[c-nsp] Catalyst6506 w/ sup1amsfc2 & 6148-ge-tx large packetsaredropped

[Church, Charles]

The dot1q header adds 4 bytes to the frame, making a frame of 1522 possible.  If you set that incoming L3 interface MTU to 1496, that should do it.  Assuming PMTUD is working right.

Chuck 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Comm-AG
Sent: Tuesday, October 09, 2007 6:55 AM
To: 'Brian Turnbow'; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Catalyst6506 w/ sup1amsfc2 & 6148-ge-tx large packetsaredropped

Brian,

Thanks for your input. Can you suggest a work-around for the problem that I
am having....should I set the MTU lower on the incoming L3 interface ?

At this point,  all applications which send large packets (1500 bytes) are
failing

Rgds,
Anthony

-----Original Message-----
From: Brian Turnbow [mailto:b.turnbow at twt.it] 
Sent: Tuesday, October 09, 2007 5:56 PM
To: Comm-AG; cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] Catalyst6506 w/ sup1amsfc2 & 6148-ge-tx large packets
aredropped

The 6148 supports up to 1518 frame size  , the 6148A does 9216.
This may be your problem
Regards
Brian
 

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Comm-AG
Sent: martedì 9 ottobre 2007 9.22
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Catalyst6506 w/ sup1amsfc2 & 6148-ge-tx large packets
aredropped

Hi,

 

I have a problem isolated to 6148-ge-tx line-card.  The line-card connects a
number of service provider connections.  When large packets are switched
between different ports on the same card,  large packets are dropped.

 

The problem has become apparent since our international service provider
(call it T-Systems) upgraded their CE router and required us to run dot1q on
the 6148-ge-tx interface.  Since then,  all traffic switched from other
sources to the T-Systems port has this problem where large packets are
dropped.

 

If we move services to another card leaving the T-Systems connection as it
was,  the problem goes away.

 

Any help would be appreciated.

 

Thanks

Anthony

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