tailieunhanh - 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. | Page 94 Wednesday January 9 2002 12 25 PM CHAPTER 5 Routing Information Protocol Version 2 RIP-2 In this chapter Getting RIP-2 Running RIP-2 Packet Format RIP-1 RIP-2 Compatibility Classful Versus Classless Routing Protocols Classful Versus Classless Route Lookup Authentication Route Summarization Summing Up 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 RIP11 implying that RIP-2 still suffers from convergence problems and the maximum hopcount limit of 16 hops. Hence RIP-2 may not lee your choíce as the routing protocol for a large or mid-sized network with multiple paths between segments. Howvver 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 wlll eee 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 rransmt--ting 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 such as the source of the route when the route is imported from another AS for example BGP . 94 Page 95 Wednesday January 9 2002 12 25 PM These additions to the RIP-1 update take the place of the unused or must be zero octets