Netband Project - IOS firewall

<accesscontrol>NetBand</accesscontrol> This page is part of the Netband Project

Context Based Access Control (CBAC)

• filters TCP and UDP packets based on application-layer protocol session information.
• more flexible than access control lists, that checks packets at the network layer, or at most, the transport layer
• inspects packet sequence numbers in TCP connections
• detects unusually high rates of new connections and issue alert messages.
• creates temporary openings in the return acl to allow traffic back in.

CBAC

Configuration

• Note: The router only keeps track of the configured protocols. Unconfigured protocols are allowed through without inspection or tracking if the interface acls permit

 ip inspect audit-trail 
 ip inspect name iosfw ftp
 ip inspect name iosfw tcp
 ip inspect name iosfw udp
 ip inspect name iosfw http
 ip inspect name iosfw https
!
interface FastEthernet0/0
 description OUTSIDE
 ip inspect iosfw out
 ip access-group 101 in
!
 access-list 101 permit udp any eq isakmp any eq isakmp
 access-list 101 permit esp any any
 access-list 101 permit tcp any any eq 22
 access-list 101 deny   ip any any log

Verification

B1rt1#sh ip inspect sessions
Established Sessions
 Session 65E14830 (10.2.1.10:3935)=>(195.137.194.128:80) http SIS_OPEN
 Session 65E15310 (10.2.1.10:3936)=>(195.137.194.128:80) http SIS_OPEN
 Session 65E15058 (10.2.1.10:3937)=>(195.137.194.128:80) http SIS_OPEN
 Session 65E155C8 (10.2.1.10:3934)=>(195.137.194.128:80) http SIS_OPEN

• Syslog audit trail

Apr 27 10:22:06.521: %FW-6-SESS_AUDIT_TRAIL_START: Start http session: initiator (10.2.1.10:3898) -- responder (195.137.194.128:80)
Apr 27 10:22:18.044: %FW-6-SESS_AUDIT_TRAIL: Stop http session: initiator (10.2.1.10:3898) sent 1247 bytes -- responder (195.137.194.128:80) sent 144791 bytes

Apr 27 10:48:36.770: %FW-6-SESS_AUDIT_TRAIL_START: Start tcp session: initiator (10.2.1.10:3958) -- responder (192.168.1.1:23)
Apr 27 10:49:30.769: %FW-6-SESS_AUDIT_TRAIL: Stop tcp session: initiator (10.2.1.10:3958) sent 74 bytes -- responder (192.168.1.1:23) sent 255 bytes

Intrusion Prevention System (IPS)

• See Netband Project - IOS ips for further information and configuration

Port to Application Mapping (PAM)

• customize TCP or UDP port numbers for network services or applications.
• information in the PAM table enables CBAC supported services to run on nonstandard ports
• allows cbac to track user customized ports

Configuration

ip port-map http port tcp 8001 description Alternative http port
...
ip inspect name iosfw http
...

• The same port can be mapped to different services on different hosts

access-list 10 permit 10.2.1.10
access-list 20 permit 10.2.1.11
ip port-map http port 8001 list 10
ip port-map http ftp 8001 list 20

• User-defined port map

ip port-map user-streaming port tcp 8000 description Custom Video Streaming port
...
ip inspect name iosfw user-streaming
...

Verification

B1rt1#sh ip port-map http
Default mapping:  http                 tcp port 80                         system defined
Default mapping:  http                 tcp port 8001                       user defined

B1rt1#sh ip port-map
...
Default mapping:  user-streaming       tcp port 8000                       user defined
...

External Links

Cisco IOS Security Configuration Guide