Cisco IOS Zone-Based Firewall

• Classic IOS, inspection policies were applied to all traffic on that interface,
• we can't apply to different policies to different groups of users.
• Zone-based firewall (ZFW), available in IOS release 12.4(6)T or later.
• This concept(ZFW) is similar to that used by appliance firewalls.
• Router interfaces are placed into security zones.
• Traffic between zones were blocked by default.
• Some times traffic blocked between interfaces that have been assigned to a security zone & those that have not.
• We must explicitly apply a policy to allow traffic between zones.
• Zone policies are configured using the Class-based Policy Language(CPL), 
• which is similar to Modular QoS Command Line Interface (MQC) 
• in its use of class maps and policy maps.
• Class maps let you configure highly granular policies if needed.
• A new class & policy map type, the inspect type, is introduced for zone-based firewalls.
• 
  
• 
  

Cisco IOS Firewall Configuration Steps

CBAC configuration steps:

• Choose an interface (inside or outside).
• Configure an ip access list that denies all traffic to be inspected.
• Configure global timeouts & thresholds using the ip inspect commands.
• Define an inspection rule & an optional rule-specific timeout value using the ip inspect name protocol commands.
• Apply the inspection rule to an interface.
• Apply the access list to the same interface as the inspection rule, but in the opposite direction(inbound or outbound)

Cisco IOS Firewall Caveats(limitations)

• Caveats are powerful as CBAC is for dynamic inspection and filtering.
• it has also some limitations.
• CBAC comes after Access-list filters are applied to an interface.
• if an access list blocks a particular type of traffic on an interface,
• where you are using CBAC to inspect inbound traffic,
• that traffic will be denied before CBAC sees it.
• CBAC cannot protect against attacks that originate inside your network.
• CBAC works only on protocols that you specified,
• leaving all other traffic to access lists & other filtering methods.
• To inspect traffic other than TCP & UDP transported traffic,
• you must configure a named inspection rule.
• CBAC does not inspect traffic destined to or  originated from the firewall router itself,
• only that traverses the firewall router.
• CBAC has restrictions on handling encrypted traffic.

Cisco IOS Firewall protocol Support

• An IOS firewall can inspect a long list of protocols when CBAC was used.
• Common protocols that CBAC can inspects are:
• Any generic TCP session, regardless of application layer protocol
• All UDP "sessions"
• FTP
• SMTP
• TFTP
• H.323 (NetMeeting, ProShare, and so on)
• Java
• CU-SeeMe
• UNIX R commands (rlogin, rexec, rsh, and so on)
• RealAudo
• Sun RPC
• SQL*Net
• StreamWorks
• VDOLive