The voice solution supports up to eight concurrent VPGs in a router. Each VPG is connected to a PGC over its own PGCP connection. One VPG can connect to one PGC at the same time. Multiple VPGs can share a single service PIC. A single VPG cannot span more than one service PIC.
Creating multiple VPGs allows you to deploy different policy and quality of service (QoS) characteristics in your network. It also allows you to scale your infrastructure by using multiple MultiServices PICs to control voice traffic.
Figure 12 shows a topology with multiple VPGs and PGCs. This topology allows one VPG and one MultiServices PIC to continue handling gate requests and forwarding packets on open gates even when the other PIC fails.
Figure 12: Topology with Multiple VPGs and PGCs
You can have multiple PGCs configured for one VPG. When a VPG begins running on the router, it attempts to set up a connection to the first configured PGC. Each VPG can have one active PGC and one or more standby PGCs. In case of a PGC failure or in case of the PGC sending instructions to the VPG, the VPG can switch to another PGC. Figure 13 shows an active and standby PGC connected to VPG 2.
Figure 13: Active and Standby PGCs
If the PGCP connection between the VPG and the PGC is lost, the VPG attempts to reconnect to the PGC. If the VPG cannot reconnect to the PGC, it traverses its list of PGCs until it successfully connects to one of the PGCs.
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