Bind - OPT UDPsize=1232 ?

[Karl Pielorz]

--On 1 June 2021 at 13:03:12 +0200 Anand Buddhdev <anandb at ripe.net> wrote:

> On 01/06/2021 12:55, Karl Pielorz wrote:
>
> Hi Karl,
>
>> Anyone know why the Bind query appears to set such a low UDPsize? -
>> We've nothing in our config setting sizes, or maximums.
>
> Here's an answer:
>
> https://bind9.readthedocs.io/en/v9_16_16/notes.html#notes-for-bind-9-16-16
>
> Regards,
> Anand

Hi,

Thanks for the pointer - ok, yes I can see it's probably EDNS / Flag day 
related etc. I missed that - probably as it's never caused us an issue. 
Annoyingly a value of 1232 causes a TCP fallback to a server out of our 
control that doesn't do TCP very well.

Even more annoyingly - all the 'flag day' / online test sites we can find - 
it works with, and passes all the tests.

Which means even if there were a chance of getting the remote server fixed 
it's going to get "well, it works everywhere else and the online tests say 
it's a pass..."

Thanks again though,

-Karl