Introduction
This document describes the syslog message %IPRT-3-RIB_LOOP: Resolution loop formed by routes in RIB.
Explanation
The syslog message %IPRT-3-RIB_LOOP: Resolution loop formed by routes in RIB means that a routing loop was introduced into the Routing Information Table (RIB), the routing table of the router when it resolves routes. The cause of this could be a change in the network topology (for example, an interface flap), a normal temporary routing convergence event, or a misconfiguration.
If the error is temporary/transient, this might be perfectly normal during a routing convergence. If this is persistent, it needs investigation.
An example of how a routing loop can be formed due to bad configuration and operation is explained in show ip route loops.
Recommended Action
Complete these steps:
- Enter the show ip route loops command in order to identify which routes are involved and how the loop occurred.
- Check what recent changes were made to the network and/or routing protocols.
- Try to correct the misconfiguration, if any.
- Check for possible known defects with loops in the RIB for the specific Cisco IOS® version.
- Check for side effects, such as continuous high CPU and route churn in the RIB.
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