[AusNOG] Upstream PMTUD broken? Packets blackhole

[Cameron Ferdinands]

http://shouldiblockicmp.com/  share with your friends! Great resource

Regards,

On Wed, Sep 14, 2016 at 9:55 AM Mark Newton <newton at atdot.dotat.org> wrote:

> On Sep 14, 2016, at 12:34 AM, s.s.o.n.i.k+a.u.s.n.o.g at gmail.com wrote:
>
> Client firewall MTU set to 1484: Successful reply at length 1456.
> Unsuccessful at 1457, however echo request is seen, and unreachable 3:4
> message is returned by firewall, but never arrives at the source.
>
>
> Ethernet firewall? Why is the MTU so low?
>
> These problems are virtually always caused by a firewall blocking ICMP.
> Usually it’s a firewall operated by the person who is complaining about
> PMTUD not working :-)
>
>   - mark
>
>
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