这里将载有Openwrt的WR841N的路由表dump出来分析一下。

这个是dump出iptables的命令

root@OpenWrt:/etc/config# iptables-save

这里分为4部分：

1.NAT表

*nat
:PREROUTING ACCEPT [37930:3638072]
:INPUT ACCEPT [440:34479]
:OUTPUT ACCEPT [1004:101848]
:POSTROUTING ACCEPT [149:36868]
:MINIUPNPD - [0:0]
:delegate_postrouting - [0:0]
:delegate_prerouting - [0:0]
:postrouting_lan_rule - [0:0]
:postrouting_rule - [0:0]
:postrouting_wan_rule - [0:0]
:prerouting_lan_rule - [0:0]
:prerouting_rule - [0:0]
:prerouting_wan_rule - [0:0]
:zone_lan_postrouting - [0:0]
:zone_lan_prerouting - [0:0]
:zone_wan_postrouting - [0:0]
:zone_wan_prerouting - [0:0]
-A PREROUTING -j delegate_prerouting 
-A POSTROUTING -j delegate_postrouting 
-A delegate_postrouting -m comment --comment "user chain for postrouting" -j postrouting_rule 
-A delegate_postrouting -o br-lan -j zone_lan_postrouting 
-A delegate_postrouting -o eth0 -j zone_wan_postrouting 
-A delegate_postrouting -o pppoe-wan -j zone_wan_postrouting 
-A delegate_prerouting -m comment --comment "user chain for prerouting" -j prerouting_rule 
-A delegate_prerouting -i br-lan -j zone_lan_prerouting 
-A delegate_prerouting -i eth0 -j zone_wan_prerouting 
-A delegate_prerouting -i pppoe-wan -j zone_wan_prerouting 
-A zone_lan_postrouting -m comment --comment "user chain for postrouting" -j postrouting_lan_rule 
-A zone_lan_prerouting -m comment --comment "user chain for prerouting" -j prerouting_lan_rule 
-A zone_wan_postrouting -m comment --comment "user chain for postrouting" -j postrouting_wan_rule 
-A zone_wan_postrouting -j MASQUERADE 
-A zone_wan_prerouting -j MINIUPNPD 
-A zone_wan_prerouting -m comment --comment "user chain for prerouting" -j prerouting_wan_rule 
COMMIT

其中方括号里面的数据是当前所使用的流量（数据包数和byte数）。

总结为下图：

其中从LAN口流入的流量递交给了miniupnpd处理，这个工具有益于P2P下载。

往WAN口去的流量使用了MASQUERADE，是SNAT的增强型，可以转换源IP地址，这样的话就可以发挥路由器的NAT功能了，同时

支持多个客户端。

2.RAW表

*raw
:PREROUTING ACCEPT [3358190:2718603756]
:OUTPUT ACCEPT [14202:1858213]
:notrack - [0:0]
-A PREROUTING -j notrack 
COMMIT

这里基本上没有做什么，不进行分析

3.MANGLE表

*mangle
:PREROUTING ACCEPT [3358190:2718603756]
:INPUT ACCEPT [14538:1853317]
:FORWARD ACCEPT [3342456:2716312729]
:OUTPUT ACCEPT [14202:1858213]
:POSTROUTING ACCEPT [3356900:2718229627]
:ASSIGNOUT - [0:0]
:NWANOUT - [0:0]
:NWANPOS - [0:0]
:NWANPRE - [0:0]
:fwmark - [0:0]
:mssfix - [0:0]
-A PREROUTING -j ASSIGNOUT 
-A PREROUTING -j NWANPRE 
-A PREROUTING -j fwmark 
-A FORWARD -j mssfix 
-A OUTPUT -j NWANOUT 
-A POSTROUTING -j NWANPOS 
-A ASSIGNOUT -m state --state RELATED,ESTABLISHED -j RETURN 
-A NWANOUT -m conntrack --ctstate RELATED,ESTABLISHED -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff 
-A NWANPOS -o pppoe-wan -m state --state NEW -j CONNMARK --set-xmark 0xa/0xffffffff 
-A NWANPRE -i pppoe-wan -m state --state NEW -j CONNMARK --set-xmark 0xa/0xffffffff 
-A NWANPRE -i br-lan -m conntrack --ctstate RELATED,ESTABLISHED -j CONNMARK --restore-mark --nfmask 0xffffffff --ctmask 0xffffffff 
-A mssfix -o eth0 -p tcp -m tcp --tcp-flags SYN,RST SYN -m comment --comment "wan (mtu_fix)" -j TCPMSS --clamp-mss-to-pmtu 
-A mssfix -o pppoe-wan -p tcp -m tcp --tcp-flags SYN,RST SYN -m comment --comment "wan (mtu_fix)" -j TCPMSS --clamp-mss-to-pmtu 
COMMIT

