[c-nsp] Ouput Drops - 6500...

[Eli Dart]

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Church, Chuck wrote:
> Are the drops on a physical interface, or a VLAN int?  If you're trying
> to put all 700mbit/sec (which is an average) out on one physical
> interface, there a good chance there are frequent bursts above 700mbit,
> maybe even approaching the 1gig limit.  Those gig ports only have a
> small (~1 mbyte or so) buffer, so they don't queue stuff for too long.

Have you looked at the hold-queue command?  I seem to remember that the
box won't use all the buffer space available unless it's configured to
allow enough packets in the interface's output queue.

The default (I think) is 40 packets, which is pretty small in the face
of GigE bursts....

		--eli


> Those bursts are probably the cause.  If you can easily bump up one of
> the links to a 2-port etherchannel, that might fix it there.
> 
> 
> Chuck Church
> Lead Design Engineer
> CCIE #8776, MCNE, MCSE
> 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 
> 
> 
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Brian W.
> Gemberling
> Sent: Wednesday, November 02, 2005 3:08 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Ouput Drops - 6500...
> 
> 
> Hello,
> 
>  	We are currently getting output queue drops on one of our 6500's
> 
> w/ SUP2 MSFC2.  We are running Native IOS and the card is a 6416-GBIC.
> We 
> turned off routing and went directly to switching only, however, we
> still 
> got output queue drops.  I think I already know the answer to this, but 
> I'll ask anyways.  If we converted back to CatOS and ran strictly L2
> only, 
> would we still have the same issues?  Traffic levels are about 700mbit/s
> 
> in on one gig-e port on the 6416, and was in turn going out the SUP2
> gig-e 
> ports where it was getting output drops.  Any insight would be 
> appreciated.
> 
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- --
Eli Dart
ESnet Network Engineering Group
Lawrence Berkeley National Laboratory
PGP Key fingerprint = C970 F8D3 CFDD 8FFF 5486 343A 2D31 4478 5F82 B2B3
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