

Displays the IPv4 related information for all interfaces on a router.

1.1.4.1 show running-config interface interface-id -

Displays the commands configured on the specified interface.

1.1.4.1 show ip route -

Displays the contents of the IPv4 routing table stored in RAM. In Cisco IOS 15, active interfaces should appear in the routing table with two related entries identified by the code 'C' (Connected) or 'L' (Local). In previous IOS versions, only a single entry with the code 'C' will appear.

1.0 What devices function at the data link layer, Layer 2, and are used to forward Ethernet frames between devices within the same network?

Ethernet switches.

1.1.1.5 What are the different data link technologies that a router can connect to?

Ethernet, PPP, Frame Relay, DSL, cable, and wireless (802.11, Bluetooth, etc.)

1.1.3.2 Depending on the type of interface, additional parameters may be required.

For example, in the lab environment, the serial interface connecting to the serial cable end labeled DCE must be configured with the clock rate command.

1.2.2.2 Routing Information Protocol (RIP) -

Hop count

1.1.1.7 Flash stores:

IOS and system files

1.3.1.2 C -

Identifies a directly connected network.

1.3.1.2 D -

Identifies a dynamically learned network from another router using EIGRP.

1.3.1.2 O -

Identifies a dynamically learned network from another router using the OSPF routing protocol.

1.3.1.2 S -

Identifies a static route created to reach a specific network.

1.1.2.2 IP address

Identifies a unique host on a local network.

1.3.1.3 Route timestamp -

Identifies how much time has passed since the route was learned.

1.3.1.3 Route source - Outgoing interface - Identifies the exit interface to use to forward a packet toward the final destination.

Identifies how the route was learned.

1.1.2.2 Default gateway

Identifies the IP address of the router to send a packet to when the destination is not on the same local network subnet.

1.3.1.3 Next-hop -

Identifies the IPv4 address of the next router to forward the packet to.

1.3.1.2 L -

Identifies the address assigned to a router's interface. This allows the router to efficiently determine when it receives a packet for the interface instead of being forwarded.

1.3.1.3 Destination network -

Identifies the address of the remote network.

1.3.1.3 Outgoing interface -

Identifies the exit interface to use to forward a packet toward the final destination.

1.3.1.3 Administrative distance -

Identifies the trustworthiness of the route source. Lower values indicate preferred route source.

1.3.1.3 Metric -

Identifies the value assigned to reach the remote network. Lower values indicate preferred routes.

1.1.2.2 Subnet mask

Identifies with which network subnet the host can communicate.

1.2.2.1 Directly connected network -

If the destination IP address of the packet belongs to a device on a network that is directly connected to one of the interfaces of the router, that packet is forwarded directly to the destination device. This means that the destination IP address of the packet is a host address on the same network as the interface of the router.

1.2.2.1 Remote network -

If the destination IP address of the packet belongs to a remote network, then the packet is forwarded to another router. Remote networks can only be reached by forwarding packets to another router.

1.2.2.1 No route determined -

If the destination IP address of the packet does not belong to either a connected or remote network, the router determines if there is a Gateway of Last Resort available. A Gateway of Last Resort is set when a default route is configured or learned on a router. If there is a default route, the packet is forwarded to the Gateway of Last Resort. If the router does not have a default route, then the packet is discarded.

1.1.2.7 A switch does not have a dedicated interface to which an IP address can be assigned.

Instead, the IP address information is configured on a virtual interface called a switched virtual interface (SVI).

1.1.3.2 Optionally, the interface could also be configured with a short description of up to 240 characters.

It is good practice to configure a description on each interface. On production networks, the benefits of interface descriptions are quickly realized as they are helpful in troubleshooting and to identify a third party connection and contact information.

1.1.1.5 What does a router use to determine the best path to use to forward a packet?

Its routing table.

1.1.1.6 Cisco Express Forwarding:

Like fast switching, CEF builds a Forwarding Information Base (FIB), and an adjacency table. However, the table entries are not packet-triggered like fast switching but change-triggered such as when something changes in the network topology. Therefore, when a network has converged, the FIB and adjacency tables contain all the information a router would have to consider when forwarding a packet. The FIB contains pre-computed reverse lookups, next hop information for routes including the interface and Layer 2 information. Cisco Express Forwarding is the fastest forwarding mechanism and the preferred choice on Cisco routers.

1.1.3.1 The following configuration tasks should always be performed on a router:

Name the device - (Figure 1) Distinguishes it from other routers. Secure management access - (Figure 2) Secures privileged EXEC, user EXEC, and remote access. Configure a banner - (Figure 3) Provides legal notification of unauthorized access.

1.1.1.6 Process switching:

Older. When a packet arrives on an interface, it is forwarded to the control plane where the CPU matches the destination address with an entry in its routing table, and then determines the exit interface and forwards the packet. The router does this for every packet, even if the destination if the same for a stream of packets. The process switching mechanism is very slow and rarely implemented in modern networks.

1.1.1.1 What are the two types of Network Topology and what do they do?

Physical and logical. Physical topology is how the arrangement of cables, network devices, and end systems. Logical topology is the path over which the data is transferred in a network. It describes how the network devices appear connected to network users.

1.1.1.6 Routers support three packet-forwarding mechanisms:

Process switching, fast switching, and Cisco Express Forwarding (CEF)

1.1.1.1 Reliability

Reliability indicates the dependability of the components that make up the networks, such as the routers, switches, PCs, and servers. Reliability is often measured as a probability of failure or as the mean time between failures (MTBF).