这里在prerouting，output和postrouting的时候做了CONNMRK，用于连接管理，比如做QOS管理。在转发的时候修改了MSS。

4.FILTER表

*filter
:INPUT ACCEPT [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
:MINIUPNPD - [0:0]
:delegate_forward - [0:0]
:delegate_input - [0:0]
:delegate_output - [0:0]
:forwarding_lan_rule - [0:0]
:forwarding_rule - [0:0]
:forwarding_wan_rule - [0:0]
:input_lan_rule - [0:0]
:input_rule - [0:0]
:input_wan_rule - [0:0]
:output_lan_rule - [0:0]
:output_rule - [0:0]
:output_wan_rule - [0:0]
:reject - [0:0]
:syn_flood - [0:0]
:zone_lan_dest_ACCEPT - [0:0]
:zone_lan_forward - [0:0]
:zone_lan_input - [0:0]
:zone_lan_output - [0:0]
:zone_lan_src_ACCEPT - [0:0]
:zone_lan_src_REJECT - [0:0]
:zone_wan_dest_ACCEPT - [0:0]
:zone_wan_forward - [0:0]
:zone_wan_input - [0:0]
:zone_wan_output - [0:0]
:zone_wan_src_REJECT - [0:0]
-A INPUT -j delegate_input 
-A FORWARD -j delegate_forward 
-A OUTPUT -j delegate_output 
-A delegate_forward -m comment --comment "user chain for forwarding" -j forwarding_rule 
-A delegate_forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT 
-A delegate_forward -i br-lan -j zone_lan_forward 
-A delegate_forward -i eth0 -j zone_wan_forward 
-A delegate_forward -i pppoe-wan -j zone_wan_forward 
-A delegate_forward -j reject 
-A delegate_input -i lo -j ACCEPT 
-A delegate_input -m comment --comment "user chain for input" -j input_rule 
-A delegate_input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT 
-A delegate_input -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -j syn_flood 
-A delegate_input -i br-lan -j zone_lan_input 
-A delegate_input -i eth0 -j zone_wan_input 
-A delegate_input -i pppoe-wan -j zone_wan_input 
-A delegate_output -o lo -j ACCEPT 
-A delegate_output -m comment --comment "user chain for output" -j output_rule 
-A delegate_output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT 
-A delegate_output -o br-lan -j zone_lan_output 
-A delegate_output -o eth0 -j zone_wan_output 
-A delegate_output -o pppoe-wan -j zone_wan_output 
-A reject -p tcp -j REJECT --reject-with tcp-reset 
-A reject -j REJECT --reject-with icmp-port-unreachable 
-A syn_flood -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -m limit --limit 25/sec --limit-burst 50 -j RETURN 
-A syn_flood -j DROP 
-A zone_lan_dest_ACCEPT -o br-lan -j ACCEPT 
-A zone_lan_forward -m comment --comment "user chain for forwarding" -j forwarding_lan_rule 
-A zone_lan_forward -m comment --comment "forwarding lan -> wan" -j zone_wan_dest_ACCEPT 
-A zone_lan_forward -j zone_lan_src_REJECT 
-A zone_lan_input -m comment --comment "user chain for input" -j input_lan_rule 
-A zone_lan_input -j zone_lan_src_ACCEPT 
-A zone_lan_output -m comment --comment "user chain for output" -j output_lan_rule 
-A zone_lan_output -j zone_lan_dest_ACCEPT 
-A zone_lan_src_ACCEPT -i br-lan -j ACCEPT 
-A zone_lan_src_REJECT -i br-lan -j reject 
-A zone_wan_dest_ACCEPT -o eth0 -j ACCEPT 
-A zone_wan_dest_ACCEPT -o pppoe-wan -j ACCEPT 
-A zone_wan_forward -j MINIUPNPD 
-A zone_wan_forward -m comment --comment "user chain for forwarding" -j forwarding_wan_rule 
-A zone_wan_forward -j zone_wan_src_REJECT 
-A zone_wan_input -m comment --comment "user chain for input" -j input_wan_rule 
-A zone_wan_input -p tcp -m tcp --dport 51413 -m comment --comment "51413" -j ACCEPT 
-A zone_wan_input -p udp -m udp --dport 51413 -m comment --comment "51413" -j ACCEPT 
-A zone_wan_input -p tcp -m tcp --dport 9091 -m comment --comment "9091" -j ACCEPT 
-A zone_wan_input -p udp -m udp --dport 68 -m comment --comment "Allow-DHCP-Renew" -j ACCEPT 
-A zone_wan_input -p icmp -m icmp --icmp-type 8 -m comment --comment "Allow-Ping" -j ACCEPT 
-A zone_wan_input -j zone_wan_src_REJECT 
-A zone_wan_output -m comment --comment "user chain for output" -j output_wan_rule 
-A zone_wan_output -j zone_wan_dest_ACCEPT 
-A zone_wan_src_REJECT -i eth0 -j reject 
-A zone_wan_src_REJECT -i pppoe-wan -j reject 
COMMIT