Cisco Cisco IOS Software Release 12.4(2)XB6

Before you configure VRF-aware H.323 and SIP for voice gateways, you must do the following: 

Be sure that you have the correct platform to support this feature. VRF-aware H.323 and SIP is 
supported on the following platforms:

For TDM-to-IP calls—Cisco 2600XM, 2691, 3700, 2800, 2801, 3800, 7200, AS5350XM, and 
AS5400XM

For IP-to-IP calls— Cisco 2600XM, 2691, 3700, 2800, 2801, 3800, 7301, 7200, AS5350XM, 
and AS5400XM

VRF support requires Cisco Express Forwarding switching to be enabled on the router. The above 
listed platforms all support Cisco Express Forwarding switching. However, customer edge (CE) or 
provider edge (PE) routers configured as voice gateways might require installation of additional 
voice interface cards and DSP modules.

Configuration restrictions for VRF-aware H.323 and SIP for voice gateways are as follows: 

SIP proxy and registrar must be in the same VRF.

The following call types are not supported for voice VRF:

An IP-to-IP gateway and gatekeeper configured on the same router.

An IP-to-IP gateway with a VRF configured on one call leg and not on another call leg.

An IP-to-IP gateway with one VRF configured for the H.323 call leg and a different VRF configured 
for the SIP call leg.

Skinny Client Control Protocol (SCCP) on Cisco SRST routers.

SCCP on Cisco Unified Communications Manager Express (Cisco Unified CME) routers.

SIP on Cisco Unified CME routers.

Call that involve transcoding, including both internal and external transcoders.

SIP calls support both TCP and UDP signaling. However, for H.323 calls, only TCP is supported. 
H.323 UDP signaling is not supported.

The following features are not supported by VRF-aware H.323 and SIP:

Call-fallback and RSVP features.

H.323 Annex E calls.

AAA and DNS components in voice-capable access routers. These routers communicate with AAA 
and DNS using the default routing table.