Cisco IOS Firewall-H.323 V3 V4 Support

Last Updated: January 20, 2012

The H.323 V3/V4 Support feature provides the Cisco IOS firewall with support for the H.323 Voice over IP (VoIP) Version 3 and Version 4 protocols. With Version 3 and Version 4 support, features like call signaling (H.225) over User Datagram Protocol (UDP), multiple call signaling over a single TCP connection, T.38 Fax over TCP, and address resolution using border elements are supported. Support for a rate-limiting mechanism to monitor call attempt rate and call aggregation is also introduced and can be enabled.

H.323 is a multiprotocol and multichannel suite. Channel negotiation parameters are embedded inside encoded H.323 control messages. The Base H.323 Application Layer Gateway (ALG) Support feature provides support in Cisco IOS firewall environments to process the H.323 control messages.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for Cisco IOS Firewall-H.323 V3 V4 Support

Restrictions for Cisco IOS Firewall-H.323 V3 V4 Support

General

  • Inspection of H.323 signaling over secure (encrypted) channel is not supported.

ASR 1000 Series Routers

  • Support is provided for gateway terminals using the H.323v4 with H.225v4 and H.245v7 protocols only.
  • Backward compatibility is provided for H.323v2 messages only. H.323v1 messages are ignored.
  • Multipoint conferencing, managed by the Multipoint Control Unit (MCU), is not supported.
  • The T.120 protocol is not supported.
  • Cisco IOS firewall support is limited to H.323 Direct Call Signaling and H.225 RAS Call Signaling only.

Information About Cisco IOS Firewall-H.323 V3 V4 Support

H.323 and H.225 RAS Implementation

H.225 Registration, Admission, and Status (RAS) signaling in Cisco IOS firewalls is a signaling protocol that is used between endpoints (such as gateways) and gatekeepers. The H.225 standard is used by H.323 for call setup. H.225 includes RAS control, which is used to communicate with the gatekeeper. A RAS signaling channel enables connections between the gatekeeper and H.323 endpoints.

H.323 and H.245 Protocol

During the call setup between H.323 terminals, the following protocols are used:

  • H.225 Call Signaling
  • H.245 Call Control

Both protocol messages contain embedded IP addresses and ports. Any message passing through a router running Cisco IOS firewall must be decoded, inspected, and encoded back to the packet.

In order for an H.323 call to take place, an H.225 connection on TCP port 1720 needs to be opened. When the H.225 connection is opened, the H.245 session is initiated and established. This connection can take place on a separate channel from the H.225 or it can be done using H.245 tunneling on the same H.225 channel whereby the H.245 messages are embedded in the H.225 messages and set on the previously established H.225 channel.

If the H.245 tunneled message is not understood the Cisco IOS firewall cannot translate the message, which causes a failure in media traffic. H.245 FastConnect procedures will not help because FastConnect is terminated as soon as an H.245 tunneled message is sent.

H.323 Version 3 and Version 4 Features Supported

The table below lists the H.323 Version 3 and Version 4 features supported by Cisco IOS firewall. For information on the H.323 standard, see the Standards section.


Note
On the ASR 1000 series routers Cisco IOS firewall support is limited to H.323 Direct Call Signaling and H.225 RAS Call Signaling only.

Table 1 H.323 Standards Features Supported by Cisco IOS Firewall

Standard

Features Supported by Cisco IOS Firewall

H.323 Version 3

  • Caller ID
  • Annex E--Protocol for Multiplexed Call Signaling Transport
  • Annex G--Communication Between Administrative Domains
  • Generic information transport
  • Maintaining and reusing connections using call signaling channel
  • Supplementary services (call hold, call park and call pickup, message waiting indication, and call waiting)

H.323 Version 4

  • Additive registrations
  • Alternate gatekeepers
  • Endpoint capacity
  • Bandwidth management
  • Usage information reporting
  • Generic extensibility framework
  • Indicating desired protocols
  • Call status reporting
  • Enhancements to Annex D (Real-Time Fax)
  • QoS support for H.323 enhancements
  • Dual Tone Multifrequency (DTMF) digit transmission using Real-Time Protocol (RTP)

Base H.323 ALG Support

The Base H.323 ALG Support feature provides support for ALGs to perform protocol specific issues such as processing embedded IP address and port numbers and extracting connection and session information from control channels and sessions.

Encoded channel-negotiation parameters are embedded in H.323 control messages. In Cisco IOS firewall environments, the system must intercept these messages and invoke the H.323 ALG to process the messages.

