Broadband problem...don't know if it's software or ISP DNS issues 2

[DanielUK]

Hi,

Our whole network (win 2k DC with handful of win2k clients) has suddenly stopped being able to browse http pages. Ping, email and https pages work fine. I've plugged in an exact match and configured router (Netgear DG384) and get the same problem so I know it's not the router hardware.

The router admin says it is connected but can't browse directly to web on it's own test (which at this point is not reliant on any network server settings).

However, when I unplug the broadband router and plug in our backup Cisco ISDN router which uses a different ISP, everything works fine. This tells me it's not some firewall setting blocking port 80 as I've seen in other posts.

My broadband ISP are investigating (BT Broadband) but I'm trying to work out if it is anything our end.

I've checked the ip addresses of the ISP DNS Servers in the forwarders tab of the DC running internal DNS and it is all correct. Nothing has changed, it just suddenly happened.

My gut feeling is it is BT that have the problem, based on all of the above factors but not sure where to go next other than wait!?

Thanks

Dan

 

[dearingkr]

OK, first of all, I assume you have your internal DNS set up correctly:
1. All client PC's and servers configured to use internal DNS server.
2. Internal DNS server configured to use localhost for DNS
3. Internal DNS server forwarders configured to use ISP DNS servers.

Next, bypass the internal DNS server.
Temporarily re-configure one of the client PCs with a static IP, subnet, degault gateway, and with the ISP's DNS

Does it work?
If yes, then you have an issue with your server.
If no, then the problem is either your router/firewall or the ISP.
If you suspect the SIP, I would call BT and ask them for a different DNS IP you can use for testing, they're a big enough company that I'm sure they have more than what you know of.

MCSE CCNA CCDA

 

[DanielUK]

Thanks dearingkr,

I was about to trouble shoot this some more with your suggestions when it all started working again! I did nothing, so suspect BT was the problem but the advice you've given about bypassing the DNS server is handy for the future.

Thankyou,

Dan