Server is not reachable from one single IP (no iptables-rules nor host.deny)

Question

I have a Debian-Server with IMAP, Apache, and SMTP running.

From one particular IP I have no access to the server -- the server is unavailable, but for other clients it is available!

I can not traceroute from the server to the particular IP:

traceroute to 88.209.67.xx (88.209.67.xx), 30 hops max, 60 byte packets
 1  server.com (88.198.57.xx)  3005.394 ms !H  3005.391 ms !H  3005.387 ms !H

...and tracerouting from that IP to the server ends on the last hop but one (Juniper Switch in Data-Center).

Please advise on how to solve the issue. No iptable rules or hosts-deny block are in effect for this IP. There is no output from: grep -R IPADRESS /var/log and in /etc/

Answer 1

Perhaps there's a routing problem at the Juniper switch? If someone else is responsible for that switch, ask them if they've been experiencing some routing issues lately and mention your problem to them where only your particular IP can't reach it.

I wonder if there could even be some rare ARP caching problems, which I've seen from time-to-time with big ISPs -- clearing the ARP cache can solve a lot of problems if they're not clearing up on their own over time.