Juniper: Using FXP0 as a routed interface

WARNING -- THIS IS ALMOST ALWAYS A BAD IDEA!!!!

The FXP0 interface (on the front of the routing-engine) is designed to be use for OOB access only and usually does not route. 

For emergency use you may be able to make if route by doing the following:

sysctl -w net.pfe.transit_re=1 

Keep in mind that the packet forwarding is then performed by the routing engine itself (the control plane). This means that:

  • Your CPU will run hot
  • Forwarding will be slow
  • Under load your protocols might not converge
  • Lots of other unhappy things will happen

Only use this for low speed, emergency use.