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wuh
New Member

TCP bad checksum erro message

One of our switches keeps generating an error message pasted below every a couple of minutes. And I did some research on Cisco website; it recommends that no action is to be done. But I still think there is anything I need to do to get rid of this message. Any ideas?

Thanks,

Han

5 REPLIES

Re: TCP bad checksum erro message

Hi Han

Can you post the full error message here ?

regds

wuh
New Member

Re: TCP bad checksum erro message

Hey, spremkumar,

I just copied the logging buffer.

Thanks,

Han

r-1046-1> (enable) sh logg buff

2007 Jun 07 06:14:36 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:16:37 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:18:37 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:20:37 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:22:37 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:24:36 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:26:36 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

2007 Jun 07 06:28:37 edt -04:00 %IP-3-TCP_BADCKSUM:TCP bad checksum

Cisco Employee

Re: TCP bad checksum erro message

Which switch and CatOS version you are using. Please paste " show version " from the switch.

When are you getting these messages. While you are telnetting the switch or connecting console to it.

Error Message:

IP-3-TCP_BADCKSUM:TCP bad checksum

Explanation:

This message indicates that the system has received a TCP packet with a bad checksum from another device on the administrative VLAN. The packet will be discarded.

Recommended Action:

No action is necessary. This message is provided for information only.

This message indicates that the system has received a TCP packet with a bad checksum from

another device on the administrative VLAN. The packet will be discarded.The error messages do not really affect the behaviour of the switch, since it merely drops these bad packets. owever, it is good to know where it originates and why it is sending

this bad packets.

One way of determining where this bad packets came from, you need to sniff the

administrative vlan or traffic destined to sc0. Please note that this is not an issue with

the switch, however the switch is simply reporting the error. The only way you can track this is via a sniffer.

I would suggest that you sniff the sc0 interface to see where those packets are coming from. I'd suggest to do this for both catalysts and let the capture run until you get several of these error messages: both>

HTH,Please rate if it does.

-amit singh

wuh
New Member

Re: TCP bad checksum erro message

Amit:

thanks, it does give some inconvenience to us since it generates the message every 1-2 minutes.

thanks,

Han,

1> (enable) sh ver

WS-C4006 Software, Version NmpSW: 6.3(10)

Copyright (c) 1995-2002 by Cisco Systems, Inc.

NMP S/W compiled on Nov 4 2002, 17:43:34

GSP S/W compiled on Nov 04 2002, 16:01:37

System Bootstrap Version: 5.4(1)

Hardware Version: 3.2 Model: WS-C4006 Serial #: FOX053701QW

Mod Port Model Serial # Versions

--- ---- ---------- -------------------- ---------------------------------

1 2 WS-X4013 JAB0543073P Hw : 3.2

Gsp: 6.3(10.0)

Nmp: 6.3(10)

3 48 WS-X4148-RJ45V JAE07110B57 Hw : 2.6

5 48 WS-X4148-RJ45V JAE071200AD Hw : 2.6

DRAM FLASH NVRAM

Module Total Used Free Total Used Free Total Used Free

------ ------- ------- ------- ------- ------- ------- ----- ----- -----

1 65536K 33357K 32179K 16384K 12946K 3438K 480K 216K 264K

Uptime is 21 days, 13 hours, 36 minutes

wuh
New Member

Re: TCP bad checksum erro message

amit:

The switch and my pc are one different side of a WAN link. What would you think is a better tool in this case for sniffing? RSPAN or RMON?

thanks,

Han,

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