1)..................................
I hav several clients to this gw.
I want to use IPTABLES for firewall. I downloaded n installed.
iptables comand is working on prompt.

linux> service iptables status
service: no such service iptables

what could be problem???

2)---------------------------

Also if i flush iptables tables to write my own, thn this comp is getting disconnected from LAN

linux> ping 172.31.1.1
PING 172.31.1.1 (172.31.1.1) 56(84) bytes of data.
64 bytes from 172.31.1.1: icmp_seq=1 ttl=63 time=0.517 ms
64 bytes from 172.31.1.1: icmp_seq=2 ttl=63 time=0.501 ms
64 bytes from 172.31.1.1: icmp_seq=3 ttl=63 time=0.504 ms

--- 172.31.1.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.501/0.507/0.517/0.019 ms

linux> iptables -F
linux> ping 172.31.1.1
no response
............................................

1) iptables itself doesn't contain a service. a service is something that is distro specific, so the iptables project in itself can't provide it. an iptables "service" isn't required at all though. the act of "starting" iptables is to apply a set of rules, it doesn't actually run anythign in the background like an apache service or something like that.

2) you've said nothing useful about your topology or ruleset... can't help.

my gw on which this iptables is running is 172.25.2.1
172.31.1.1 is a comp on my network.
172.25.2.22 is client for gw.

my prob here is
if i flush iptables by 'iptables -F' gw is getting off LAN. i.e cant ping 31.1.1

ok ..I wll it put other way.

please tell me how to save iptables rules which i hav added?
Also how to make my rules to get implemented on network restart?( this to avoid writing rules everytime i restart network)