From: Antonio Soares (amsoares@netcabo.pt)
Date: Tue Jul 10 2007 - 19:42:25 ART
Answer to my previous question: The lower MTU side only.
> But the way, when you have an OSPF Mtu Mismatch, where you do add the "ip
ospf mtu-ignore" command ?
> 1) The device with the lower Mtu.
> 2) The device with the higher Mtu.
> 3) Both devices.
From the command reference:
"OSPF checks whether neighbors are using the same MTU on a common interface.
This check is performed when neighbors exchange DBD packets. If the
receiving MTU in the DBD packet is higher than the IP MTU configured on the
incoming interface, OSPF adjacency will not be established."
Use "debug ip ospf adj" to help you understand what's going on.
This made me think about this scenario:
You are asked to establish an ospf adjacency with a Backbone router that you
don't control. You see that your router has the higher MTU.
Solution: decrease your mtu in order to match the other side :)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Antonio Soares
Sent: sabado, 23 de Junho de 2007 17:58
To: 'Radioactive Frog'; johngibson1541@yahoo.com
Cc: ccielab@groupstudy.com
Subject: RE: RE: MTU Mismatch in OSPF
+++++++++++++++++++++++++++++++++++++++++++++++++++
The 3560 default is 1500:
Switch#sh flash
Directory of flash:/
2 -rwx 7963038 Mar 1 1993 00:57:27 +00:00
c3560-advipservicesk9-mz.122-25.SEE2.bin
32514048 bytes total (24549888 bytes free) Switch# Switch# Switch#sh flash
+++++++++++++++++++++++++++++++++++++++++++++++++++
Directory of flash:/
2 -rwx 7963038 Mar 1 1993 00:57:27 +00:00
c3560-advipservicesk9-mz.122-25.SEE2.bin
32514048 bytes total (24549888 bytes free)
Switch#sh system mtu
System MTU size is 1500 bytes
System Jumbo MTU size is 1500 bytes
Routing MTU size is 1500 bytes
Switch#
+++++++++++++++++++++++++++++++++++++++++++++++++++
But the way, when you have an OSPF Mtu Mismatch, where you do add the "ip
ospf mtu-ignore" command ?
1) The device with the lower Mtu.
2) The device with the higher Mtu.
3) Both devices.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Radioactive Frog
Sent: sabado, 23 de Junho de 2007 5:23
To: johngibson1541@yahoo.com
Cc: ccielab@groupstudy.com
Subject: Re: RE: MTU Mismatch in OSPF
dats sound strange to me!
frog
On 6/23/07, johngibson1541@yahoo.com <johngibson1541@yahoo.com> wrote:
>
> I think 3550's MTU at 1504 is caused by a file flash:env_vars
>
> If I remove this file, then reload it will become 1500.
>
> My 3560 is a different story. It is 1504 by itself.
>
> Strangely, univercd keeps talking about 3560 and 3550 default mtu
> being 1500. They are just not saying the correct thing.
>
> 3560 at 12.2(25) , 12.2(35) , and the latest 12.2(37) all make the
> same mistake!
>
> ______________________________________________________________________
> _ Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:40 ART