ROUTING PROTOCOLS

Definitions

Administrative Distance (AD) is a measure of trustworthiness, rated on a scale of 0 to 255, used by routers to select the best path, when multiple, different routing protocols provide routes to the same destinations.

Routing by rumor – distance vector  routing algorithm, that passes its complete routing table contents to neighbor router.

Round-robin load balancing – distance vector uses only hop counts to determine the best path to a network.

Classes of routing protocols

Distance Vector (RIP, RIP2, IGRP)

Link State (OSPF, IS-IS)

Hybrid (EIGRP, BGP)

Distance Vestor Routing Protocols

Routing Information Protocol (RIP)

• It sends complete routing table out to all active interfaces every 30 seconds.
• Maximum allowable hop count is 15 by default
• Works well in small networks
• Only classful routing – all devices in network muss use the same subnet mask for each specific address class.

Disadvantages:

• Creates routing loops – that ist the reason for 15 hop counts
• Is slow at converging (latency in network)

RIP Version 2 (RIPv2)

• Is considered as classless routing protocol, which means that it sends subnet mask information along with route update
• Can support variable length subnet masks (VLSMs)

Variable-length subnet masks (VLSMs)

• We can have different subnet masks for different router interfaces
• Is a networking technique that enables to devide an IP address utilization
• Requires routers to support classless routing protocols (OSPF, EIGRP, RIPv2)