From: Richard Gallagher (rgallagh@cisco.com)
Date: Sat Jul 03 2004 - 10:43:38 GMT-3
Can you send:
- sh sys mtu
The sys mtu is not shown in the config, even it's not the default.
If you enable "debug ip os adj" on both side you will see the mtu that
each side is sending.
HTH, Rich
On Sat, 2004-07-03 at 15:37, barrerj1@hotmail.com wrote:
> 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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