Maximum throughput of 3,640?

Hello,

I have a Cisco-3,640 with dual FastEthernet card. It does routing between the two interfaces, and I've found that at 50Mb/sec the CPU usage is 100% (most of it in interrupt mode). I've enabled CEF and IP ROUTE-CACHE, removed the access lists but it still the same bottleneck. Is this the maximum that this router can get to?

Thanks, __Yehavi:

Above is an excellent document.

How much is not at interrupt level?

Check that you are not doing unnecesary local routing. i.e. maybe allow ICMP Redirects.

On a hard pressed router make sure that it is not getting hit with a lot of broadcasts. For many purposes you can filter all IP broadcasts with an ACL (maybe you need to allow DHCP).

access-list might be

permit dhcp (don't know exact command right now) deny ip any host 255.255.255.255 deny in any host x.x.z.255 ! x.y.z for local subnet permit ip any any

Might be worth trying CEF and plain fast switching.

conf t

! for CEF

ip cef ! or os if just cef?

int fast x ip router-cache cef ! repeat for all interfaces

! for fast switching

conf t no ip cef

int fast x no ip route-cache cef ip route-cache ! repeat for all interfaces

I know that some people assume that CEF is best but if it were me I would check.

As mentioned by me a few minutes ago in another thread try to get rid of buffer allocations and frees.

If you like post sh buffers

I now do not hesitate to increase buffers manually to prevent misses and failures provided that there is SUFFICIENT MEMORY if I suspect that a router is under any kind of stress and shows significant misses or failures.

3640 is not a fast router by current standards. 50,000 - 70,000pps 25.6 - 36Mbps

These are very conservative numbers since Cisco assume

64byte packets and to get 200Mbps (i.e. Full Duplex 100M) you will need an average packet size of

(200,000,000/8)/50,000 bytes = 500 bytes