The H.323 ALG performs the following tasks to process the messages:

  • Intercepts the H.323 control messages on the H.225.0 TCP port 1720 and on the dynamically negotiated H.245 TCP port.
  • Decodes the intercepted control messages.
  • Parses the decoded control messages, identifies the embedded IP address and port-number pairs and builds action info tokens based on the IP address and port-number pairs.
  • Sends the action info tokens to the Cisco IOS firewall for processing.

The Cisco IOS firewall performs the actions indicated by the action info tokens. The actions performed include session and door entry lookup, creation, and deletion, or address and port translation. When the Cisco IOS firewall completes the action, it fills the action-result field in the action-info token, with the translated IP address and port number, or with an action failure indicator. Cisco IOS firewall then adds a flag to indicate if the packet should be dropped or forwarded. Finally, it returns the action info token to the H.323 ALG.

  • Receives the modified action info token from the Cisco IOS firewall and either drops or forwards the packet based on information in the action info token.

The table below lists the H.323 control messages processed by the Base H.323 ALG Support feature. For more information on the H.323 standard, see the Standards section.

Table 2 H.323 Control Messages Processed by Base H.323 ALG Support

Protocol

Messages

H.225.0 Call Signalling

  • Setup
  • Alert
  • Call proceed
  • Connect
  • Facility
  • Progress
  • Empty
  • ReleaseComplete
  • SetupAcknowlege

H.245 Media Control

Note    If tunnelling mode is enabled H.245 messages may be embedded within H.225.0 messages
  • OpenLogicalChannel
  • OpenLogicalAck
  • CloseLogicalChannel
  • CloseLogicalAck

Support of Rate Limiting Mechanism

In addition to supporting Version 3 and Version 4 of the H.323 protocol, support is introduced for a rate-limiting mechanism to monitor call attempt rate and call aggregation. Rate limiting is more important for voice applications where gateways and gatekeepers are set up in less secure arrangements such as a Demilitarized Zone (DMZ). A DMZ can be vulnerable to attack from the Internet.

Rate Limiting of H.323 Traffic Messages

Rate limiting of H.323 traffic control messages is based on actions on H.323 class maps. The messages that are to be rate limited are specified through match message statements within the class map. The rate-limit threshold value is specified by a rate limit command, as an action on the H.323 class map. The rate limit command limits the message attempt rate; it limits the number of H.323 messages being sent per second to and from an end point. Rate Limiting can be used to control call attempt rate.


Note
While configuring the rate-limit command, do not configure the allow or reset commands. An error message is displayed if you try to configure the allow or reset commands while configuring the rate-limit command and vice versa.

How to Configure Cisco IOS Firewall-H.323 V3 V4 Support

Configuring a Firewall Policy for H.323 Traffic

Configuring a Class Map for H.323 Traffic

Perform this task to define the class map that for H.323 traffic that is to be permitted between zones.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    class-map type inspect [match-any | match-all] class-map-name

4.    match protocol protocol-name [parameter-map] [signature]

5.    match protocol h225ras

6.    match protocol h323-annexe

7.    match protocol h323-nxg

8.    end


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
class-map type inspect [match-any | match-all] class-map-name


Example:

Router(config)# class-map type inspect match-any h323-traffic-class

 

Creates a Layer 3 and Layer 4 (Top Level) inspect type class map and enters class-map configuration mode.

 
Step 4
match protocol protocol-name [parameter-map] [signature]


Example:

Router(config-cmap)# match protocol h323

 

Configures the match criterion for a class map on the basis of the specified protocol.

 
Step 5
match protocol h225ras


Example:

Router(config-cmap)# match protocol h225ras

 

Configures the match criterion for a class map on the basis of a specified protocol.

Note    You should specify the h225ras keyword to create a class map for H.225 RAS protocol classification. For a list of supported protocols, use the command-line interface (CLI) help option (?) on your platform.
 
Step 6
match protocol h323-annexe

Example:

Router(config-cmap)# match protocol h323-annexe

 

Enables the inspection of H.323 Protocol Annex E traffic.

 
Step 7
match protocol h323-nxg

Example:

Router(config-cmap)# match protocol h323-nxg

 

Enables the inspection of H.323 Protocol Annex G traffic.

 
Step 8
end


Example:

Router(config-cmap)# end

 

Exits class-map configuration mode and enters privileged EXEC mode.

