Improvement of RIP-V2 Protocol

People who learn routing know that the RIP routing protocol is one of the earliest routing protocols, so no matter which protocol is later, it is based on this improvement. So now we mainly introduce some characteristics of RIP-V2 protocol. It only adds some extension features based on the r12001 protocol to apply to the routing selection environment of modern networks. These extension features include:

◆ Each route entry carries its own subnet mask

◆ Route selection and update are more authenticated

◆ Each route entry carries the next hop address

◆ External route mark

◆ Multicast route update

The most important thing is that the route update entry adds the subnet mask field, so the RIP Protocol can use a variable length subnet mask, so that the RIP-V2 Protocol becomes a classless routing protocol ｡

Working principle of RIP-V2 Protocol

The V1 route update is broadcast. The RIP-V2 protocol uses multicast to send update packets to other vrouters that advertise the RIP-V2. The multicast address it uses is the reserved D-class address 224.0.0.9

The advantage of the multicast method is that the RIP route connected to the local network selects irrelevant devices and no longer takes time to parse the update packets broadcast on the vro ｡

Frame format of RIP-V2 Information

Including: Command (8-bit), version (8-bit), unused (value: 0), address family identifier, route tag, IP address, subnet mask, next hop, and measurement value. Like r12001, update packets for the RIP-V2 protocol can contain up to 25 route entries. Similarly, UDP 520 port numbers are used, and the maximum size of data packets is 512 8-bit ｡

◆ COMMAND -- values: 1 and 2. 1 indicate request information, and 2 indicate Response Message.

◆ VERSION (VERSION) -- this field value is 2 for the RIP-V2 Protocol

◆ Address family indentifier (AFI) -- set IP to 2. this field is set to 0 when the message is a request to select the entire router (or host) route table.

◆ ROUTERTAG) -- provide this field to mark an external route or to re-allocate the route to the RIP-V2 protocol. By default, this 16-bit field is used to carry the autonomy of the route injected from the external route selection protocol to the RIP system number. Although the RIP Protocol does not use this field, however, external routes connected to a certain RIP domain in multiple locations, you may need to use this routing label field to exchange route information through the RIP domain. This field can also be used to organize external routes into a "group" for easier control of these routes in the RIP domain ｡

◆ Ip address: the destination ADDRESS of the route entry. It can be the primary network ADDRESS, subnet ADDRESS, or host route ｡

◆ Subnet mask (subnet mask): A 32-bit MASK of the network and SUBNET of the IP address ｡

◆ Next hop (next hop) -- if it exists, it identifies a better address than the advertised router. That is, the next hop address it points out, the measurement value is closer to the destination than the advertised router on the same subnet. If this field is set to 0 (0.0.0.0), The advertised router address is the best next hop address ｡

◆ Measurement (METRIC) -- is a 1 ~ The number of hops between 16 ｡