2514 Router
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname horton
!
enable secret 5 $1$GwRz$YS/82LXSYcgD1d5Nua9Ob1
enable password ww
!
ip subnet-zero
!
ip inspect name ethernetin cuseeme timeout 3600
ip inspect name ethernetin ftp timeout 3600
ip inspect name ethernetin h323 timeout 3600
ip inspect name ethernetin http timeout 3600
ip inspect name ethernetin rcmd timeout 3600
ip inspect name ethernetin realaudio timeout 3600
ip inspect name ethernetin smtp timeout 3600
ip inspect name ethernetin sqlnet timeout 3600
ip inspect name ethernetin streamworks timeout 3600
ip inspect name ethernetin tcp timeout 3600
ip inspect name ethernetin tftp timeout 30
ip inspect name ethernetin udp timeout 15
ip inspect name ethernetin vdolive timeout 3600
!
interface Ethernet0
ip address 20.20.20.2 255.255.255.0
ip access-group 101 in
no ip directed-broadcast
ip nat inside
ip inspect ethernetin in
!
interface Ethernet1
no ip address
no ip directed-broadcast
shutdown
!
interface Serial0
ip address 150.150.150.1 255.255.255.0
ip access-group 112 in
no ip directed-broadcast
ip nat outside
clockrate 4000000
!
interface Serial1
no ip address
no ip directed-broadcast
shutdown
!
ip nat pool serialzero 150.150.150.3 150.150.150.255 netmask 255.255.255.0
ip nat inside source list 1 pool serialzero
ip classless
ip route 0.0.0.0 0.0.0.0 150.150.150.2
ip route 20.30.30.0 255.255.255.0 20.20.20.1
!
access-list 1 permit 20.0.0.0 0.255.255.255
access-list 101 permit tcp 20.0.0.0 0.255.255.255 any
access-list 101 permit udp 20.0.0.0 0.255.255.255 any
access-list 101 permit icmp 20.0.0.0 0.255.255.255 any
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 unreachable
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 echo-reply
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 packet-too-big
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 time-exceeded
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 traceroute
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 administratively-prohibited
access-list 112 permit icmp any 150.150.150.0 0.0.0.255 echo
access-list 112 permit tcp host 150.150.150.2 host 150.150.150.1 eq telnet
access-list 112 deny ip 127.0.0.0 0.255.255.255 any
access-list 112 deny ip any any
!
line con 0
transport input none
line aux 0
line vty 0 4
password ww
login
!
end
关于ip inspect name
if you deny SMTP mail on the external ACL, no external SMTP servers will ever be able to make a connection to the internal SMTP server.
CBAC is totally independent of access lists - CBAC is associated with ACLs because one function of CBAC is to ensure return traffic of a
session is permitted back to the source - however don't confuse CBAC by thinking ACLs are required. If you apply an inspect list to an interface, inspection takes place, no matter what ACLs are or are not in place. However, remember that ACLs are processed first, so the ACL must allow through the appropriate traffic to be passed thru to the inspection list.
I'm guessing your config would look something like this:
! Internal Interface
Interface e0 ip inspect WEB inbound
! External Interface
Interface e1 ip access-group 100 in
ip inspect SMTP inbound
access-list 100 permit tcp any host x.x.x.x eq smtp
access-list 100 deny ip any any
ip inspect name WEB http
ip inspect name WEB ftp
ip inspect name WEB smtp
ip inspect name WEB tcp
ip inspect name WEB udp
ip inspect name SMTP smtp
On your external ACL, you must have an opening to allow SMTP in - there is no way CBAC can automatically do this for you as traffic is first processed by the ACL and must pass. So once the SMTP traffic is allowed
in, it is passed to the inspection list SMTP, which applys SMTP protocol-based inspection (and opens up any ACLs if necessary - in this
example this function is not required).
Note that in this example you could place the SMTP inspection list on the internal interface in the outbound direction as well. This is a better placement option if you had say a DMZ interface that was also
receiving SMTP mail for the internal SMTP server, as you would only require a single inspection point (outbound on the internal interface)
rather than inbound on the external and DMZ interfaces.