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ACLs (Access Control Lists). Detailed in Doyle Appendix B Numbered ACLs 1-99 standard IP ACLs 100-199 extended IP ACLs (other types for other protocols we will not use like Appletalk, IPX, DECnet, MAC addr, etc.) Named ACLs (IOS 11.2 and newer). Numbered Standard IP ACL.
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ACLs (Access Control Lists) • Detailed in Doyle Appendix B • Numbered ACLs • 1-99 standard IP ACLs • 100-199 extended IP ACLs • (other types for other protocols we will not use like Appletalk, IPX, DECnet, MAC addr, etc.) • Named ACLs (IOS 11.2 and newer)
Numbered Standard IP ACL • Access-list 5 permit 128.186.0.0 0.0.255.255 • Access-list 5 permit 204.194.36.243 0.0.0.0 • Access-list 5 deny 0.0.0.0 255.255.255.255 • Access-list 5 permit 128.186.0.0 0.0.255.255 • Access-list 5 permit host 204.194.36.243 • Access-list 5 deny any
Numbered Extended IP ACL • Access-list 103 permit tcp any any established • Access-list 103 permit tcp any host 128.186.5.2 eq 80 • Access-list 103 permit tcp any host 128.186.5.3 eq 25 • Access-list 103 permit icmp any any • Access-list 103 deny ip any any
Named Extended IP ACL • ip access-list extended firewall • remark Allow established connections from inside • permit tcp any any established • remark Allow Internet access to WWW server • permit tcp any host 128.186.5.2 eq 80 • remark Allow Internet access to Email server • permit tcp any host 128.186.5.3 eq 25 • remark Allow PING, Traceroute, etc. • permit icmp any any • remark Restrict anything else • deny any any (redundant due to implicit deny any any)
Lockout Prevention • Router#write • Building configuration... • [OK] • Router#reload in 5 • Reload scheduled for 11:53:52 EST Thu Feb 3 2005 (in 5 minutes) • Proceed with reload? [confirm]y • Feb 3 11:48:53 EST: %SYS-5-SCHEDULED_RELOAD: Reload requested for 11:53:52 • Router#conf t • Router(config)#ip access-list extended firewall • Router(config-ext-nacl)#permit tcp any any established • Router(config-ext-nacl)#permit tcp any host 128.186.5.2 eq 80 • Router(config-ext-nacl)#permit tcp any host 128.186.5.3 eq 25 • Router(config-ext-nacl)#permit icmp any any • Router(config-ext-nacl)#int e0/0 • Router(config-if)#ip access-group firewall in • Router(config-if)#^Z • Router# • Feb 3 11:50:04 EST: %SYS-5-CONFIG_I: Configured from console by console • Router#reload cancel • Router# • *** • *** --- SHUTDOWN ABORTED --- • *** • Feb 3 11:50:08 EST: %SYS-5-SCHEDULED_RELOAD_CANCELLED: • Scheduled reload cancelled at 11:50:08 EST Thu Feb 3 2005
Applying ACL to interface • no ip access-list extended firewall • ip access-list extended firewall • permit tcp any any established • permit tcp any host 128.186.5.2 eq 80 • permit tcp any host 128.186.5.3 eq 25 • permit icmp any any • interface serial0 • ip access-group firewall in