Next Hop; Multicasting; Route Summaries - Juniper IGP - CONFIGURATION GUIDE V11.1.X Configuration Manual

Next Hop

The Next Hop field in a RIP message contains the next IP address where a packet is
sent. A value of zero in this field indicates that the next address the packet should
be sent to is the router that originally sent the RIP message.

Multicasting

To reduce unnecessary load on hosts that are not listening to RIPv2 messages, an IP
multicast address is used for periodic broadcast messages. The IP multicast address
is 224.0.0.9.

Route Summaries

You can summarize routes reported by RIP to reduce the size of the routing table
and the amount of traffic resulting from RIP updates. Configuring a RIP summary
will cause that prefix to be advertised with the associated metric regardless of the
presence of more-specific prefixes. Any more-specific prefixes will not be advertised
when they are covered by the summary. You can choose the degree of summarization
by using a prefix tree to specify the number of bits to report for routes matching a
route map. Alternatively, you can explicitly specify routes for RIP to summarize.
The following example shows how to configure a 16-bit route summary:
Prefix Tree Example
1.
2.
3.
This example summarizes routes for networks addressed by 2.1.x.x. The first 16 bits
of the network address are preserved in the summary. For example, routes 2.1.3.0,
2.1.2.0, and 2.1.1.0 would all be summarized as 2.1.0.0.
Specify a route map for RIP in Router Configuration mode.
host1#configure t
Enter configuration commands, one per line. End with CNTL/Z.
host1(config)#router rip
host1(config-router)#route-map 1
host1(config-router)#exit
Define a route map associated with a prefix tree.
host1(config)#
host1(config)#route-map 1
host1(config-route-map)#match-set
host1(config-route-map)#match-set summary prefix-tree boston
host1(config-route-map)#exit
host1(config)#
Set the conditions for summarization in the prefix tree, including which routes
are summarized and how many bits of the network addresses are preserved as
the network prefix.
host1(config)#ip prefix-tree boston permit 2.1.0.0/16
Chapter 4: Configuring RIP
209
Features