IPTables: Difference between revisions
From Leo's Notes
This page was last edited on 10 March 2015, at 17:18.
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iptables -t nat -A OUTPUT -p udp -d 1.2.3.4 --dport 443 -j DNAT --to-destination 9.8.7.6:8080 | iptables -t nat -A OUTPUT -p udp -d 1.2.3.4 --dport 443 -j DNAT --to-destination 9.8.7.6:8080 | ||
== Delete a Specific Rule in a Chain == | |||
Suppose I have the following chain and rules: | |||
<syntaxhighlight lang="text"> | |||
# iptables -t nat -L neutron-l3-agent-snat -n | |||
Chain neutron-l3-agent-snat (1 references) | |||
target prot opt source destination | |||
neutron-l3-agent-float-snat all -- 0.0.0.0/0 0.0.0.0/0 | |||
SNAT all -- 172.20.20.0/24 0.0.0.0/0 to:136.159.2.206 | |||
SNAT all -- 136.159.4.0/24 0.0.0.0/0 to:136.159.2.206 | |||
</syntaxhighlight> | |||
To delete a specific rule, it's easiest to define which line to delete. | |||
<syntaxhighlight lang="text"> | |||
# iptables -t nat -L neutron-l3-agent-snat -n --line-number | |||
Chain neutron-l3-agent-snat (1 references) | |||
num target prot opt source destination | |||
1 neutron-l3-agent-float-snat all -- 0.0.0.0/0 0.0.0.0/0 | |||
2 SNAT all -- 172.20.20.0/24 0.0.0.0/0 to:136.159.2.206 | |||
3 SNAT all -- 136.159.4.0/24 0.0.0.0/0 to:136.159.2.206 | |||
</syntaxhighlight> | |||
Then delete it using the line number: | |||
# iptables -t nat -D neutron-l3-agent-snat 3 | |||
[[Category:Linux]] | [[Category:Linux]] | ||
[[Category:IPTables]] | [[Category:IPTables]] | ||
Revision as of 17:18, 10 March 2015
Prerouting Chain
This is the first chain that traffic will go through. It contains the following tables:
- raw
- connection tracking
- mangle
- destination / NAT
Drop RFC3330
You may wish to drop Special-Use IP addresses defined in RFC 3330. These IPs include internally routed addresses such as 192.168.0.0/16, 10.0.0.0/8, etc., black-hole addresses such as 0.0.0.0, and multicast addresses such as 224.0.0.0/4. There should be no reason for these addresses to be coming in externally and when it does happen, it's probably a spoofed address.
# # DROP RFC3330 # $IPT -t mangle -A PREROUTING -s 0.0.0.0/8 -j DROP -m comment --comment "0.0.0.0/8 source" $IPT -t mangle -A PREROUTING -d 0.0.0.0/8 -j DROP -m comment --comment "0.0.0.0/8 destination" $IPT -t mangle -A PREROUTING -s 10.0.0.0/8 -j DROP -m comment --comment "10.0.0.0/8 source" $IPT -t mangle -A PREROUTING -d 10.0.0.0/8 -j DROP -m comment --comment "10.0.0.0/8 destination" $IPT -t mangle -A PREROUTING -s 100.64.0.0/10 -j DROP -m comment --comment "100.64.0.0/10 source" $IPT -t mangle -A PREROUTING -d 100.64.0.0/10 -j DROP -m comment --comment "100.64.0.0/10 destination" $IPT -t mangle -A PREROUTING -s 169.254.0.0/16 -j DROP -m comment --comment "169.254.0.0/16 source" $IPT -t mangle -A PREROUTING -d 169.254.0.0/16 -j DROP -m comment --comment "169.254.0.0/16 destination" $IPT -t mangle -A PREROUTING -s 172.16.0.0/12 -j DROP -m comment --comment "172.16.0.0/12" $IPT -t mangle -A PREROUTING -d 172.16.0.0/12 -j DROP -m comment --comment "172.16.0.0/12" $IPT -t mangle -A PREROUTING -s 192.0.2.0/24 -j DROP -m comment --comment "192.0.2.0/24 source" $IPT -t mangle -A PREROUTING -d 192.0.2.0/24 -j DROP -m comment --comment "192.0.2.0/24 destination" $IPT -t mangle -A PREROUTING -s 192.168.0.0/16 -j DROP -m comment --comment "192.168.0.0/16 source" $IPT -t mangle -A PREROUTING -d 192.168.0.0/16 -j DROP -m comment --comment "192.168.0.0/16 destination" $IPT -t mangle -A PREROUTING -s 198.18.0.0/15 -j DROP -m comment --comment "198.18.0.0/15 source" $IPT -t mangle -A PREROUTING -d 198.18.0.0/15 -j DROP -m comment --comment "198.18.0.0/15 destination" $IPT -t mangle -A PREROUTING -s 198.51.100.0/24 -j DROP -m comment --comment "198.51.100.0/24 source" $IPT -t mangle -A PREROUTING -d 198.51.100.0/24 -j DROP -m comment --comment "198.51.100.0/24 destination" $IPT -t mangle -A PREROUTING -s 203.0.113.0/24 -j DROP -m comment --comment "203.0.113.0/24 source" $IPT -t mangle -A PREROUTING -d 203.0.113.0/24 -j DROP -m comment --comment "203.0.113.0/24 destination" # Special usue IPs, including 255.255.255.255. $IPT -t mangle -A PREROUTING -s 240.0.0.0/4 -j DROP -m comment --comment "240.0.0.0/4 source" $IPT -t mangle -A PREROUTING -d 240.0.0.0/4 -j DROP -m comment --comment "240.0.0.0/4 destination" # We shouldn't be routing multicast. $IPT -t mangle -A PREROUTING -s 244.0.0.0/4 -j DROP -m comment --comment "244.0.0.0/4 source" $IPT -t mangle -A PREROUTING -d 244.0.0.0/4 -j DROP -m comment --comment "244.0.0.0/4 destination" # Loopback not allowed unless on the local loopback interface. $IPT -t mangle -A PREROUTING -s 127.0.0.0/8 ! -i lo -j DROP -m comment --comment "127.0.0.0/8 source, DROP except on the loopback" $IPT -t mangle -A PREROUTING -d 127.0.0.0/8 ! -i lo -j DROP -m comment --comment "127.0.0.0/8 destination, DROP except on the loopback"
Redirect Outgoing Traffic to Local Port
To redirect traffic destined to 1.2.3.4:443 to localhost:8080, use the REDIRECT directive:
iptables -t nat -A OUTPUT -p tcp -d 1.2.3.4 --dport 443 -j REDIRECT --to-ports 8080
If you want to redirect traffic to a particular destination rather than 127.0.0.1 (or the primary interface's IP) use DNAT:
iptables -t nat -A OUTPUT -p udp -d 1.2.3.4 --dport 443 -j DNAT --to-destination 9.8.7.6:8080
Delete a Specific Rule in a Chain
Suppose I have the following chain and rules:
# iptables -t nat -L neutron-l3-agent-snat -n
Chain neutron-l3-agent-snat (1 references)
target prot opt source destination
neutron-l3-agent-float-snat all -- 0.0.0.0/0 0.0.0.0/0
SNAT all -- 172.20.20.0/24 0.0.0.0/0 to:136.159.2.206
SNAT all -- 136.159.4.0/24 0.0.0.0/0 to:136.159.2.206
To delete a specific rule, it's easiest to define which line to delete.
# iptables -t nat -L neutron-l3-agent-snat -n --line-number
Chain neutron-l3-agent-snat (1 references)
num target prot opt source destination
1 neutron-l3-agent-float-snat all -- 0.0.0.0/0 0.0.0.0/0
2 SNAT all -- 172.20.20.0/24 0.0.0.0/0 to:136.159.2.206
3 SNAT all -- 136.159.4.0/24 0.0.0.0/0 to:136.159.2.206
Then delete it using the line number:
# iptables -t nat -D neutron-l3-agent-snat 3