[radvd-devel-l] Changing MTU with radvd (AdvLinkMTU in radvd.conf)

David Shwatrz dshwatrz at gmail.com
Mon Mar 31 04:49:16 EDT 2008

Thanks !
- I did not checked under proc/sys/net...
Running on the host now:
  cat /proc/sys/net/ipv6/conf/eth0/mtu
As expected.
Thanks Again,

On Mon, Mar 31, 2008 at 10:48 AM, Pekka Savola <pekkas at netcore.fi> wrote:
> On Mon, 31 Mar 2008, David Shwatrz wrote:
>  > Any idea why the MTU was not changed from 1500 to 1495 on that host?
>  You're looking at the wrong place.  Neighbor Discovery -derived MTU is
>  updated in a sysctl such as net.ipv6.conf.eth0.mtu -- it isn't
>  reflected in 'ifconfig -a' that (generic) MTU because that affects v4
>  as well.
>  However, if you did tcpdumps of traffic, you should see that v6
>  connections use the lower MTU.  Otherwise the client OS MTU
>  calculation has a bug.
>  I agree that this is not very intuitive place to look for the MTU
>  information but there isn't much I can do about it.. :-)
>  --
>  Pekka Savola                 "You each name yourselves king, yet the
>  Netcore Oy                    kingdom bleeds."
>  Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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