Message format RIP-1 message format contains a number of “must be zero” fields, these fields are used by RIP-2’s extended functionality. These fields are Routing Domain (2 bytes), Route Tag (2 bytes), Subnet Mask (4 bytes) and Next Hop (4 bytes). The Version field contains a value of 1 for RIP-1 message and 2 for RIP-2. |
Routing per Subnet RIP-1 supported subnet entries only within the subnetted network. This enforces strict hierarchical routing. RIP-2 allows routing on the subnet outside of the network by passing subnet mask information in parallel with the address. This also allows support of variable length masks within the same network or aggregation of several class-C addresses within one address group. |
Authentication RIP-1 is not a secure routing protocol. Any host sending packets from UDP port 520 would be regarded a router and trusted by its neighbours. RIP-2 includes an authentication procedure, which specifies that the first entry in a packet replaced by an “authentication segment”. The packet will contain a 32-bit command, an “address family identified” of 0xFFFF, an “authentication type” that identifies the algorithm in use, 16 bytes of authentication data, and then 24 destination-metric pairs. |
Routing Domains, Next Hop RIP-2 supports multiple autonomous systems on the same wire by using a 16-bit “Routing Domain” number. A route identifies whether the destination network of a packet by examining this field. RIP-2 also includes a “Next Hop” field to indicate the best relay hop for the other logical network on the same wire. |
Multicast RIP-1 uses a broadcast address to send routing advertisements to all nodes on the same wire. RIP-2 utilises a class-D address (224.0.0.9) for periodic multicasts. This effectively prevents other non-router hosts on the same wire from receiving routing messages. |
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