BIND and UDP tuning

[G.W. Haywood]

Hello again,

On Mon, 1 Oct 2018, Alex wrote:

> > Are your requests being dropped by the service(s)?
> >
> > (Or: are you inadvertently abusing the said service(s)?)
> 
> I don't believe so - often times a follow-up host query succeeds
> without issue. It's also failing for invaluement and spamhaus, both
> of which we subscribe.
> [...]
> It also tends to happen in bulk - there may be 25 SERVFAILs within
> the same second, then nothing for another few minutes.

Hmmm.  If it isn't the modem and it isn't the BLs then it more or less
has to be the service, no?

I'd be tempted by Mr. Clegg's suggestion to spin up a VPS somewhere
with decent connection, which will at least offload a lot of retries.
Talk to it through OpenVPN, which is very easy to set up, and it can
(a) put the VPS on your LAN (b) take much unreliablility out of the
presumably unreliable connection between you and the VPS and (c) write
very verbose logs if you wish.  On occasion on unreliable connections
I've had to use TCP for the VPN link but UDP is the norm - OpenVPN has
its own ways of dealing with lost packets.

Then you'll probably have a whole new can of worms to investigate, but
the worms will definitely tell you something. :)

-- 

73,
Ged.