From: Church, Chuck (cchurch@wamnetgov.com)
Date: Sat Jul 03 2004 - 10:52:36 GMT-3
What exactly do you mean by 'running between them'? Is OSPF running on
the 3550 also, or just on the two routers attached to it, meaning the
3550 is just providing two ports in the same VLAN for these two routers?
Send us a 'sh ip int' from the 2 (if the 3550 is just a passthrough) or
more (if the 3550 is running OSPF) interfaces involved.
Chuck Church
Wam!Net Government Services - D&I Team
Lead Design Engineer
CCIE #8776, MCNE, MCSE
1210 N. Parker Rd.
Greenville, SC 29609
Office: 864-335-9473
Cell: 703-819-3495
cchurch@wamnetgov.com
PGP key:
http://pgp.mit.edu:11371/pks/lookup?op=index&search=cchurch%40wamnetgov.
com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
barrerj1@hotmail.com
Sent: Saturday, July 03, 2004 9:38 AM
To: ccielab@groupstudy.com
Subject: RE: OSPF MTU problem
Thanks for your reply guys!
I did not changed the system MTU
I don't' see it at the top of the config
The rack I'm using is from a rental place.
SW1#sh run
Building configuration...
Current configuration : 3309 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname SW1
!
enable password cisco
!
ip subnet-zero
ip routing
ip rcmd rsh-enable
ip rcmd remote-host R6 140.1.6.6 R6 enable !
no ip domain-lookup
ip ssh time-out 120
ip ssh authentication-retries 3
!
spanning-tree mode pvst
spanning-tree extend system-id
!
!
!
****************************
I'm doing dot1q trunking between the Switches, but the interfaces in
play are directly connected to the Sw1
So If I did not changed the MTU they why the OSPF is bitching about
incorrect OSPF MTU when I do a debug ip routing
Thanks
JB
-----Original Message-----
From: Nigel.Johnson@barclayscapital.com
[mailto:Nigel.Johnson@barclayscapital.com]
Sent: Saturday, July 03, 2004 7:41 AM
To: barrerj1@hotmail.com; ccielab@groupstudy.com
Subject: RE: OSPF MTU problem
Check that you haven't changed the 'system mtu' on one of the 3550's.
This
will appear towards the top of the running config.
Cheers,
Nigel
CCIE# 13514
-----Original Message-----
From: samccie2004@yahoo.co.uk [mailto:samccie2004@yahoo.co.uk]
Sent: 03 July 2004 13:07
To: barrerj1@hotmail.com; ccielab@groupstudy.com
Subject: RE: OSPF MTU problem
Are iu trunking , if so u might be adding more to MTU due to dot1q.
Just a guess, pls correct me if I am wrong.
Sam
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
barrerj1@hotmail.com
Sent: 03 July 2004 13:26
To: ccielab@groupstudy.com
Subject: OSPF MTU problem
Hi all!
While doing an OSPF practice lab, I was encountered by the following
problem.
2 routers connected to a 3550 and running OSPF between them, the state
was
stuck in EXSTART and couldn't complete the adjacency.
I checked CCO and found that the problem was an MTU mismatched. However,
the
CCO doc points this problem to be a common when you connect to another
vendor's router. In my case all devices are CISCO.
Neighbors Stuck in Exstart/Exchange State
The problem occurs most frequently when attempting to run OSPF between a
Cisco router and another vendor's router. The problem occurs when the
maximum transmission unit (MTU) settings for neighboring router
interfaces
don't match. If the router with the higher MTU sends a packet larger
that
the MTU set on the neighboring router, the neighboring router ignores
the
packet.
http://www.cisco.com/en/US/tech/tk365/tk480/technologies_tech_note09186a
0080093f0d.shtml
Can any one explain why this behavior as I did not change any of the MTU
configurations before the problem occurred?
Thanks
JB
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