Technical data

BLADE OS 5.1 Application Guide
126
 Chapter 9: Routing Information Protocol BMD00136, November 2009
Routing Updates
RIP sends routing-update messages at regular intervals and when the network topology changes.
Each router “advertises” routing information by sending a routing information update every 30
seconds. If a router doesn’t receive an update from another router for 180 seconds, those routes
provided by that router are declared invalid. The routes are removed from the routing table, but they
remain in the RIP routes table. After another 120 seconds without receiving an update for those
routes, the routes are removed from respective regular updates.
When a router receives a routing update that includes changes to an entry, it updates its routing table
to reflect the new route. The metric value for the path is increased by 1, and the sender is indicated
as the next hop. RIP routers maintain only the best route (the route with the lowest metric value) to
a destination.
For more information, see the Configuration section, Routing Information Protocol Configuration
in the BLADE OS Command Reference.
RIPv1
RIP version 1 use broadcast User Datagram Protocol (UDP) data packets for the regular routing
updates. The main disadvantage is that the routing updates do not carry subnet mask information.
Hence, the router cannot determine whether the route is a subnet route or a host route. It is of limited
usage after the introduction of RIPv2. For more information about RIPv1 and RIPv2, refer to
RFC 1058 and RFC 2453.
RIPv2
RIPv2 is the most popular and preferred configuration for most networks. RIPv2 expands the
amount of useful information carried in RIP messages and provides a measure of security. For a
detailed explanation of RIPv2, refer to RFC 1723 and RFC 2453.
RIPv2 improves efficiency by using multicast UDP (address 224.0.0.9) data packets for regular
routing updates. Subnet mask information is provided in the routing updates. A security option is
added for authenticating routing updates, by using a shared password. BLADE OS supports using
clear password for RIPv2.
RIPv2 in RIPv1 compatibility mode
BLADE OS allows you to configure RIPv2 in RIPv1compatibility mode, for using both RIPv2 and
RIPv1 routers within a network. In this mode, the regular routing updates use broadcast UDP data
packet to allow RIPv1 routers to receive those packets. With RIPv1 routers as recipients, the routing
updates have to carry natural or host mask. Hence, it is not a recommended configuration for most
network topologies.
Note – When using both RIPv1 and RIPv2 within a network, use a single subnet mask
throughout the network.