Solved: CEF or Routing table !

illusion_rox · ‎08-02-2009

Dear All, i was going through this doc

http://www.cisco.com/en/US/tech/tk364/technologies_tech_note09186a0080093fdc.shtml

When we usually want to know the route for a network lets say 10.20.1.1, i usually do this

sh ip route 10.20.1.1.

After reading the above doc, if i have enabled cef, then which one is more accurate or should be put into practice

1) sh ip route x.x.x.x

or

2) sh ip cef x.x.x.x

Pls your input is highly appreciated, i also know that cef is an enhanced copy of routing table and after cef is enabled, is routing table is consulted at all ?

Roman Rodichev · ‎08-02-2009

"show ip route" shows RIB (routing information base) - aka control plane

"show ip cef" shows FIB (forwarding information base) - aka data plane

Routing Protocols and static routes are used to populate RIB. RIB information is used to update FIB. FIB is used to forward packets.

View solution in original post

Roman Rodichev · ‎08-02-2009

"show ip route" shows RIB (routing information base) - aka control plane

"show ip cef" shows FIB (forwarding information base) - aka data plane

Routing Protocols and static routes are used to populate RIB. RIB information is used to update FIB. FIB is used to forward packets.

illusion_rox · ‎08-02-2009

Dear Roman, thanks alot for the feedback. So when checking the route which one should be used

sh ip route

or sh ip cef ?

Kindly confirm my point,

Jon Marshall · ‎08-03-2009

As Roman said, the RIB is used to update the FIB so using "sh ip route" is the way to go.

Only if traffic is not routing the way it should be would you then start to investigate the CEF adjacencies.

Jon