DNS Question, work related

ande0255

Heya, aside from a bit of labbing for the VCP I am very unfamiliar with DNS. I have a site of about 15 people who are unable to get to their company website internally, but off their network there is no issue loading the website, and even the DC that is doing DNS for them is able to load their company website (and it's on the same subnet as users).

I've had them flush dns, restarted dns services on the DC, and they are still unable to get to their company website but can hit all other websites (google, yahoo, etc). I did also verify the users are getting the DC as their DNS server, can ping the DNS server by both IP addy and machine name, I just don't know what else to try.

Any ideas?

tstrip007

their website is hosted on their own webserver and the webserver is on the same subnet as the users? I've had issues in the past with the gateway disappearing leaving folks on other subnets not able to access. By no means a perm solution but you could add the webserver ip to the users host file until a perm solution is establised.

ande0255

Its hosted by the company webfaction.com I believe. So I found that all users pc's are getting out of the gateway via dynamic NAT (overload), so they are all hitting the host site from the same public IP, whereas the DC has a static NAT setup that it would be hitting the site from.

I also used ASDM and watched the users address hit the internal DNS and send TCP requests out the firewall to the correct IP, but it kept tearing down / trying to re-establish the connection, so I am thinking that perhaps the main public IP for users got put on a blacklist or something similar for the hosting company.

Either way I think I proved it is not internal DNS or the firewall, though the dynamic NAT having issues but static NAT'd host being all good remains suspicious to me.

lmoworld

- bypass proxy for local address check box is checked
- try accessing site by ip
- re-install browser
- Are users authenticated for access if so (check certificates)

Warning: I am not a SME. Just making guesses

life980

One of the things to keep in mind is that routers prevent loop back traffic. So that's why corporate DNS works by providing internal IP address of web server when within internal network and external for the general internet.

The loop back traffic restriction can be removed from certain routers but it certainly seems like a router or firewall issue.

jonny72

ande0255 wrote: »

I also used ASDM and watched the users address hit the internal DNS and send TCP requests out the firewall to the correct IP, but it kept tearing down / trying to re-establish the connection, so I am thinking that perhaps the main public IP for users got put on a blacklist or something similar for the hosting company.

Check with the web host, or via the hosting control panel if you have access, to see if the public IP is blocked. I've seen this happen before, never figured out why it happened but I suspect something inside the internal network was flooding the website with requests or sending dodgy requests.

The most common cause I've seen of this is split DNS, with the internal DNS being wrong - but it looks like you've ruled this out.