I have 2 internet connections from 2 different ISPs with static IPs, lets call them A and B. A connects to the server in several ways (ping, SSH, HTTP), while B cannot do anything (ping, SSH, HTTP).
I ran tcpdump on the server using connection A, and then tried to call a webpage using B. It appears that B has reached the server, so that rules out that the problem is from ISP B.
I checked the iptables but there is nothing that bans B ip! I checked hosts.deny file as well but there is nothing in it too.
What might be the problem? Is there any more tests that would help in reaching to the problem source?