Allied Telesis AT-8100 Series - Manual (Page 1858)

Chapter 106: Routing Information Protocol (RIP)
1858
Enabling and Disabling Automatic Route Summarization
As a corporation grows, the corporate network needs to expand as well.
The number of entries in routing tables increases, and this growth costs
CPU resources, memory, and bandwidth used to maintain routing tables.
To reduce the size of routing tables and keep the network scalable, RIP
automatically summarizes network boundaries by default.
Note
You are allowed to disable automatic route summarization in RIP
Version 2. Automatic summarization is always enabled in RIP
Version 1.
Assume that you have the networks shown in Figure 287. The routing
interfaces in VLAN 50 are RIP enabled in both receiving and sending RIP
Version 2, and the networks in VLANs 10, 20, and 30 are associated with
RIP using the NETWORK command.
Figure 287. Automatic Summarization Example
RIP allows Switch S1 to summarize 10.10.10.0/24 and 10.10.30.0/24 into
10.10.0.0/16 route and advertises the summarized route to Switch S2.
However, if other subnets of 10.10.0.0/16 exist downstream in the
network, meaning that the network address is not contiguous,
summarization may not be ideal. In that case, you want to disable
automatic summarization.
The following example disables automatic summarization:
S1> enable
S1# configure terminal
S1(config)# router rip
S1(config-router)# no auto-summary