[j-nsp] MTU issues.

[Servet Erkün]

Nilesh is right  I think , in juniper you specify only payload size ,
in cisco you specify full frame size (ip header+icmp header+Payload)

servet



----- Original Message ----- 
From: "Ahmed Abdelghany" <aaeg202 at yahoo.com>
To: "Nilesh Khambal" <nkhambal at juniper.net>; "Flavio Schappo" 
<fschappo at gmail.com>
Cc: <juniper-nsp at puck.nether.net>
Sent: Tuesday, March 17, 2009 1:39 PM
Subject: Re: [j-nsp] MTU issues.


I think it is inversed, cisco add the IP headers to the size you specified, 
and juniper include the IP header in the size you specified.

 the problem appears when the packet arrives juniper interface with packet 
size larger than the interface MTU, which will drop the packet, while if 
this happened with cisco interface, it will fragment the packet.

Juniper will fragment the packet when it arrives on interface with large MTU 
and leaves on interface with MTU smaler than the packet size.


thanks
Abdelghany


________________________________
From: Nilesh Khambal <nkhambal at juniper.net>
To: Flavio Schappo <fschappo at gmail.com>
Cc: juniper-nsp at puck.nether.net
Sent: Monday, March 16, 2009 8:27:55 PM
Subject: Re: [j-nsp] MTU issues.

Cisco includes ip and icmp header size in the total specified packet
size. Payload in the case is 1510-20-8 = 1482 bytes. Juniper adds icmp
and ip header to the payload size you specify. So 1510 becomes 1538
bytes of ip packet.

Thanks,
Nilesh




On Mar 16, 2009, at 11:22 AM, "Flavio Schappo" <fschappo at gmail.com>
wrote:

> Hi
>
> Anybody have some explanation doc about MTU diferences between
> JUNIPER and
> CISCO?
>
> I think that I´m hitting some MTU issues where I have 2 ciscos worki
> ng ping
> with more them 1510 bytes and 2 Juniper or 1 juniper and 1 cisco are
> not
> working.
>
> Regards
>
> Flavio
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