[j-nsp] Redundant RE question

[Jonas Frey]

Hi,

on a M20 with dual RE i get the following warning while commit
synchronize:

re0: configuration check succeeds
re1: 
[edit groups re1 interfaces fxp0 unit 0 family inet]
  'address 192.168.0.185/24'
    warning: [edit system backup-router] not present. The default route
for fxp0 is not installed.
commit complete
re0: commit complete

I've checked the docs but its still unclear to me what this exactly
means and how i can fix it (if it needs to be fixed).

Regards,
Jonas