規則鏈與策略:
規則:
ACCEPT：允許通過
LOG：記錄日誌
REJECT：拒絕通過，給出返回值
DROP：丟棄
規則鏈:
PREROUTING：路由前處理
INPUT：處理入站數據
OUTPUT：處理出站數據
FORWARD：處理轉發數據
POSTROUTING：路由後處理
raw表：確定是否對數據包狀態跟蹤
mangle表：設置標記
nat表：修改數據包源、目標IP或端口
filter表：過濾
規則順序
規則表先後順序：raw表→mangle表→nat表→filter表
規則鏈先後順序：
入站：PREROUTING→INPUT
出站：OUTPUT→POSTROUTING
轉發：PREROUTING→FORWARD→POSTROUTING
基本參數：
iptables [-t 表名] 選項 [鏈名] [條件] [控制類型]
Usage: iptables -[ACD] chain rule-specification [options]
iptables -I chain [rulenum] rule-specification [options]
iptables -R chain rulenum rule-specification [options]
iptables -D chain rulenum [options]
iptables -[LS] [chain [rulenum]] [options]
iptables -[FZ] [chain] [options]
iptables -[NX] chain
iptables -E old-chain-name new-chain-name
iptables -P chain target [options]
iptables -h (print this help information)
Commands:
Either long or short options are allowed.
--append -A chain Append to chain
--check -C chain Check for the existence of a rule
--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 [rulenum]]
List the rules in a chain or all chains
--list-rules -S [chain [rulenum]]
Print the rules in a chain or all chains
--flush -F [chain] Delete all rules in chain or all chains
--zero -Z [chain [rulenum]]
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)
Options:
--ipv4 -4 Nothing (line is ignored by ip6tables-restore)
--ipv6 -6 Error (line is ignored by iptables-restore)
[!] --protocol -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)
--goto -g chain
jump to chain with no return
--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
--wait -w wait for the xtables lock
--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.基本使用方法：
查看已有規則：
iptables -L
清空所有規則：
iptables -F
拒絕INPUT
iptables -P INPUT DROP
允許所有ping：
iptables -I INPUT -p icmp -j ACCEPT
在末尾加入允許未被其他規則匹配的數據包：
iptables -t filter -A INPUT -j -ACCEPT
刪除INPUT第二條規則：
iptables -D INPUT 2
僅允許來自172.27.8.0/22的用戶連接ssh服務
iptables -I INPUT -s 172.27.8.0/22 -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j REJECT
不允許任何用戶訪問本機3306端口
iptables -I INPUT -p tcp --dport 3306 -j REJECT
iptables -I INPUT -p udp --dport 3306 -j REJECT
拒絕其他用戶通過網卡eth1訪問本機http服務
iptables -I INPUT -i eth1 -p tcp --dport 80 -j REJECT
禁止用戶訪問www.baidu.com
iptables -I FORWARD -d www.baidu.com -j DROP
禁止172.27.8.22的用戶上網
iptables -I FORWARD -s 172.27.8.22 -j DROP
流量均衡：
將訪問流量分流至內網三臺不同主機：
iptables -A PREROUTING -i eth1 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT -to-destination 172.27.8.10
iptables -A PREROUTING -i eth1 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT -to-destination 172.27.8.20
iptables -A PREROUTING -i eth1 -p tcp --dport 80 -m state --state NEW -m nth --counter 0 --every 3 --packet 0 -j DNAT -to-destination 172.27.8.30使用上述操作，規則僅當前有效，如需重啓依然有效，執行service iptables save 將規則寫入/etc/sysconfig/iptables中
順便再貼一個iptables配置：
# Generated by iptables-save v1.4.7 on Thu Apr 16 01:33:03 2015
*filter
:INPUT DROP [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
#允許本機迴環地址
-A INPUT -i lo -p all -j ACCEPT
##允許這些IP所有操作
-A INPUT -s 110.122.120.54/32 -j ACCEPT
-A INPUT -s 110.122.120.98/32 -j ACCEPT
##允許DNS解析
-A INPUT -p udp --sport 53 -j ACCEPT
#允許5672端口訪問
-A INPUT -s 10.10.2.160 -p tcp --sport 5672 -j ACCEPT
##禁止eth0上27017入站和出站
-A INPUT -i eth0 -p tcp --dport 27017 -j DROP
-A OUTPUT -o eth0 -p tcp --sport 27017 -j DROP
##允許zabbix的10050端口
-A INPUT -s 100.10.2.160 -p tcp --dport 10050 -j ACCEPT
##運許snmp的161端口
-A INPUT -s 100.10.2.160 -p tcp --dport 10050 -j ACCEPT
##允許程序主機訪問指定IP的4506端口
-A INPUT -s 172.27.1.75 -p tcp --dport 4506 -j ACCEPT
##允許下列端口訪問
-A INPUT -p tcp --dport 8080 -j ACCEPT
-A INPUT -p tcp --dport 8090 -j ACCEPT
-A INPUT -p tcp --dport 13000 -j ACCEPT
-A INPUT -p tcp --dport 9000 -j ACCEPT
-A INPUT -p tcp --dport 8888 -j ACCEPT
COMMIT
