Anthony R. Gold wrote:
[snip]
>> It's all working now, I hadn't realized that the DNS server had to be
>> changed.
>>
>> I thought that I would only need to change my login details when I changed
>> ISP
>> but I was wrong.
>>
>> Thanks to both.
>>
>> G
>
> I am also surprised you needed to do that. Sounds like BT Broadband may be
> blocking their local resolvers from access from off their network. If you
> use a public resolver such as Google's 8.8.8.8 that should work anywhere,
> and your SIP kit does not depend on having the fastest resolution possible.
I think most domestic ISPs restrict lookup access to their DNS servers
to their own users.
The convention is to configure your router to hand out its own address
as the DNS server, and set up all the client devices to pick up all the
parameter (IP, gateway, DNS) from the router. If you want a client to
have a specific IP address then use the "bind IP to MAC" facility in the
router - not all routers have this, of course.
I see no good reason why a VoIP device should not follow that convention.
However, I have noticed that BT has many DNS servers, not all of which
are available at any one time. Your router will learn about 2 or 3 of
these when it first establishes the PPP session; but later one of this
subset may become unavailable. I have seen no evidence that routers on
BT connections renegotiate their connections when this happens; so
sometimes DNS requests time out and users report that the "internet is
slow". Rebooting the router cures the problem.
So it is normally a good idea to configure the router with a public DNS
resolver, and continue to leave the VoIP device to get its perameters
from the router.
By contrast most other ISPs list only one or two DNS servers (so the
load balancing and failover is done a different way).
--
Graham J