Overview of RIP
Routing Information Protocol (RIP) is an IP route exchange protocol that uses a
distance vector
(a number
representing distance) to measure the cost of a given route. The cost is a distance vector because the cost often
is equivalent to the number of router hops between the routing switch and the destination network.
A routing switch can receive multiple paths to a destination. The software evaluates the paths, selects the best
path, and saves the path in the IP route table as the route to the destination. Typically, the best path is the path
with the fewest hops. A hop is another router through which packets must travel to reach the destination. If the
routing switch receives an RIP update from another router that contains a path with fewer hops than the path
stored in the routing switch's route table, the routing switch replaces the older route with the newer one. The
routing switch then includes the new path in the updates it sends to other RIP routers, including routing switches.
RIP routers, including routing switches, also can modify a route's cost, generally by adding to it, to bias the
selection of a route for a given destination. In this case, the actual number of router hops may be the same, but
the route has an administratively higher cost and is thus less likely to be used than other, lower-cost routes. A RIP
route can have a maximum cost of 15. Any destination with a higher cost is considered unreachable. Although
limiting to larger networks, the low maximum hop count prevents endless loops in the network.
The switches support the following RIP types:
• Version 1
• V1 compatible with V2
• Version 2 (the default)
NOTE:
If the routing switch receives an ARP request packet that it is unable to deliver to the final
destination because of the ARP timeout and no ARP response is received (the routing switch knows
of no route to the destination address), the routing switch sends an ICMP Host Unreachable
message to the source.
Configuring RIP parameters
Use the following procedures to configure RIP parameters on a system-wide and individual VLAN interface basis.
Enabling RIP
RIP is disabled by default. To enable it, use one of the following methods. When you enable RIP, the default RIP
version is RIPv2-only. You can change the RIP version on an individual interface basis to RIPv1 or RIPv1-or-v2, if
needed.
Syntax:
[no] router rip
To enable RIP on a routing switch, enter the following commands:
switch(config)# ip routing
switch(config)# router rip
switch(rip)# exit
switch(config)# write memory
Chapter 8
Routing Information Protocol (RIP)
Chapter 8 Routing Information Protocol (RIP)
169
