summary (RIP)
Function
The summary command enables RIP classful summarization. The summarized routes are advertised using natural masks.
The undo summary command disables classful summarization so that routing between subnets can be performed. The subnet information is then advertised. Route summarization reduces the routing table size.
By default, classful summarization is enabled for RIP-2.
Parameters
| Parameter | Description | Value |
|---|---|---|
| always | Enables classful summarization no matter whether split horizon is configured. | - |
Usage Guidelines
RIP-1 does not support classful summarization. When using RIP-2, you can use the undo summary command to disable classful summarization.
RIP-2 route summarization improves scalability and efficiency on large networks. IP address summarization means that there is no sub-routing entry in the routing table. That is, there is no routing entry composed of single IP address. In addition to reducing the routing table size, route summarization enables the switch to handle more routes.
When classful summarization is enabled, the switch summarizes subnet addresses to the natural network segment border while advertising routes to the natural network segment border. When split horizon or poison reverse is enabled, route summarization will be invalid if the always parameter is not specified. When summarized routes are sent outside the natural network segment, split horizon or poison reverse must be disabled.
- By default, classful summarization is enabled for RIP-2. If split horizon or poison reverse has been configured, classful summarization is invalid. When summarized routes are sent to the network border, split horizon and poison reverse must be disabled.
- The summary always command can enable classful summarization no matter whether split horizon or poison reverse is enabled.
The summarization preference on interfaces is higher than the summarization preference in RIP processes. That is, the preference of rip summary-address is higher than the preference of summary. When summarization is configured on both interface and RIP process, the summarized route is advertised only when a few specific routes are beyond the summarization range configured on the interface.