 

Configuring a Policy Map for H.323 Traffic

Perform this task to create a policy map for H.323 traffic.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    policy-map type inspect policy-map-name

4.    class type inspect class-map-name

5.    inspect [parameter-map-name]

6.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
policy-map type inspect policy-map-name


Example:

Router(config)# policy-map type inspect h323-policy

 

Creates a Layer 3 or Layer inspect type policy map.

 
Step 4
class type inspect class-map-name


Example:

Router(config)# class type inspect h323-traffic-class

 

Specifies the traffic (class) on which an action is to be performed.

Note    The class-map-name value must match the appropriate class map name specified via the class-map type inspectcommand.
 
Step 5
inspect [parameter-map-name]


Example:

Router(config)# inspect

 

Enables Cisco IOS stateful packet inspection.

Note    The actions drop or allow may also be used instead of the inspect command here.
 
Step 6
exit


Example:

Router(config)# exit

 

Exits global configuration mode and enters privileged EXEC mode.

 

Configuring a Zone-Pair for H.323 Traffic and Applying an H.323 Policy Map

Perform this task to configure a zone-pair for H.323 traffic and to apply an H.323 policy map to the traffic.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    zone security zone-pair-name

4.    exit

5.    zone security zone-pair-name

6.    exit

7.    zone security zone-pair-name

8.    exit

9.    zone-pair security zone-pair-name {source source-zone-name| self} destination [self | destination-zone-name]

10.    service-policy type inspect policy-map-name

11.    end


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
zone security zone-pair-name


Example:

Router(config) zone security in-out

 

Specifies the name of the zone-pair and enters security zone configuration mode.

 
Step 4
exit


Example:

Router(config-sec-zone) exit

 

Exits security zone configuration mode and enters global configuration mode.

 
Step 5
zone security zone-pair-name


Example:

Router(config) zone security inside

 

Creates the source zone from which traffic originates and enters security zone configuration mode.

 
Step 6
exit


Example:

Router(config-sec-zone) exit

 

Exits security zone configuration mode and enters global configuration mode.

 
Step 7
zone security zone-pair-name


Example:

Router(config) zone security outside

 

Creates the destination zone to which the traffic is bound and enters security zone configuration mode.

 
Step 8
exit


Example:

Router(config-sec-zone) exit

 

Enters global configuration mode.

 
Step 9
zone-pair security zone-pair-name {source source-zone-name| self} destination [self | destination-zone-name]


Example:

Router(config)# zone-pair security in-out source inside destination outside

 

Associates a zone-pair and declares the names of the routers from which traffic is originating (source) and to which traffic is bound (destination).

 
Step 10
service-policy type inspect policy-map-name


Example:

Router(config-sec-zone)# service-policy type inspect h323-policy

 

Attaches a firewall policy map to a zone-pair and enters security zone configuration mode.

 
Step 11
end


Example:

Router(config-sec-zone)# end

 

Exits security zone configuration mode and enters privileged EXEC mode.

 

Configuring Rate Limiting of H.323 Traffic Control Messages

Perform this task to configure a rate limit on H.323 traffic control messages.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    class-map type inspect protocol-name [match-any| match-all] class-map-name

4.    match message message-name

5.    exit

6.    policy-map type inspect protocol-name policy-map-name

7.    class type inspect protocol-name class-map-name

8.    rate-limit limit-number

9.    end


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
class-map type inspect protocol-name [match-any| match-all] class-map-name


Example:

Router(config)# class-map type inspect h323 match-any h323-ratelimit-class

 

Creates a Layer 7 (application-specific) inspect type class map and enters class-map configuration mode.

 
Step 4
match message message-name


Example:

Router(config-cmap)# match message setup

 

Configures the match criterion for a class map on the basis of H.323 protocol messages.

 
Step 5
exit


Example:

Router(config-cmap)# exit

 

Exits class-map configuration mode and returns to global configuration mode.

 
Step 6
policy-map type inspect protocol-name policy-map-name


Example:

Router(config)# policy-map type inspect h323 h323-ratelimit-policy

 

Creates a Layer 7 inspect type policy map and enters policy-map configuration mode.

 
Step 7
class type inspect protocol-name class-map-name


Example:

Router(config-pmap)# class type inspect h323 h323-ratelimit-class

 

Specifies the Layer 7 traffic (class) on which an action is to be performed and enters policy-map class configuration mode.

Note    The class-map-name value must match the appropriate class map name specified via the class-map type inspectcommand.
 
Step 8
rate-limit limit-number


Example:

Router(config-pmap-c)# rate limit 1000

 

Limits the number of messages that strike the Cisco IOS firewall every second.