1.1.3.4 Additionally, the IPv4 address assigned to the loopback interface can be significant to processes on the router that use an interface IPv4 address for identification purposes, such as the Open Shortest Path First (OSPF) routing process. By enabling a loopback interface, the router will use the always available loopback interface address for identification, rather than an IP address assigned to a physical port that may go down. Enabling and assigning a loopback address is simple:

Router(config)# interface loopback number Router(config-if)# ip address ip-address subnet-mask Router(config-if)# exit Multiple loopback interfaces can be enabled on a router. The IPv4 address for each loopback interface must be unique and unused by any other interface.

1.3.3.1 A default static route is similar to a default gateway on a host. The default static route specifies the exit point to use when the routing table does not contain a path for the destination network. A default static route is useful when a router has only one exit point to another router, such as when the router connects to a central router or service provider. To configure an IPv4 default static route, use the following command:

Router(config)# ip route 0.0.0.0 0.0.0.0 { exit-intf | next-hop-ip

1.3.3.1 IPv4 static routes are configured using the following command:

Router(config)# ip route network mask { next-hop-ip | exit-intf }

1.1.1.7 RAM stores:

Running configuration

1.1.1.1 Scalability

Scalability indicates how easily the network can accomodate more users and data transmission requirements.

1.1.1.1 Security

Security indicates how protected the network is, including the information that is transmitted over the network.

1.1.1.1 Speed

Speed is the measure of the data rate in bits per second of a given link in the network.

1.1.1.7 NVRAM stores:

Startup configuration

1.1.2.4 A host can be assigned IP address information either:

Statically - The host is manually assigned the correct IP address, subnet mask, and default gateway. The DNS server IP address can also be configured. Dynamically - IP address information is provided by a server using the Dynamic Host Configuration Protocol (DHCP). The DHCP server provides a valid IP address, subnet mask, and default gateway for end devices. Other information may be provided by the server.

1.3.3.3 The example in Figure 3 shows the configuration of two static routes from R2 to reach the two LANs on R1. The route to the 2001:0DB8:ACAD:2::/64 LAN is configured with an exit interface, while the route to the 2001:0DB8:ACAD:1::/64 LAN is configured with the next hop IPv6 address.

The next hop IPv6 address can be either an IPv6 global unicast or link-local address.

1.1.1.1 What are they characteristics of a Network?

Topology, Speed, Cost, Security, Availability, Scalability, and Reliability.

1.3.1.1 A routing table is

a data file in RAM that is used to store route information about directly connected and remote networks. The routing table contains network or next hop associations. These associations tell a router that a particular destination can be optimally reached by sending the packet to a specific router that represents the next hop on the way to the final destination. The next hop association can also be the outgoing or exit interface to the next destination.

1.1.2.2 Gateway of last resort

default gateway

1.1.4.2 The show ipv6 interface brief command

in Figure 1 displays a summary for each of the interfaces. The "up/up" output on the same line as the interface name indicates the Layer 1/Layer 2 interface state. This is the same as the Status and Protocol columns in the equivalent IPv4 command. The output displays two configured IPv6 addresses per interface. One address is the IPv6 global unicast address that was manually entered. The other address, which begins with FE80, is the link-local unicast address for the interface. A link-local address is automatically added to an interface whenever a global unicast address is assigned. An IPv6 network interface is required to have a link-local address, but not necessarily a global unicast address.

1.1.3.3 The following commands can be used to statically create a global unicast or link-local IPv6 address:

ipv6 address ipv6-address/prefix-length - Creates a global unicast IPv6 address as specified. ipv6 address ipv6-address/prefix-length eui-64 - Configures a global unicast IPv6 address with an interface identifier (ID) in the low-order 64 bits of the IPv6 address using the EUI-64 process. ipv6 address ipv6-address/prefix-length link-local - Configures a static link-local address on the interface that is used instead of the link-local address that is automatically configured when the global unicast IPv6 address is assigned to the interface or enabled using the ipv6 enable interface command. Recall, the ipv6 enable interface command is used to automatically create an IPv6 link-local address whether or not an IPv6 global unicast address has been assigned.

1.1.3.4 The loopback interface

is a logical interface internal to the router. It is not assigned to a physical port and can therefore never be connected to any other device. It is considered a software interface that is automatically placed in an "up" state, as long as the router is functioning.

1.1.3.4 The loopback interface

is useful in testing and managing a Cisco IOS device because it ensures that at least one interface will always be available. For example, it can be used for testing purposes, such as testing internal routing processes, by emulating networks behind the router.

1.2.2.4 Administrative distance

represents the trustworthiness of a route, the lower the number the more reliable the route.

1.1.4.2=3 show ip interface brief |

section, include, exclude, begin

1.1.4.4 show history

shows previous commands that were entered

1.3.3.3 Static IPv6 routes are configured using

the ipv6 route ipv6-prefix/prefix-length {ipv6-address|interface-type interface-number} global configuration command.

1.3.3.3 To configure a default static IPv6 route,

use the ipv6 route ::/0 {ipv6-address | interface-type interface-number} global configuration command.

1.3.4.4 To enable IPv6 routers to forward traffic,

you must configure the ipv6 unicast-routing global configuration command.