[c-nsp] ip cef optimize neighbor resolution

[Lincoln Dale]

hi Ross,

Ross Vandegrift wrote:
> Hi everyone,
>
> Has anyone running SXH on a SUP720-3B(-XL) series 6500 tried "ip cef
> optimize neighbor resolution"?
>
> Cisco's docs seem to offer the usual tautologous explanation, and as a
> bonus, include a circular reference:
>   
LOL, classic.
> Both indicate that it triggers "Layer 2 address resolution of neighbors
> directly from Cisco Express Forwarding for IPv[46]".
>
> Has anyone tried this?  It sounds like this could be a win for a pair
> of 6500s I have with unexplainable high RP utilization problems - the
> boxes terminate a lot of VLANs and have a lot of ARP responsibilities.
> But I can't really find much discussion of it.
>   

the feature is essentially an enhancement for how CEF Gleans and the 
like are handled.
if you're familiar with how those kinds of things work, they would 
typically need to punt to software to resolve a (not yet available) 
adjacency through ARP or similar.

the enhancement/optimization here is that it can do it with fewer CPU 
cycles.

as to whether this would help in your scenario, its certainly a 
possibility.  but unless what you're seeing is a relatively short period 
of higher CPU during ARP / IP to MAC discovery, me thinks you may want 
to look into what your ARP aging timers are relative to your MAC aging 
timers.



cheers,

lincoln.