Re: MTU to CDN's

[Olivier Benghozi <olivier.benghozi () wifirst fr>]

And also:

When the router generates the ICMP by punting the packet to its CPU and such traffic is - legitimately - rate-limited 
to avoir crashing the router.

When the ICMP is sourced by a private IP on the router for various legitimate reasons (not enough public IPv4 
addresses, from within a VRF, or whatever), while packets from private IPs are legitimately filtered when entering the 
target network.


> Le 19 janv. 2018 à 15:05, Mikael Abrahamsson <swmike () swm pp se> a écrit :
>
> On Fri, 19 Jan 2018, Mike Hammett wrote:
>
> > Other than people improperly blocking ICMP, when does PMTUD not work? Honest question, not troll.
>
> Mismatch of MTU interface settings between interfaces, mismatch of MTU between L3 devices and intermediate L2 
> devices, anycast services, ECMP based services where the ICMP error is delivered to the wrong node.
>
> So yes, there are plenty reasons that PMTUD doesn't work without anyone doing it because of ill will or incompetence.