Cisco H.323 VC-289 - Manual (Page 14)

Configuring H.323 Gatekeepers and Proxies
H.323 Prerequisite Tasks and Restrictions
VC-302
Cisco IOS Voice, Video, and Fax Configuration Guide
Application-specific routing is simple. When the proxy receives outbound traffic, it directs traffic to an
interface that is connected directly to the QoS network. The proxy does not send the traffic using an
interface that is specified for the regular routing protocol. Similarly, inbound traffic from other proxies
is received on the interface that is connected to the QoS network. This is true if all these other proxies
around the QoS network use ASR in a consistent fashion. ASR then ensures that ordinary traffic is not
routed into the QoS network by mistake.
Implementation of ASR ensures the following:
• Each time a connection is established with another proxy, the proxy automatically installs a host
route pointing at the interface designated for ASR.
• The proxy is configured to use a loopback interface address. The proxy address is visible to both the
ASR interface and all regular interfaces, but there are no routes established between the loopback
interface and the ASR interface. This ensures that no non-H.323 traffic is routed through the ASR
interface.
Note ASR is not supported on Frame Relay or ATM interfaces for the Cisco MC3810 platform.
H.323 Prerequisite Tasks and Restrictions
This section contains prerequisite tasks and restrictions for configuring H.323 gatekeepers and proxies.
Redundant H.323 Zone Support
Redundant H.323 zone support has the following restrictions and limitations:
• The gateway can register with only one gatekeeper at any given time.
• Only E.164 address resolution is supported.
• Because the gateway can register with only one gatekeeper at a time, redundant H.323 zone support
provides only redundancy and does not provide any load balancing.
• Although redundant H.323 zone support allows you to configure alternate gatekeepers, it will not
insert information in the alternate gatekeeper field of some RAS messages.
Gatekeeper-to-Gatekeeper Redundancy and Load-Sharing Mechanism
The gatekeeper-to-gatekeeper redundancy and load-sharing mechanism has the following restrictions
and limitations:
• The gatekeeper-to-gatekeeper redundancy and load-sharing mechanism requires the Cisco H.323
VoIP Gatekeeper for Cisco Access Platforms feature.
• The order in which LRQs are sent to the gatekeepers is based on the order in which the gatekeepers
are listed. You cannot specify a priority number for a gatekeeper.
• Regardless of the order in which the LRQs are sent, the gateway will still use the first gatekeeper
that sends an LCF.
• The settings for delay between LRQs and the LRQ window are global and cannot be set on a
per-zone or technology-prefix basis.