网络防火墙
自定义链 链管理: -N:new, 自定义一条新的规则链 -X:delete,删除自定义的空的规则链 -P:Policy,设置默认策略;对filter表中的链而言,其默认策略有: ACCEPT:接受 DROP:丢弃 -E:重命名自定义链;引用计数不为0的自定义链不能够被重命名,也不能被删除 iptables/netfilter网络防火墙: (1) 充当网关 (2) 使用filter表的FORWARD链 注意的问题: (1) 请求-响应报文均会经由FORWARD链,要注意规则的方向性 (2) 如果要启用conntrack机制,建议将双方向的状态为ESTABLISHED的报文直接放行 准备: firewall:开启ip_forward功能 [root@firewall ~]#vim /etc/sysctl.conf net.ipv4.ip_forward = 1 [root@firewall ~]#sysctl -p [root@firewall ~]#sysctl -a firewall开启转发功能后,10.0.0.108能互相ping通192.168.37.122 示例:
场景:把对外访问的策略配置在自定义链中:
1、新建链,专用添加访问外网策略
1 [root@firewall-121 ~]# iptables -N TOINTERNET 2 [root@firewall ~]# iptables -vnL --line-numbers 3 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) 4 num pkts bytes target prot opt in out source destination 5 1 6 394 ACCEPT tcp -- * * 0.0.0.0/0 10.0.0.108 tcp dpt:80 6 2 22 2089 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 7 3 105 6996 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable 8 9 Chain TOINTERNET (0 references)View Code
2、在新链中添加策略
1 [root@firewall-121 ~]# iptables -A TOINTERNET -s 10.0.0.108 -p tcp --dport 80 -j ACCEPT 2 [root@firewall-121 ~]# iptables -A TOINTERNET -s 10.0.0.108 -p icmp --icmp-type 8 -j ACCEPTView Code
3、把新链关联到FORWARD链中
1 [root@firewall-121 ~]# iptables -I FORWARD 1 -j TOINTERNET 2 [root@firewall-121 ~]# iptables -vnL --line-numbers 3 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) 4 num pkts bytes target prot opt in out source destination 5 1 26 2246 TOINTERNET all -- * * 0.0.0.0/0 0.0.0.0/0 6 2 6 394 ACCEPT tcp -- * * 0.0.0.0/0 10.0.0.108 tcp dpt:80 7 3 33 3287 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 8 4 106 7056 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable 9 10 Chain TOINTERNET (1 references) 11 num pkts bytes target prot opt in out source destination 12 1 12 796 ACCEPT tcp -- * * 10.0.0.108 0.0.0.0/0 tcp dpt:80 13 2 3 252 ACCEPT icmp -- * * 10.0.0.108 0.0.0.0/0 icmptype 8View Code
4、验证新chain策略有效性
1 [root@CentOS7-108 ~]# curl 192.168.37.122 2 internet server 3 [root@CentOS7-108 ~]# ping 192.168.37.122 4 64 bytes from 192.168.37.122: icmp_seq=1 ttl=63 time=0.551 msView Code 标签:自定义,chain,--,0.0,防火墙,ACCEPT,firewall,root From: https://www.cnblogs.com/cnblogsfc/p/14181749.html