[c-nsp] IOS ping response improvement

Ted Mittelstaedt tedm at toybox.placo.com
Tue Feb 14 03:10:57 EST 2006

Your PHB's are right, you should not be seeing this on a switch that is
doing nothing.  The
only time that any kind of traffic prioritization - ICMP or otherwise -
into effect is when you run out of resources - cpu resources, bandwidth,
whatever.  That then forces the device to start picking and choosing what
is going to be dropped and what is going to be delayed and what is going
to be responded to - that is the essense of prioritization.

Since this is a switch I would bet 10 to 1 that it's an autonegotiation
with your workstation ethernet chipset and the 2900XL switch port.  Is by
any chance your workstation running a gigabit adapter and your plugged
a 10/100 switch port?  Is it by any chance a Dell workstation with that
excrement broadcom gigabit ethernet chipset?  Do you realize if you gave
me a dollar every time I saw an ethernet problem with one of those shitty
chips that you would be bankrupt? :-)

Start by firmware updating your switch, then plug another workstation
an adapter from a different manufacturer in it, and retry your ping test.
make sure your using a good cable that was factory-crimped not something
that you built yourself.


>-----Original Message-----
>From: cisco-nsp-bounces at puck.nether.net
>[mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of Church, Chuck
>Sent: Monday, February 13, 2006 8:07 PM
>To: nsp
>Subject: [c-nsp] IOS ping response improvement
>    I'm facing an issue with missed SLAs regarding 2900XL switches and
>slow ping response to the mgmt interface at times.  I realize that ICMP
>is by design a low-priority thread.  But convincing that to our PHBs may
>be a large battle.  What I see on a locally attached switch with only 1
>port up (attached to my workstation) is about 80% of the responses are
>1-5 ms, but about 20% are in the 30-50ms range, which doesn't meet our
>SLAs for the LAN.  I'm sure the CPU is working on STP, CDP, etc,etc
>during these times.  But is there anything I can do to improve this?
>These switches only exist at the access layer, so STP is only of
>importance on the two uplink ports.  The 'scheduler interval' command
>only accepts down to 100ms, which isn't really helping.  I know this is
>purely cosmetic and not affecting the traffic one bit, but our managers
>don't like missing SLAs, even if they're not well-planned...
>Chuck Church
>Lead Design Engineer
>Netco Government Services - Design & Implementation Team
>1210 N. Parker Rd.
>Greenville, SC 29609
>Home office: 864-335-9473
>Cell: 864-266-3978
>cchurch at netcogov.com
>PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x4371A48D
>"I'm one Snickers Pie away from losing my foot to diabetes."  -  Homer
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