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Posted by on November 5, 2006, 5:45 pm
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Joop van der Velden wrote:
> Yehavi Bourvine (58-4279) wrote:
>
> > 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?
>
> Yep. See for example:
> http://www.cisco.com/warp/public/765/tools/quickreference/routerperformance.pdf
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.
>From the posted link
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
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