my serevr blocks ping and all access from internet

celsomende · 03-17-2010, 10:02 AM

hi
I have a Centos 5 server working as firewall, dns, proxy (squid) and mail server with postfix. sometimes it blocks ping from the net and when it hapen I cant browse my site not even fetch my email through webmail from outside. But inside every thing still go well even browsing the internet, but no ping to the net (e.g pop.gmail.com). when I restart it everything come up and work fine.
so any body could help please?

thanks

rweaver · 03-17-2010, 01:13 PM

What do you get when you type: iptables -L -n

Tinkster · 03-17-2010, 01:22 PM

How is it connected? If it's intermittent - are you on DSL or
something, or some other home-housed solution?

celsomende · 03-18-2010, 02:02 AM

Quote:

Originally Posted by Tinkster

How is it connected? If it's intermittent - are you on DSL or
something, or some other home-housed solution?

HI
my centos is conect to a cisco router. I've got a leased line to my ISP connected trough cisco router point-to-point. and I got some routeble IP's in my network including this server which is the gateway in the internal network and in it's time the external gateway is the router connected to the ISP.

with iptables -L -n command I got

Chain icmp_packets (1 references)
target prot opt source destination
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 8
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 11

Tinkster · 03-18-2010, 03:42 AM

That's one of the strangest iptables rule sets I've ever seen.
Only ONE chain, pertaining to icmp? Doesn't look right. But
apart from that - did you have a look in the machines logs,
concentrating on time-stamps that (from your knowledge) are
known-bad, i.e., when it refused traffic?

Another thing I'd try (since I've never dealt with a setup
with a leased line) ask my ISP for support, e.g., traffic
snooping or something like that.

Cheers,
Tink