Information Technology Reference
In-Depth Information
RIPv1
RIPv1 was defined in RFC 1058 (June 1988). RIP is a distance vector routing protocol that uses
router hop count as a metric. RIP is a classful routing protocol that does not support VLSMs or
classless interdomain routing (CIDR). Authentication is not supported in RIPv1. There is no
method for authentication of route updates. A RIP router sends a copy of its routing table to its
neighbors every 30 seconds. RIP uses split horizon with poison reverse; therefore, route updates
are sent out an interface with an infinite metric for routes learned (received) from the same
interface. The RIP standard was based on the popular routed program in UNIX systems in the
1980s. Cisco's implementation of RIP adds support for load balancing. RIP loads balance
traffic if there are several paths with the same metric (equal-cost load balancing) to a destination
RIP. Also, triggered updates are sent when the metric of a route changes. Triggered updates help
the network converge faster rather than having to wait for the periodic update. RIP also has an
administrative distance of 120; administrative distance is covered in Chapter 10,
“Administrative Distance, Access Lists, Route Manipulation, and IP Multicast.”
RIP automatically summarizes IP networks at network boundaries. A network boundary occurs
on a router that has one or more interfaces without an IP address that is part of the network num-
ber. Networks are summarized to their IP class. An IP network that uses 24-bit subnetworks
from 180.100.50.0/24 to 180.100.120.0/24 is summarized to 180.100.0.0/16 at a network
boundary. You can disable autosummarization with the
no auto-summary
command, as follows:
router rip
no auto-summary
RIPv1 Forwarding Information Base
The RIPv1 protocol keeps the following information about each destination:
•
IP address
—IP address of the destination host or network
•
Gateway
—The first gateway along the path to the destination
•
Interface
—The physical network that you must use to reach the destination
•
Metric
—A number that indicates the number of hops to the destination
•
Timer
—The amount of time since the entry was last updated
The database is updated with the route updates received from neighboring routers. As shown in
Example 7-1, the
show ip rip database
command shows the RIP database of a router.
Example 7-1
show ip rip database
Command
router9#show ip rip database
172.16.0.0/16 auto-summary
172.16.1.0/24 directly connected, Ethernet0
172.16.2.0/24
[1] via 172.16.4.2, 00:00:06, Serial0
Search WWH ::
Custom Search