Cisco Cisco TelePresence Video Communication Server Expressway
Appendix 5 – Configuring endpoints to work with a VCS cluster
Cisco VCS Deployment Guide: Cluster creation and maintenance (Cisco VCS X7.1)
Page 52 of 69
Appendix 5 – Configuring endpoints to work
with a VCS cluster
with a VCS cluster
When configuring endpoints it is desirable for them to know about all the VCS peers in a cluster, so
that at initial registration or later, if they lose connection to their VCS peer, they have the ability to
register with and use another peer in the VCS cluster.
that at initial registration or later, if they lose connection to their VCS peer, they have the ability to
register with and use another peer in the VCS cluster.
SIP and H.323 endpoints behave differently – the following sections show the methods that can be
used, and order them in preferred order.
used, and order them in preferred order.
For additional details about DNS SRV and round-robin DNS see the URI dialling section in the VCS
Administrator Guide.
Administrator Guide.
H.323 endpoints
The options below are listed in preference order for providing resilience of connectivity of endpoints to
a cluster of VCSs where 1 or more VCS cluster peers become inaccessible. The choice of option will
depend on what functionality the endpoint you are using supports.
a cluster of VCSs where 1 or more VCS cluster peers become inaccessible. The choice of option will
depend on what functionality the endpoint you are using supports.
Option 1 – DNS SRV (preferred)
To use this option, there must be a DNS SRV record available for the DNS name of the VCS cluster
that defines an equal weighting and priority for each cluster peer.
that defines an equal weighting and priority for each cluster peer.
On each H.323 endpoint, configure the Gatekeeper Settings as:
Discovery = Manual
IP Address = DNS name of the VCS cluster
If the endpoint supports DNS SRV, on startup the endpoint issues a DNS SRV request and receives a
DNS SRV record back defining an equal weighting and priority for each cluster peer. It may also
receive a list of lower priority entries pointing at a fallback cluster.
DNS SRV record back defining an equal weighting and priority for each cluster peer. It may also
receive a list of lower priority entries pointing at a fallback cluster.
The endpoint then tries to register with a relevant cluster peer (having taken into account the priority /
weightings). If that peer is not available, the endpoint will try and register to another listed peer at the
same priority, or if all peers at that priority have been tried, a peer at the next lower (higher numbered)
priority.
weightings). If that peer is not available, the endpoint will try and register to another listed peer at the
same priority, or if all peers at that priority have been tried, a peer at the next lower (higher numbered)
priority.
This will be repeated until the endpoint can register with a VCS. On registering with the VCS, the VCS
will respond with the H.323 “Alternate Gatekeepers” list containing the list of VCS cluster peer
members.
will respond with the H.323 “Alternate Gatekeepers” list containing the list of VCS cluster peer
members.
The endpoint will continue to use the first VCS that it registered to for re-registrations and for calls. If it
ever loses connection to its VCS then it will select an “Alternate Gatekeeper” from the list it was
supplied with.
ever loses connection to its VCS then it will select an “Alternate Gatekeeper” from the list it was
supplied with.
DNS SRV cache timeout should be set to a fairly long time (e.g. 24 hours) to minimize DNS traffic.
Option 2 – DNS Round-Robin (2nd choice)
To use this option, there must be a DNS A-record available for the DNS name of the VCS cluster that
supplies a round-robin list of IP addresses.
supplies a round-robin list of IP addresses.
On each H.323 endpoint configure the Gatekeeper Settings as:
Discovery = Manual
IP Address = DNS name of the VCS cluster