The show ip protocols command displays the parameters and other information about the current state of any active IPv4 routing protocol processes configured on the router. The show ip protocols command displays different types of output specific to each routing protocol.
The output in Figure 1 indicates several EIGRP parameters, including:
1. EIGRP is an active dynamic routing protocol on R1 configured with the autonomous system number 1.
2. The EIGRP router ID of R1 is 1.1.1.1.
3. The EIGRP administrative distances on R1 are internal AD of 90 and external of 170 (default values).
4. By default, EIGRP does not automatically summarize networks. Subnets are included in the routing updates.
5. The EIGRP neighbor adjacencies R1 has with other routers used to receive EIGRP routing updates.
Note: Prior to IOS 15, automatic summarization was enabled, by default, for EIGRP.
The output from the show ip protocols command is useful in debugging routing operations. Information in the Routing Information Sources field can help identify a router suspected of delivering bad routing information. The Routing Information Sources field lists all the EIGRP routing sources the Cisco IOS software uses to build its IPv4 routing table. For each source, note the following:
- IPv4 address
- Administrative distance
- Time the last update was received from this source
As shown in Figure 2, EIGRP has a default AD of 90 for internal routes and 170 for routes imported from an external source, such as default routes. When compared to other IGPs, EIGRP is the most preferred by the Cisco IOS, because it has the lowest administrative distance. EIGRP has a third AD value of 5, for summary routes.