[j-nsp] IPv6 MTU issue

[Alex]

It should, in my view.
Rgds
Alex
  ----- Original Message ----- 
  From: Gökhan Gümüs 
  To: Alex 
  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

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