Network +: Routing
Network Address Translation (NAT) Such as Source NAT; Destination NAT; Static NAT; and Dynamic NAT
To solve the security (hackers from knowing your exact IP), not enough IPs for ISPs to lease out, and the high cost of IP usage, NAT addresses the 3 issues. NAT replaces the source (sender) IP of a sending computer with the source IP from the router on outgoing packets. NAT is performed in a NAT-capable routers.
Dynamic NAT or Pooled NAT
Translates from a pool of global addresses to local addresses. Many to many. For example, the DNAT has 10 routable IPs to serve 40 computers on the LAN.
Frame Relay - long distance connection for networking
Used between LANs overs WAN. Each end user receives a private line to a Frame Relay node. With rural areas where no DSL and cable modem, Frame Relay with a 64 kbps line can be used to connect rural stores to corporation store Includes IP packets
Cisco console cable
Used to configure a Cisco router. One end is a J45 and the other 9-pin female serial connector. Is called rollover or Yost cable Two programs used to connect to a router or switch: 1) PuTTY, 2) HyperTerminal Basic settings: 9600 baud, 8 data bits, 1 stop bit, and no parity.
Asynchronous Transfer Mode (ATM) - long distance connection for networking
Was developed to meet the need of the broadband Integrated Services Digital Network for telecommunication networks.
Enhanced Interior Gateway Routing Protocol (EIGRP)
A Cisco proprietary protocol. It is neither distance vector nor link state protocol, but has the features of both distance vector and link state. Thus it is a hybrid category of protocol. Addressed the limitations of IGRP and added capabilities such as classless support
SecureNAT - from Microsoft Overloaded NAT
A driver extension tonmultiple computers to use a single routable IP with Windows server.
Open Shortest Path First (OSPF)
A link-state routing protocol used in IP networks and falling into the group of interior gateway protocols. It supports classless inter-domain routing.
Static NAT
A one to one mapping of an internal host to a public IP address.
Gateway router
A router that connects with ISP and your local network(s) and LANs. All computers on a network go through a default gateway (gateway router).
Overloaded NAT from Mcrosoft
A single public IP is shared with number of computers shared a network ID. How it works The outgoing IP packet enters the router. The sending IP is replaced with the router's public IP. Next the destination IP and the source ephemeral port to the special database called NAT translation table.
Interior gateway protocol (IGP)
A type of protocol used for exchanging routing information between gateways (routers) within an autonomous system (AS). It is divided into 2 categories: 1) distance-vector Routing protocols and 2) link-state Routing protocols. See the next definitions below for details. Examples of IGP: Open Shortest Path First (OSPF), Routing Info Ptotocol (RIP), Intermediate System to Intermediate System (IS-IS), and Enhanced Interior Gateway Routing Protocol (EIGRP).
Stateful NAT or Stateful Failover NAT from Cisco
Enables multiple routers to do NAT redundantly so that if one goes down, another picks up the traffic.
Enhanced Interior Gateway Routing Protocol (EIGRP)
Is an advanced distance-vector routing protocol for automating decisions and configuration. It is proprietary Cisco protocol for its routers, but published in 2016. It is used on a router to share routes with other routers within the same Autonomous System. It sends only incremental updates, reducing the workload on the router and the amount of data needed to be transmitted. It replaced IGRP in 1993 due to the change to classless IPv4 addresses in the IP, that IGRP could not support
Data Over Cable Service Interface Specification (DOCSIS) - long distance connection for networking
Is an international telecommunications standard permitting the addition of high-bandwidth data transfer to an existing cable TV (CATV) System. Includes IP packets
Terminal emulators (TEs) and console
TEs are programs use to connect to routers and switches. Console is the screen you type on.
Traceroute
a utility application that monitors the network path of packet data sent to a remote computer. Tracert is the command in Windows
TCP/IP ports
-16 bit ports ranging from 0 to 65,535 that is assigned to a particular TCP/IP session -each packet has two ports assigned: destination and ephemeral ports. Destination port is a fixed, predetermined number that defines the function or session type. Common TCP/IP session types use destination port numbers ranging from 0 to 1023. Ephemeral port is an arbitrary number generated by the sending computer. Then the receiving computer uses the ephemeral port as a destination address so that the sending computer knows which application to use for the returning packet. The ephemeral ports range from 1024 to 5,000.
Types of OSPF Routers
1) Internal Router (IR) - it has all interfaces belonging to the same area. 2) Area Border Router (ABR) - it connects one or more areas to the main backbone network. Thus, ABR is a member of all areas it is connected to. It keeps multiple copies of the link-state database in memory, one for each area to which that router is connected. 3) backbone router (BR) - it has an interface to the backbone area. It can be an area router too, but does not have to be. 4) Autonomous System Boundary Router (ASBR) - it connects with other routers using more than one routing protocol and exchanges routing info with routers' autonomous systems. It runs an exterior routing protocol (BGP - border gateway protocol - a standardized exterior gateway protocol used to exchange routing and reachability info among autonomous systems (AS) on the internet. The network admin decides on its routing paths, network policies, rules) or use static routes or both.
Distance-vector Routing protocol
Determines the best route for data packets based on distance. It measures a number of routers a packet has to pass, called one hop for each router. Comparing to link-state protocols required a router to inform all the nodes in a network of topology changes, distance-vector routing protocols have less computational complexity and message overhead. An example is Routing Info Protocol.
Autonomous Systems (AS)
Do not use IP (IGP does) addresses, but rather use a special, globally unique Autonomous System Number (ASN) assigned by the Internet Assigned Numbers Authority (IANA). The current ASNs are 32 bits and separated by a dot. AS uses Exterior Gateway Protocol to communicate with each other. The network or networks within an AS communicate among each other with Interior Gateway Protocol. On a Cisco router: Router1(Configuration)# router bgp? <1-65535> Autonomous system number Router1(Config)#router bgp 1902
Routing Info Protocol (RIP)
It is one of the distance vector routing protocols. It limits to 15 hops max in a path from source to destination. Because of the limitation, RIP limits the number of networks it can support. There are 3 versions (RIPv1, RIPv2, and RIPng (for IPv6). RIPv1 is obsolete because it uses class full routing (a network addressing used from 1983 to 1993, when the introduction of classless inter-domain routing (CIDR) emerged). It uses broadcast. MD5 authentication is used for RIP established in 1997. RIPv2 was developed in 1993 and standardized in 1998. It includes the ability to carry subnet information and supports CIDR. The hops are still 15 max. It multicasts the entire routing table to adjacent routers thru address 224.0.0.9. It uses internet standard STD56 for authentication. RIP next generation (RIPng) is an extension of RIPv2 for support of IPv6. It uses UDP port 521 to send updates to the multicast group. It uses IPSec for authentication while RIPv2 supports RIPv1 for authentication.
link-state routing protocol - aka "telling the world about its neighbors"
It is one of the two main classes of routing protocols used in packet switching networks for computer communication. Two examples are OSPF and IS-IS. How it works: each router on a network independently prepares a routing table or map or path to other routers on the network. It shares only the connectivity related among the connected routers whereas the distance vector routing shares routing tables with their neighbors.
Border gateway protocol
It is the preferred and main protocol used in within Autonomous System, called "the glue of the Internet". It connects all AS' together. The current version is BGP-4. It is the distance-vector routing protocol. The AS-to-AS routers are called edge routers.
Intermediate System to Intermediate System (IS-IS)
Protocol similar to, but not as popular as, OSPF, but with support for IPv6 since inception. It uses the concept of areas and send only updates to routing tables.
Managed devices
Routers and advanced switches
