AT&T internet and dns with vpn

[high_revs]

trying to help one of my colleagues. person moved and now has at&t as internet provider. has same laptop, and same vpn to our work data centers. once in at&t, vpn works but cannot get to all servers in our data center (to ssh for example). some work; some don't. me and another person thought it's the dns of at&t so recommendation to change to, say, google dns. but that shouldn't be a solution since once vpn'ed in, it's the internal network that's the issue. anyway, using google dns didn't solve it.

i didn't know at&t has to use proprietary equipment. i offered my old docsis 2.0 to isolate issue with at&t combined modem/router. but at&t doesn't use docsis 2 as i was told. internal network person helping (unofficially since different dept) thinks it's a config file. doesn't make sense to me and other colleague since all that changed is internet provider. no issues vpn'ing to data center in work (we don't have direct line to data center; have to vpn still).

by chance is it the router portion of at&t? person needs to get a at&t sanctioned router? if that doesn't work, that'll suck.

thoughts? my internet kung fu couldn't find anything but this is really a niche type problem most consumers won't know/go thru.

p.s. person can get to servers via ip# but has to do nslookup.

[yellowsulphur]

Are the unreachable servers using the standard ports for the services they provide? If so, maybe add entries into to the host file until you can find a real solution.

https://support.rackspace.com/how-to/modify-your-hosts-file/

[stonith3901]

When your VPN is initiated, they should push DNS servers provided by the VPN server so you as a VPN user can resolve internal DNS. The VPN server also gives you an ip address that is attached to a client virtual ethernet adapter. You should not be using your external DNS provided servers. Also the VPN server should be pushing internal subnet routes so that your VPN client knows that those set of ip addresses are related to work go over your client virtual ethernet adapter. The VPN server can over ride your default gateway and push all traffic over the VPN tunnel or it can be split tunnel where only work related stuff goes over the VPN tunnel.

[stonith3901]

Ok more I think about it. It seems like your friend had it working at one point but when using a new ISP (moved) some stuff isnt working. It sounds like your friend is experiencing a network collision. He might be using a subnet at his source that is the same as work and is causing confusion. Again your VPN server should be providing and pushing DNS servers amd overriding the ones provided by your source networks. You guys should do troubleshooting with your network engineer that configured the VPN server.

[FresnoRob]

Ok more I think about it. It seems like your friend had it working at one point but when using a new ISP (moved) some stuff isnt working. It sounds like your friend is experiencing a network collision. He might be using a subnet at his source that is the same as work and is causing confusion. Again your VPN server should be providing and pushing DNS servers amd overriding the ones provided by your source networks.You guys should do troubleshooting with your network engineer that configured the VPN server.

This is the first thing I thought of after reading the OP post.

[high_revs]

Thanks for feedback. we'll look more at the collision thing.

it is strange that direct ip# works but not the host name.