I use m0n0wall as a filtering bridge. A DNS server is behind it. While I use
this DNS from inside my internal network, I can browse with internet
explorer www.symantec.com because the resolved packets don't go through
m0n0wall. But if I am outside my network, I can't browse Symantec.
I thought it was a virus, but guess what, by changing the DNS server to some
other I was able to browse Symantec's website. Strange.
So I googled a bit and found this:
It ends saying
: You have a firewall blocking the EDNS responses > 512 octets.
: Contact your firewall vendor for an upgrade.