[TriLUG] troubleshooting spotty internet connectivity with TWCBC

[Dewey Hylton]

hi all, just wanting a sanity check here.

i have a customer paying for TWC Business Class service. they run a small shop (~20 computers) behind a *nix firewall, and have been running this basic configuration for over a decade. no interesting changes in the last couple of months. 

friday, they called and said they had issues getting to several external websites that they use daily. i remoted a desktop, looked up the dns record, captured packets on the external interface of the firewall relating to that address, and tried hitting the site with a browser. i saw outbound syn packets, but nothing in return. i duplicated the test for another of their problematic sites and had the same result. plenty of other sites worked fine. they had issues with several sites, but the only two i tested were www.ups.com and mail.yahoo.com.

we've flushed internal dns cache, double-checked dns records against google's cache (8.8.8.8), but stands out to me.

i called TWCBC support. the first tech tried "accessing those 2 sites via the cable modem" and failed. so, believing the problem was on their end, he escalated the ticket. but the second level tech refuses to work with me until i've connected a computer directly to the cable modem. 

does this make sense to anyone? the firewall _is_ a computer, and is much more capable of network testing and such than any of their windows desktops or servers. and it is directly connected to the cable modem already. 

am i missing some bit of logic somewhere?