 
Step 9
end


Example:

Router(config-cmap-c)# end

 

Exits policy-map class configuration mode and enters privileged EXEC mode.

 

Configuring Deep Packet Inspection on a Layer 3 Policy Map

Perform this task to configure deep packet inspection on a Layer 3 policy map.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    policy-map type inspect policy-map-name

4.    class type inspect class-map-name

5.    service-policy protocol-name policy-map-name

6.    end


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
policy-map type inspect policy-map-name


Example:

Router(config)# policy-map type inspect h323-policy

 

Creates a Layer 3 and Layer 4 inspect type policy map.

 
Step 4
class type inspect class-map-name


Example:

Router(config-pmap)# class type inspect h323-traffic-class

 

Specifies the traffic (class) on which an action is to be performed and enters policy-map configuration mode.

 
Step 5
service-policy protocol-name policy-map-name


Example:

Router(config-pmap-c)# service-policy h323 h323-ratelimit-policy

 

Attaches a Layer 7 policy map to a top-level policy map.

 
Step 6
end


Example:

Router(config-cmap-c)# end

 

Exits policy-map class configuration mode and enters privileged EXEC mode.

 

Configuration Examples for Cisco IOS Firewall-H.323 V3 V4 Support

Example Configuring a Voice Policy to Inspect H.323 Annex E Packets

The following example shows how to configure a voice policy to inspect the H.323 protocol Annex E packets for the "my-voice-class" class map: 

class-map type inspect match-all my-voice-class
 match protocol h323-annexe

Example Configuring a H.323 Class-Map to Match Specific Messages

The following example shows how to configure an H.323 specific class map to match H.225 setup or release-complete messages only: 

class-map type inspect h323 match-any my_h323_rt_msgs
 match message setup
 match message release-complete

Example Configuring a Voice Policy to Inspect H.323 Annex G Packets

The following example shows how to configure a voice policy to inspect the H.323 protocol Annex E packets for the "my-voice-class" class map: 

class-map type inspect match-all my-voice-class
 match protocol h323-nxg

Example Configuring a Voice Policy to Limit Call Attempt Rate

The following example shows how to configure a voice policy to limit the call attempt rate to 16 calls per second for the calls terminated at 192.168.2.1. 

access-list 102 permit ip any host 192.168.2.1 
!
class-map type inspect match-all my_voice_class
 match protocol h323
 match access-group 102
!
class-map type inspect h323 match-any my_h323_rt_msgs
 match message setup
 policy-map type inspect h323 my_h323_policy
!
class type inspect h323 my_h323_rt_msgs
 rate-limit 16
!
policy-map type inspect my_voice_policy
 class type inspect my_voice_class
 inspect
 service-policy h323 my_h323_policy
!

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Cisco IOS security commands

Cisco IOS Security Command Reference

Overview of the H.323 Standard

"Information About H.323" section in H.323 Overview module

Description of H.323 and RAS support in Cisco IOS firewall

H.323 RAS Support in Cisco IOS Firewall module

Overview of class maps and policy maps for zone-based policy firewalls

"Class Maps and Policy Maps for Zone-Based Policy Firewalls" section in the Zone-Based Policy Firewall module

Description of how to configure a zone-based policy firewall

"How to Configure Zone-Based Policy Firewall" section in the Zone-Based Policy Firewall module

Standards

Standard

Title

ITU-T H.225.0

Call signalling protocols and media stream packetization for packet-based multimedia communication systems

ITU-T H.245

Control protocol for multimedia communication

ITU-T H.323 (H.323 Version 4 and earlier)

Packet-based multimedia communications systems

ITU-T H.450

Supplementary services for multimedia

MIBs

MIB

MIBs Link

No new or modified MIBs are supported.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Cisco IOS Firewall-H.323 V3 V4 Support

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 3 Feature Information for Cisco IOS Firewall - H.323 V3/V4 Support

Feature Name

Releases

Feature Information

Cisco IOS Firewall--H.323 V3/V4 Support

12.4(20)T

This feature introduces support for a range of H.323 Version 3 and Version 4 features and support for a rate-limiting mechanism to monitor call attempt rate and call aggregation.

The following commands were introduced or modified: class-map type inspect, class type inspect, match message, match protocol h323-annexe, match protocol h323-nxg, match protocol (zone), policy-map type inspect, rate-limit (firewall), service-policy (policy-map), service-policy type inspect.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2012 Cisco Systems, Inc. All rights reserved.