Date: Tue, 24 Jun 2014 19:52:05 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Andrea Venturoli <ml@netfence.it> Cc: freebsd-net@freebsd.org Subject: Re: MTU not regrowing? Message-ID: <20140625025205.GR1560@funkthat.com> In-Reply-To: <53A9C6D0.3090900@netfence.it> References: <53A9C6D0.3090900@netfence.it>
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Andrea Venturoli wrote this message on Tue, Jun 24, 2014 at 20:43 +0200:
> Today I experienced something weird (at least for me) on a 8.4 system:
>
> _ the system had vlan3 interface, with default MTU (1500 bytes);
> _ "ping -D -s 1400 somehost" would work, but "ping -D -s 1500 somehost"
> would yield "frag needed and DF set" (forgive me if the message is not
> exact, I don't have it anymore);
>
> _ to make some tests I reduced MTU size with "ifconfig vlan3 mtu 500";
> _ now, of course, "ping -D -s 400 somehost" would work, but "ping -D -s
> 500 somehost" would yield "frag needed and DF set";
>
> _ then I raised MTU again with "ifconfig vlan3 mtu 1500" (notice
> ifconfig would actually report this as "mtu 1500" was shown);
> _ however the results were as before, i.e. "ping -D -s 400 somehost"
> would work, but "ping -D -s 500 somehost" would yield "frag needed and
> DF set";
>
> _ no way I could ping with a packet bigger than 500 bytes until I rebooted.
>
> Is this expected behaviour? Any way to get around this?
This is expected behavior.. You need to delete the network route
as that stores the MTU that is cloned to the host routes... HEAD
and I believe 10 doesn't have this issue..
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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