CentOS5.0でIPマスカレード

2007年10月31日 04:51

Linuxサーバでインターネットに繋げるので、プライベートLAN上のPCからインターネットに出て行くパケットをIPマスカレードしなければいけない。

[root@ml115 ~]# iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
[root@ml115 ~]# iptables -A RH-Firewall-1-INPUT -i eth0 -j ACCEPT
[root@ml115 ~]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere

Chain FORWARD (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Chain RH-Firewall-1-INPUT (2 references)
target prot opt source destination
ACCEPT all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere icmp any
ACCEPT esp -- anywhere anywhere
ACCEPT ah -- anywhere anywhere
ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns
ACCEPT udp -- anywhere anywhere udp dpt:ipp
ACCEPT tcp -- anywhere anywhere tcp dpt:ipp
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
ACCEPT all -- anywhere anywhere
[root@ml115 ~]#
[root@ml115 ~]# service iptables save
Saving firewall rules to /etc/sysconfig/iptables: [ OK ]
[root@ml115 ~]#
[root@ml115 ~]# cat /etc/sysconfig/iptables
# Generated by iptables-save v1.3.5 on Mon Oct 29 04:52:14 2007
*nat
:PREROUTING ACCEPT [641:202508]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [1:70]
-A POSTROUTING -o ppp0 -j MASQUERADE
COMMIT
# Completed on Mon Oct 29 04:52:14 2007
# Generated by iptables-save v1.3.5 on Mon Oct 29 04:52:14 2007
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [718:77534]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp -m icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p esp -j ACCEPT
-A RH-Firewall-1-INPUT -p ah -j ACCEPT
-A RH-Firewall-1-INPUT -d 224.0.0.251 -p udp -m udp --dport 5353 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 10022 -j ACCEPT
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
-A RH-Firewall-1-INPUT -i eth0 -j ACCEPT
COMMIT
# Completed on Mon Oct 29 04:52:14 2007
[root@ml115 ~]#

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