Description

This article describes the issue of the 'show interface terse' command displaying fabric interface IP addresses with 30.0.0.0/8 addresses.

Symptoms

Fabric interface IP addresses are system-determined and not configurable. The following is a excerpt of the output of  'show interface terse' :

fab0 up up
fab0.0 up up inet 30.17.0.200/24
fab1 up down
fab1.0 up down inet 30.18.0.200/24
fxp0 up down

Solution

  • This is expected behavior of the system.
  • These addresses are used only for the internal communication of the cluster.
  • No routes are installed for the fab0 subnets; it will not affect any transit traffic.

If, for whatever reason, a fabric interface was accidentally plugged into a production segment, the fabric traffic would still not be routed out, as it would not get processed at layer 2.