[j-nsp] Best practice MTU?

[Devin Kennedy]

Sent from my Samsung Galaxy Note™, an AT&T LTE smartphone

-------- Original message --------
Subject: Re: [j-nsp] Best practice MTU?
From: Jack Bates <jbates at brightok.net>
To: Chris Kawchuk <juniperdude at gmail.com>
CC: Re: [j-nsp] Best practice MTU?

I agree, as long as the transport between devices supports the MTU. This 
is especially important with device interoperability. Cisco, for 
example, apparently pads out ISO hello packets to MTU (Juniper limits it 
to maximum ISO packet size). If the packet is discarded by transport 
medium, the ISIS session will not come up. Found this one out increasing 
MTU by 4 to support a single MPLS tag. lol

Jack

On 4/26/2012 6:33 PM, Chris Kawchuk wrote:
> I usually set the interface physical MTU as high as it goes (per device), but manually set protocol inet to MTU 1500 (for things like OSPF to work). This allows for as-large-as-MTU-as-MPLS-can-do. Other address families aren't that picky about MTU matching.
>
>
> ge-1/0/5 {
>      description "LINK to another IP/OSPF/MPLS device - May or May not support MTU 9192 on the physical.... but inet4/OSPF is 1500 so it works";
>      mtu 9192;
>      unit 0 {
>          family inet {
>              mtu 1500;
>              address 10.102.10.1/24;
>          }
>          family mpls;
>      }
> }
>
> - CK.
>
>
>
> On 2012-04-27, at 7:32 AM, OBrien, Will wrote:
>
>> We've been pushing out jumbo frames across our new core lately. Right now I've got multiple boxes from multiple vendors that all support different maximum MTUs.
>>
>> Example: Juniper MX960/480, Nexus 7009, Nexus 5k/2k, Catalyst 4900, Nortel/Avaya 8600.... All different maximums.
>>
>> Anyone have suggestions for a best practice MTU? (That is.... over 9000?!)
>>
>>
>> Thanks!
>>
>> Will
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>
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