Cisco Cisco Expressway
Appendix 7: Configure Endpoints to Work With a Cluster
When configuring endpoints it is desirable for them to know about all the Expressway peers in a cluster, so that at
initial registration or later, if they lose connection to their Expressway peer, they have the ability to register with and
use another peer in the Expressway cluster.
initial registration or later, if they lose connection to their Expressway peer, they have the ability to register with and
use another peer in the Expressway cluster.
For additional details about DNS SRV and round-robin DNS see the URI dialing section in Expressway Administrator
Guide.
Guide.
.
SIP Endpoints
The options below are listed in preference order for providing resilience of connectivity of endpoints to a cluster of
Expressways where 1 or more Expressway cluster peers become inaccessible. The choice of option will depend on
what functionality the endpoint you are using supports.
Expressways where 1 or more Expressway cluster peers become inaccessible. The choice of option will depend on
what functionality the endpoint you are using supports.
Option 1 – SIP Outbound (preferred)
SIP outbound allows an endpoint to be configured to register to 2 or more Expressway peers simultaneously. The
benefit of this is that if the connection between one peer and the endpoint gets broken, then a connection from the
endpoint to the other peer remains. With the endpoint registering to both peers simultaneously, there is no break in
service while the endpoint realizes that its registration has failed, before it registers to a different peer. Thus, at no
time is the endpoint unreachable.
benefit of this is that if the connection between one peer and the endpoint gets broken, then a connection from the
endpoint to the other peer remains. With the endpoint registering to both peers simultaneously, there is no break in
service while the endpoint realizes that its registration has failed, before it registers to a different peer. Thus, at no
time is the endpoint unreachable.
Configuration of SIP outbound is endpoint specific, but typically will be:
■
Proxy 1
—
Server discovery = Manual
—
Server Address =
DNS name of cluster peer or
IP address of cluster peer
IP address of cluster peer
■
Proxy 2
—
Server discovery = Manual
—
Server Address =
DNS name of a different cluster peer or
IP address of a different cluster peer
IP address of a different cluster peer
■
Outbound = On
Option 2 – DNS SRV (2nd choice)
To use this option, there must be a DNS SRV record available for the DNS name of the Expressway cluster that
defines an equal weighting and priority for each cluster peer.
defines an equal weighting and priority for each cluster peer.
On each SIP endpoint configure the SIP Settings as:
■
Server discovery = Manual
■
Server Address = DNS name of the Expressway 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.
back defining an equal weighting and priority for each cluster peer.
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 priority.
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 priority.
This will be repeated until the endpoint can register with a Expressway.
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Cisco Expressway Cluster Creation and Maintenance Deployment Guide
Appendix 7: Configure Endpoints to Work With a Cluster