Re: SBB.ch / IPv6 MTU / fragmentation problem

Jeroen Massar <[email protected]> Tue, 12 Mar 2019 10:58:34 +0100
Newsgroups gmane.org.operators.swinog
Organization Massar
Message-ID <[email protected]>
On 2019-03-12 10:32, Nico Schottelius wrote:
> 
> Good morning,
> 
> is anyone from sbb.ch reading here?
> 
> https://sbb.ch does not load on IPv6 for us.
> It seems that packets > 1420 bytes are dropped inside the SBB network,
> 
> Local PMTU / fragmentation seems to work, my local outgoing
> MTU is 1420. MTR below.

Has been that way for years already.

Long live load balancers & firewalls and people who run them and do not know what they are or how they work.

Don't worry. Google had the same problem for a while and it took them a month or two to realize what the problem was and so did Cloudflare, at least the latter wrote it up so that other people can start getting the problem:

https://blog.cloudflare.com/increasing-ipv6-mtu/

Thus, folks, please read and start fixing your setups... ICMPv6 is required in IPv6 and when you do any kind of load balancing, do honor PTBs...

Greets,
 Jeroen



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