简单防火墙

　　 
　　interface Ethernet 0/0 ! Mosbach lokal
　　ip address 129.143.204.13 255.255.255.252
　　description Ethernet zum RZ-Router
　　no ip directed-broadcast ! wg. Hacker (denial of service)

　　ip inspect FIWA in ! Ueberpruefung des IP-Verkehrs
　　ip aclearcase/" target="_blank" >ccess-group 101 in ! Anti-Spoofing
　　ip access-group 102 out ! zusaetzliches Welt-LAN-Filter wegen Servern
　　no shutdown
　　!
　　no access-list 101
　　access-list 101 permit tcp 129.143.204.12 0.0.0.3 any ! RZ-Router Anti-Spoofing
　　access-list 101 permit udp 129.143.204.12 0.0.0.3 any ! RZ-Router Anti-Spoofing
　　access-list 101 permit icmp 129.143.204.12 0.0.0.3 any ! RZ-Router Anti-Spoofing
　　access-list 101 permit tcp 193.196.5.0 0.0.0.255 any ! Netz der BA-Mo Anti-Spoofing
　　access-list 101 permit udp 193.196.5.0 0.0.0.255 any ! Netz der BA-Mo Anti-Spoofing
　　access-list 101 permit icmp 193.196.5.0 0.0.0.255 any ! Netz der BA-Mo Anti-Spoofing
　　access-list 101 deny ip any any
　　!
　　! Zulassen von gewissen Diensten auf die Server
　　no access-list 102
　　!
　　access-list 102 permit tcp any any eq 22 ! SSH
　　access-list 102 permit tcp any any eq 113 ! Ident
　　access-list 102 permit tcp any any eq 487 ! SAFT
　　!
　　permit tcp any gt 1023 host 193.196.5.107 eq 21 ! FTP-Commands (fuer PASV FTP)
　　permit tcp any gt 1023 host 193.196.5.105 eq 21 ! FTP-Commands (fuer PASV FTP)
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 25 ! SMTP zulassen
　　access-list 102 permit tcp any host 193.196.5.105 eq 25 ! SMTP zulassen
　　!
　　access-list 102 permit tcp host 129.143.2.1 host 193.196.5.107 eq 53 ! DNS Zone-Transfer
　　access-list 102 permit tcp host 129.206.100.126 host 193.196.5.107 eq 53 ! DNS Zone-Transfer
　　access-list 102 permit tcp host 129.206.100.127 host 193.196.5.107 eq 53 ! DNS Zone-Transfer
　　access-list 102 permit tcp host 129.143.2.1 host 193.196.5.105 eq 53 ! DNS Zone-Transfer
　　access-list 102 permit tcp host 129.206.100.126 host 193.196.5.105 eq 53 ! DNS Zone-Transfer
　　access-list 102 permit tcp host 129.206.100.127 host 193.196.5.105 eq 53 ! DNS Zone-Transfer
　　
　　access-list 102 permit permit tcp any host 193.196.5.107 eq 80 ! WWW
　　access-list 102 permit permit tcp any host 193.196.5.105 eq 80 ! WWW
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 119 ! nntp
　　access-list 102 permit tcp any host 193.196.5.105 eq 119 ! nntp
　　!
　　access-list 102 permit udp any host 193.196.5.107 eq 123 ! ntp
　　access-list 102 permit udp any host 193.196.5.105 eq 123 ! ntp
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 389 ! ldap
　　access-list 102 permit tcp any host 193.196.5.105 eq 389 ! ldap
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 443 ! https
　　access-list 102 permit tcp any host 193.196.5.105 eq 443 ! https
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 993 ! Secure-IMAP
　　access-list 102 permit tcp any host 193.196.5.105 eq 993 ! Secure-IMAP
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 995 ! Secure-POP3
　　access-list 102 permit tcp any host 193.196.5.105 eq 995 ! Secure-POP3
　　!
　　! bei geringeren Sicherheitsanforderungen:
　　!
　　access-list 102 permit tcp any host 193.196.5.107 eq 110 ! POP3 zulassen
　　access-list 102 permit tcp any host 193.196.5.105 eq 110 ! POP3 zulassen
　　access-list 102 permit udp any host 193.196.5.105 eq 53 ! DNS-Anfragen
　　access-list 102 permit udp any host 193.196.5.107 eq 53 ! DNS-Anfragen
　　!
　　!
　　access-list 102 permit icmp any host 193.196.5.107 administratively-prohibited
　　access-list 102 permit icmp any host 193.196.5.107 echo
　　access-list 102 permit icmp any host 193.196.5.107 echo-reply
　　access-list 102 permit icmp any host 193.196.5.107 packet-too-big
　　access-list 102 permit icmp any host 193.196.5.107 time-exceeded
　　access-list 102 permit icmp any host 193.196.5.107 traceroute
　　access-list 102 permit icmp any host 193.196.5.107 unreachable
　　access-list 102 deny ip any any
　　!
　　ip inspect name FIWA http java-list 50 ! JavaScript ablehnen nach ACL 50
　　ip inspect name FIWA realaudio timeout 3600
　　ip inspect name FIWA smtp timeout 3600
　　ip inspect name FIWA tftp timeout 30
　　ip inspect name FIWA ftp timeout 3600
　　ip inspect name FIWA udp timeout 15
　　ip inspect name FIWA tcp timeout 3600
　　!
　　no access-list 50
　　access-list 50 permit any log
　　
　　评:虽然是很好.但是访问列表过多,一旦被DOS一攻可能路由器马上瘫痪…重启…所以我认为要在前面加多一台Router来做个TCP Intercept 来拦截DOS攻击.如下:
　　假如管理到个服务器群网络上192.168.111.0 & 192.168.112.0 内的目标主机的TCP连接请求.使用拦截模式,随机丢弃连接:
　　access-list 123 permit tcp any 192.168.111.0 0.0.0.255
　　access-liat 123 permit tcp any 192.168.112..0 0.0.0.255
　　ip tcp intercept list 123
　　ip tcp intercept mode intercept
　　ip tcp intercept drop-mode random
　　
　　做好以后.两个Router在做个HSRP ……..
　　
　　这样还可以嘛…呵呵….

原文转自：http://www.ltesting.net