[f-nsp] Determining the load on the ip-forwarding engine on a Bigiron

[Brent Van Dussen]

Hello Gunter,

In terms of load we have always just had to keep an eye on the 
forwarding-cache size to get a gauge for when the switch is going to start 
having trouble.

Since most of the forwarding is done in hardware at line-rate for all 
prefixes when net-aggregate is turned on, there usually isn't an 
issue.  When you start to run into net-agg ineligibles, this necessitates 
the use of the CPU on the management card to keep track of and forward the 
non conforming packets.  Since the CAM isn't big enough to carry all 
internet host's as separate entries, the CPU keeps track of them in a 
slower DRAM location that we call the ip-cache table ( 'show ip cache' ).

So compare your current ip cache size with that of your maximum configured 
ip-cache size and you have a rough idea where you are at.  Kind of an 
apples to Oranges comparison since a bigiron works nothing like a GSR does.

I am not sure if CPU manipulation of the ip cache gets computed in with the 
"IP" section of show proc cpu, maybe a kind foundry developer can let us 
know :)

-Brent

At 11:30 AM 10/23/2005, Gunther Stammwitz wrote:
>Hello colleagues,
>
>we're using several foundry Bigirons - some Ironcore and some Jetcore - 
>and I'd like to find out how much load there is on the ip-forwarding-engine.
>On most Cisco routers one can check the cpu load of the Linecard but on a 
>foundry forwarding is done in hardware. Is there any way to find out how 
>much room there is left and how high the utilization is?
>
>As far as I understand a forwarding engine can usually forward x mpps with 
>a specific packet size which equals y megabits per second but much less 
>megabits if the packet size is smaller.
>
>Any ideas?
>I've seen show proc cpu and one can read 
>"IP               0.19      0.13      0.13      0.15        4518345" there 
>but I guess this means how much cpu of the management card is being used 
>by icmp-replies addressed to the router itself?!?
>
>Thanks,
>Gunther
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