Effect Of "no ip cef optimize neighbor resolution" - Fix Bug CSCuo89272

[WGL_BK]

Hello all,

I've recently observed that our 3750x stack acting as core switch has been logging a lot of messages like below:

Jan 16 08:02:26.646: %ADJ-5-RESOLVE_REQ_FAIL: Adj resolve request failed for 10.0.10.145 on Vlan2

I've seen where this is supposedly a bug and can be fixed by "no ip cef optimize neighbor resolution". What effect does this have on the switch? How does it change ARP process? 

[curdubanbogdan]

Hello,

Any normal function of ARP won't be affected. 

Are you using routing on the switch? If not the no cef will not affect your switching functions.

BR

[WGL_BK]

Thanks for your reply. The switch does carry out routing, it is our core switch.  Can you say how we can expect the command to change its routing capabilities?

[curdubanbogdan · Accepted solution]

It does not affect routing. ip cef (Cisco Express Forwarding) has different functions for speed of packet process (l2 or l3) done in hardware. If you erase this command it will affect the speed of resolving arp for directly connected hosts, but not its functionality.

So cef neigh resolution means speed of arp done in hw using adj table. This is all.