IP Routing

Chapter 5. Routing Information Protocol Version 2 (RIP-2)

RIP Version 2 is not a new protocol -- it is RIP Version 1 with some additional fields in the route update packet, key among them being subnet mask information in each route entry. The underlying DV algorithms in RIP-2 are identical to those in RIP-1, implying that RIP-2 still suffers from convergence problems and the maximum hop-count limit of 16 hops. Hence, RIP-2 may not be your choice as the routing protocol for a large or mid-sized network with multiple paths between segments. However, the new features in RIP-2 may be compelling enough for you to consider migrating an existing RIP-1 network to RIP-2. The new features in RIP-2 are summarized here:

Subnet mask

RIP-2 updates carry the subnet mask in each route entry, making RIP-2 a classless routing protocol that supports Variable Length Subnet Masks (VLSM), discontiguous address spaces, and CIDR blocks.

Next hop IP address

RIP-2 updates carry the next hop IP address in each route entry. As we will see later, the next hop IP address is useful when routes are being redistributed between RIP-2 and another routing protocol.

Authentication data

Every RIP-2 packet can carry authentication data to validate the source of the RIP-2 update. Remember that RIP-1 has no security features -- any host transmitting on UDP port 520 will be believed by neighbors running RIP-1.

Route tag

RIP-2 updates carry a tag in each route entry that is not used by RIP but could be used to represent information ...