I have hosta
and hostb
, two dedicated server in the same area (same bay?).
Ping and communication towards these hosts are okay. But hosta
seems to have all its outgoing communications on port 25 blocked somehow:
With nc working-smtp 25
(and and port 80
) on both hosts. I figured that:
hosta
has all it's outgoing communication timeouted on port25
only.hostb
work fine.
Note that working-smtp
is a working smtp server unrelated to both of them, practical to make test (and where I have put a tcpdump
to double check connections.)
BTW, both hosts can ping working-smtp
.
So I did a traceroute -p 25 -T working-smtp
, and first two server in both traceroute are EXACTLY the same:
# traceroute -p 25 -T working-server
traceroute to working-server (xx.xx.xx.xx), 30 hops max, 60 byte packets
1 A (xx.xx.xx.xx) 0.363 ms * *
2 B (xx.xx.xx.xx) 0.819 ms 1.063 ms 1.166 ms
...
(A and B are network gateways out of my control from the dedicated bay.)
- On
hosta
, the next hops are* * *
until it reaches max hop number. - On
hostb
, the next hops are all valued and it reachesworking-server
in 6 hops.
If I do the same traceroute
with port 80, both server reaches the target with the same track.
What conclusion could we draw ? Is there more test to do ? Should I contact my dedicated server provider ?
hosta
to port 25 on a known working smtp server, and getting only as far as network gateway B. Are you able to ping the smtp server fromhosta
? It seems reasonable to me to contact the service provider.ping
, andtraceroute
on port80
are all working like a charm. Some UDP packet reachesworking-server
if I do atraceroute -U
(but its output strangely is similar to the one on failing TCP 25). So, this failure hits only outgoing TCP communication on port 25.hosta
- it sounds like you might.hosta
, I have checked shorewall, and I did a 'iptables | grep 25' (a bit rough, but since it didn't give anything...).