Troubleshooting BGP Best-Path Calculation Issues

Troubleshooting BGP Best- Path Calculation Issues

Chapter 14 discusses in detail how the BGP best-path algorithm works to select a single best route out of many to install in the IP routing table and to advertise to other BGP neighbors. This section discusses a few cases that deal with scenarios in which best-path selection does not work as intended.

The following are the cases discussed in this section:

• When the router ID (RID) selects the best path, BGP does not always select the lowest RID path as best, as described in the best-path algorithm.

• Two BGP neighbors in the same AS advertise a different MED for the same prefix, but the lowest MED is not selected as best, as described in the best-path algorithm.