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This feature module describes the Gateway Support for Alternate Gatekeeper feature. It includes information on the benefits of the new feature, supported platforms, related documents, and so forth.
The Alternate Gatekeeper feature provides redundancy for a gatekeeper in a system where gatekeepers are used. This enhancement allows a gateway to use up to two alternate gatekeepers as a backup in the case of a primary gatekeeper failure.
A gatekeeper manages H.323 endpoints in a consistent manner, allowing them to register with the gateway and to locate another gatekeeper. The gatekeeper provides logic variables for proxies or gateways in a call path, to provide connectivity with the public switched telephone network (PSTN), to improve Quality of Service (QoS), and to enforce security policies. Multiple gatekeepers may be configured to communicate with one another, either by integrating their addressing into Domain Naming System (DNS) or using Cisco IOS configuration options.
This feature allows for up to two alternate gatekeepers to be used in the case that the primary gatekeeper becomes unresponsive.
Configuring H.323 VoIP Gatekeeper for Cisco Access Platforms
The Alternate Gatekeeper feature is available on Cisco platforms that support H.323 gateway functionality. This includes:
No new or modified standards are supported by this feature.
No new or modified MIBs are supported by this feature.
For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
No new or modified RFCs are supported by this feature.
| Step | Command | Purpose | ||
|---|---|---|---|---|
| Router(config)#configure interface | Enter interface configuration mode. | ||
| Router(config-if)#interface Ethernet 0/1 | Configure this Ethernet interface. | ||
| Router(config-if)# | Identify the IP address of the Ethernet interface. | ||
| Router(config-if)# | Enter the VoIP interface command to configure the alternate gatekeeper. | ||
| Router(config-if)# | Identify the gatekeeper and set the attributes. See the "Command Reference" section for more information. | ||
| Router(config-if)# | Identify the alternate gatekeeper. | ||
| Router(config-if)# | Identify the H.323 ID of a particular H.323 end-point, which is the gateway in this case. | ||
| Router(config-if)# end | Exit interface configuration mode. |
Step 1 Enter the show gate command to see that there is an alternate gatekeeper configured.
Alternate Gatekeeper List
priority 126 id GK1 ipaddr 172.18.193.61 1719
priority 127 id GK2 ipaddr 172.18.193.63 1719
In the following example, the primary and secondary gatekeepers are configured with the priority option. The priority range is 1 through 127. The first gatekeeper has been configured as priority 120; the second gatekeeper has not been configured, so it remains at the default setting of 127.
interface Ethernet 0/1
ip address 172.18.193.59 255.255.255.0
h323-gateway voip interface
h323-gateway voip id GK1 ipaddr 172.18.193.65 1719 priority 120
h323-gateway voip id GK1 ipaddr 172.18.193.65 1719
h323-gateway voip h323-id cisco2
This section documents the command you use to configure an alternate gatekeeper.
To configure an additional gatekeeper to be used when the primary gatekeeper becomes unresponsive, use the h323-gateway voip interface command. To disable, use the no form of this command.
h323-gateway voip gatekeeper-ID ip-address priority numbergatekeeper-ID | The name of the gatekeeper. |
ip-address | The IP address of the gatekeeper. |
priority number | The priority of this gatekeeper. Range is 1 through 127, and the default value is 127. |
The default value for priority is 127.
Interface configuration mode.
| Release | Modification |
|---|---|
12.0(7)T | This command was introduced. |
You can configure up to two alternate gatekeepers.
The IP address of the gatekeeper does not have to be explicit; you can also use the multicast option. Multicasting saves bandwidth by forcing the network to replicate packets only when necessary. The multicast option, shown below, notifies every gatekeeper in the local area network (LAN) using a universal address, 224.0.1.41.
h323-gateway voip id GK1 multicast
h323-gateway voip id GK2 ipaddr 172.18.193.65 1719
The following example shows two gatekeepers configured with the same priority value, but the first gatekeeper configured will be the first one used. 1719 is the UDP port number that is universally defined by H.323 standards for communicating to the gatekeeper from an endpoint.
priority 127 id GK1 ipaddr 172.18.193.61 1719
priority 127 id GK2 ipaddr 172.18.193.63 1719
AAA---Authentication, Authorization, and Accounting. AAA is a suite of network security services that provide the primary framework through which access control can be set up on your Cisco router or access server.
ANI---Answer number indication. The calling number (number of calling party).
ARQ---Admission request.
CAS---Channel associated signaling.
dial peer---An addressable call endpoint. In Voice over IP (VoIP), there are two types of dial peers: POTS and VoIP.
endpoint---An H.323 terminal or gateway. An endpoint can call and be called. It generates or terminates the information stream, or both.
gatekeeper---A gatekeeper maintains a registry of devices in the multimedia network. The devices register with the gatekeeper at startup, and request admission to a call from the gatekeeper.
The gatekeeper is an H.323 entity on the LAN that provides address translation and control access to the LAN for H.323 terminals and gateways. The gatekeeper may provide other services to the H.323 terminals and gateways, such as bandwidth management and locating gateways.
gateway---A gateway allows H.323 terminals to communicate with non-H.323 terminals by converting protocols. A gateway is the point at which a circuit-switched call is encoded and repackaged into IP packets.
A H.323 gateway is an endpoint on the LAN that provides real-time, two-way communications between H.323 terminals on the LAN and other ITU-T terminals in the WAN, or to another H.323 gateway.
H.323---An International Telecommunication Union (ITU-T) standard that describes packet-based video, audio, and data conferencing. H.323 is an umbrella standard that describes the architecture of the conferencing system, and refers to a set of other standards (H.245, H.225.0, and Q.931) to describe its actual protocol.
H.323 RAS---Registration, admission, and status. The RAS signaling function performs registration, admissions, bandwidth changes, status, and disengage procedures between the VoIP gateway and the gatekeeper.
LRQ---Location request.
node---An H.323 entity that uses RAS to communicate with the gatekeeper. For example, an endpoint such as a terminal, proxy, or gateway.
POTS---Plain old telephone service. Basic telephone service supplying standard single-line telephones, telephone lines, and access to the PSTN.
PSTN---Public switched telephone network. PSTN refers to the local telephone company.
QoS---Quality of service, which refers to the measure of service quality provided to the user.
RAS---Registration, admission, and status protocol. This is the protocol that is used between endpoints and the gatekeeper to perform management functions.
RBS---Robbed bit signaling
RRQ---Registration request.
VoIP---Voice over IP. The ability to carry normal telephone-style voice over an IP-based internet with POTS-like functionality, reliability, and voice quality. VoIP is a blanket term that generally refers to Cisco's standards-based (H.323, and so on.) approach to IP voice traffic.
Posted: Fri Dec 10 18:50:36 PST 1999
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