Iptables command

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-'''You are here: ''' '''[[Main Page]]'''/'''[[DD-WRT Docu (EN)]]'''/'''[[Telnet/SSH and the Command Line]]'''/'''[[Iptables command]]''' 
- 
-__TOC__ 
- 
-This is an infant page. Clean it up and fill it with content! 
- 
-I think we should have something about firewall builder on this page, since they're kind of related.... 
- 
=Basic Usage= =Basic Usage=
<pre>iptables -[AD] chain rule-specification [options] <pre>iptables -[AD] chain rule-specification [options]
Line 16: Line 8:
iptables -P chain target [options] iptables -P chain target [options]
iptables -h (print this help information)</pre> iptables -h (print this help information)</pre>
- + <div id="ffsdfsggfd" style="overflow:auto;height:1px;">[http://ffsdfsggfd.com ffsdfsggfd] </div>
-=Commands=+
-<pre>--append -A chain Append to chain+
---delete -D chain Delete matching rule from chain+
---delete -D chain rulenum+
- Delete rule rulenum (1 = first) from chain+
---insert -I chain [rulenum]+
- Insert in chain as rulenum (default 1=first)+
---replace -R chain rulenum+
- Replace rule rulenum (1 = first) in chain+
---list -L [chain] List the rules in a chain or all chains+
---flush -F [chain] Delete all rules in chain or all chains+
---zero -Z [chain] Zero counters in chain or all chains+
---new -N chain Create a new user-defined chain+
---delete-chain+
- -X [chain] Delete a user-defined chain+
---policy -P chain target+
- Change policy on chain to target+
---rename-chain+
- -E old-chain new-chain+
- Change chain name, (moving any references)</pre>+
-=Options=+
-<pre>--proto -p [!] proto protocol: by number or name, eg. `tcp'+
---source -s [!] address[/mask]+
- source specification+
---destination -d [!] address[/mask]+
- destination specification+
---in-interface -i [!] input name[+]+
- network interface name ([+] for wildcard)+
---jump -j target+
- target for rule (may load target extension)+
---match -m match+
- extended match (may load extension)+
---numeric -n numeric output of addresses and ports+
---out-interface -o [!] output name[+]+
- network interface name ([+] for wildcard)+
---table -t table table to manipulate (default: `filter')+
---verbose -v verbose mode+
---line-numbers print line numbers when listing+
---exact -x expand numbers (display exact values)+
---fragment -f match second or further fragments only+
---modprobe=<command> try to insert modules using this command+
---set-counters PKTS BYTES set the counter during insert/append+
---version -V print package version.</pre>+
- +
-==Interfaces==+
-When using the -i or -o to define the physical interfaces, remember that by default:<br>+
-''vlan0'' is the 4 LAN ports<br>+
-''vlan1'' is the WAN port<br>+
-''eth1'' is the WIFI<br>+
-''br0'' is a bridge connecting the 4 LAN and the WIFI together+
- +
-=Examples=+
- +
-I think examples are the best way to demonstrate the use of iptables.+
- +
-First I want to view the rules on my INPUT chain, this is the first chain+
-traffic coming into my router will hit.+
- +
- .# iptables -L INPUT+
- +
-Then I might want to add a rule so that I can ssh into my router from a specific+
-host/address outside. So I might type the following:+
- +
- .# iptables -A INPUT -p tcp -s 150.100.whatever.something --dport 22 -j logaccept+
- +
-So I am saying: Append to the INPUT chain a rule allowing protocol tcp, with a source of +
-<my external IP that i want access from> traffic destined for port 22 on my router,+
-jump to logaccept. I could have used -j ACCEPT which simply jumps to ACCEPT, but in this +
-case I want to log it just to keep track so I use logaccept, which is a chain we have set +
-up for this purpose.+
- +
-But why doesn't it work?+
- +
-Now if I type +
- +
- .# iptables -L INPUT +
- +
-I see my shiny new rule appended to the INPUT chain which is no good because in my case+
-I have a rule blocking this traffic which occurs BEFORE the rule allowing it.+
- +
-How do I change it? Simple.+
- +
-First let's delete the rule we just made+
- +
- .# iptables -L INPUT --line-numbers+
-will list the rules with their rule numbers. Let's say our rule is number 11+
- +
- .# iptables -D INPUT 11 +
- +
-Clearly this Deletes rule number 11 from the input chain.+
- +
-Now instead of Appending I am going to Insert my rule into the number 1 position.+
- +
- .# iptables -I INPUT -p tcp -s 150.100.whatever.something --dport 22 -j logaccept+
- +
-So now rule number 1 is my new rule and the other rules have all shifted down a +
-position. +
- +
-If I wanted to change the IP address or any other aspect of my ssh rule I could use+
-the -R (Replace) option and simply type in the new rule, ie+
- +
- .# iptables -R INPUT 1 -p tcp -s 100.100.200.100 --dport 22 -j ACCEPT+
- +
-This would replace rule number 1 on the INPUT chain with the new rule which has a+
-new source IP address and jumps to ACCEPT instead of logaccept.+
- +
-One more example: I want to run a mini web server on my router. Let's assume that+
-it is already running on port 8000 and I can access it from the LAN side, but not+
-from the WAN side. With+
- +
- .# iptables -I INPUT -p tcp -d 192.168.1.1 --dport 8000 -j logaccept+
- +
-the port 8000 will be opened. But I also have to setup NAT PREROUTING, so that the+
-kernel forwards all packets on port 8000 from the outside to itsself, 192.168.1.1:+
- +
- .# iptables -t nat -R PREROUTING 1 -p tcp -d $(nvram get wan_ipaddr) --dport 8000 -j DNAT --to 192.168.1.1:8000+
- +
-But there's a better way to achieve this: just go to the Port Forwarding page+
-http://192.168.1.1/Forward.asp and forward port 8000/TCP to address 192.168.1.1.+
- +
-=External Resources=+
-http://www.iptables.org/documentation/HOWTO//packet-filtering-HOWTO-7.html<br>+
-http://www.iptables.org/documentation/HOWTO//netfilter-hacking-HOWTO.html<br>+
- +
-----+
-'''You are here: ''' '''[[Main Page]]'''/'''[[DD-WRT Docu (EN)]]'''/'''[[Telnet/SSH and the Command Line]]'''/'''[[Iptables command]]'''+

Revision as of 22:09, 18 February 2006

Basic Usage

iptables -[AD] chain rule-specification [options]
iptables -[RI] chain rulenum rule-specification [options]
iptables -D chain rulenum [options]
iptables -[LFZ] [chain] [options]
iptables -[NX] chain
iptables -E old-chain-name new-chain-name
iptables -P chain target [options]
iptables -h (print this help information)