[j-nsp] IPv6 MTU issue

[Gökhan Gümüş]

Thanks Alex.

Let me give a shot on this.

Gokhan

On Fri, Oct 21, 2011 at 2:00 PM, Alex <alex.arseniev at gmail.com> wrote:

> **
> It should, in my view.
> Rgds
> Alex
>
> ----- Original Message -----
> *From:* Gökhan Gümüş <ggumus at gmail.com>
> *To:* Alex <alex.arseniev at gmail.com>
> *Cc:* juniper-nsp at puck.nether.net
> *Sent:* Friday, October 21, 2011 12:57 PM
> *Subject:* Re: [j-nsp] IPv6 MTU issue
>
> Dear Alex,
>
> Thanks for the response.
> Yes, you are right.
> This service is configured on MX on logical router.
> There is an aggregated interface is trunked to a switch as seen below,
>
> abc> show configuration logical-systems tcr1 interfaces ae2.39
> vlan-id 39;
> family inet {
>     address a.b.c.d/30;
> }
> family inet6 {
>     address ..../124;
>
> Do you think that just to increase INET6 MTU to 1504 bytes resolves this
> issue?
>
> Thanks,
> Gokhan
>
>
> On Fri, Oct 21, 2011 at 1:51 PM, Alex <alex.arseniev at gmail.com> wrote:
>
>> My wild guess is that you are hitting a network of FreBSD/Olive/Linux IPv6
>> routers with certain cards where when 802.1Q is enabled, MTU is
>> automatically reduced by 4 bytes.
>> You can simulate it with Olive by enabling "vlan-tagging" on Intel PRO/100
>> card.
>> My $0.02
>> Thanks
>> Alex
>>
>>
>> ----- Original Message ----- From: "Gökhan Gümüs" <ggumus at gmail.com>
>> To: <juniper-nsp at puck.nether.net>
>> Sent: Friday, October 21, 2011 11:25 AM
>> Subject: [j-nsp] IPv6 MTU issue
>>
>>
>>  Dear all,
>>>
>>> I have an issue with IPv6 MTU.
>>>
>>> When i make a traceroute to one destination, the MTU size is reduced from
>>> 1500 to 1496, somehow...?
>>>
>>> What makes it worse is that hop which drops the MTU does not send ICMP
>>> "packet too long" message back..
>>>
>>> gg# scamper -I "trace -P udp -M abc
>>> traceroute from xxx to abc
>>> 1  s  0.192 ms [mtu: 1500]
>>> 2  d  0.356 ms [mtu: 1500]
>>> *3  f  1.422 ms [mtu: 1500]*
>>> *  4  g  1.107 ms [*mtu: 1496]*
>>>
>>> 5  h  1.145 ms [*mtu: 1496]
>>>
>>>
>>> On the link where MTU drops, output is as follows,
>>>
>>> Protocol inet, MTU: 1500
>>>
>>> Protocol inet6, MTU: 1500
>>>
>>>
>>>
>>> Software version is 10.0R4.7.
>>>
>>>
>>>
>>> Anybody has an experience on this behaviour before.
>>>
>>>
>>>
>>> Thanks and regards,
>>>
>>> Gokhan
>>> ______________________________**_________________
>>> juniper-nsp mailing list juniper-nsp at puck.nether.net
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>>>
>>>
>>
>