firewall problems

[realpv]

Hi All
my machine is not pinging from outside
i have machine A behind firewall b
when i try to ping machine A from internet (machine C)
i get a output like this in /var/log/messages

Jan 6 05:58:20 firewall kernel: IN=eth0 OUT=eth2 SRC=15.x1.x2.30 DST=22.y.x.22 LEN=84 TOS=0x00 PREC=0x00 TTL=45 ID=181 PROTO=ICMP TYPE=8 CODE=0 ID=26628 SEQ=0

so it's not pinging machine A.

But from machine A it's pinging machine C...


so what's the problem

waiting for ur reply
prashant

[Aaron_Adams]

It is possible that the firewall is configured to ACCEPT outgoing ICMP Echo packets and incoming ICMP Echo Reply packets, but is configured to DROP incoming ICMP Echo packets. Thus allowing a machine to respond to your ping request, but not allowing an outside machine to ping you.

Are you able to ping your firewall at all?

[ediks]

I thinks that when you ping someone you establish a state that allows that connection to send stuff back through your firewall. So if you have something like this

iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

And you ping someone, than a state gets established and they can send you stuff back. If they decide to ping you the firewall will block it.

[friskydrifter]

Does machine A have a 'real address" ?

if it is masqueraded behind the firewall i'd wonder how you are going to ping it ?