RIP Version1

Characterstics of RIPv1 are as follows:
  • RIPv1 is Distance-vector protocol which uses well-known UDP port number 520.
  • RIPv1 is Classful protocol and doesn't support VLSM or CIDR. It means that RIPv1 is not provisioned to send the subnet mask of the prefix along with the update, however there is an exception to this concept if we use same Major class boundary. Kindly read the article RIP Behavior - Discontiguous Networks.
  • Metric is router hop count. Metric/Hop Count increases when update is received on inbound interface and not when it exits via outbound interface.
  • Maximum hop count is 15; unreachable routes have a metric of 16.
  • RIPv1 sends Periodic route updates broadcasted every 30 seconds.RIPv1 uses Broadcast addresses at both Layer 2 (FF:FF:FF:FF:FF:FF) and Layer 3 (255.255.255.255) for advertising. Kindly see the snapshot below:
  • RIPv1 can advertise 25 routes per RIP message.
  • RIPv1 Implements split horizon with poison reverse.
  • RIPv1 can also generate triggered updates using interface level command "R1(config-if)#ip rip triggered".
  • RIPv1 does not support for authentication.
  • Default Administrative distance for RIPv1 is 120. This can also be changed.
  • It is used in small, flat networks or at the edge of larger networks.


RIPv1 Packet Format:
  • Command: Describes the purpose of the packet. The RFC describes five commands, two of which are obsolete and one of which is reserved. The 2 used commands are:
             1. Request: Requests all or part of the responding router's routing table.
             2. Response: Contains all or part of the sender's routing table. This message might be a response to a request, or it might be an update message generated by                     the sender.
  • Version: Set to the value of 1 for RIPv1.
  • Address Family Identifier (AFI): Set to a value of 2 for IP.
  • IP address: The destination route/subnet/prefix. It might be a network address, subnet, or host route. Special route 0.0.0.0 is used for the default route.
  • Metric: A field that is 32 bits in length. It contains a value between 1 and 15, specifying the current metric for the destination. The metric is set to 16 to indicate that a destination is not reachable.
R1#show ip protocols
Routing Protocol is "rip"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Sending updates every 30 seconds, next due in 17 seconds
  Invalid after 180 seconds, hold down 180, flushed after 240
  Redistributing: rip
  Default version control: send version 1, receive version 1
    Interface             Send  Recv  Triggered RIP  Key-chain
    FastEthernet1/0       1     1
    Loopback0              1     1
  Automatic network summarization is not in effect
  Maximum path: 4
  Routing for Networks:
    10.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    10.10.12.2           120      00:00:23
  Distance: (default is 120)

If you have understood characteristics of RIPv1  and like this article, kindly share it with your friends.