Cisco Cisco Expressway
Appendix 2: Extended Lync Deployments
Clustered Gateway
When this document refers to a Gateway Expressway, a cluster of Expressways can also be used. The operation is
functionally the same, but there is more capacity available.
functionally the same, but there is more capacity available.
Calls from Lync FE will typically arrive at a single Expressway in the cluster because Lync FE will use the static
domain route; the route resolves to a single FQDN for TLS connectivity, or to a single IP address for TCP connectivity.
domain route; the route resolves to a single FQDN for TLS connectivity, or to a single IP address for TCP connectivity.
If you use a DNS A record to to map the peers' IP addresses to the FQDN of the cluster, the DNS server typically
returns the IP addresses in a different order each time the Lync Server queries DNS (round-robin). Lync FE chooses
one of the returned addresses, based on its own logic (outside of this document's scope).
returns the IP addresses in a different order each time the Lync Server queries DNS (round-robin). Lync FE chooses
one of the returned addresses, based on its own logic (outside of this document's scope).
Lync Environments
Lync environments have a number of building blocks, and so they may be constructed in many ways. A full scale Lync
deployment is likely to use Lync Director, Hardware Load Balancers (HLBs), Front End Servers in enterprise pools, and
a redundant AD server.
deployment is likely to use Lync Director, Hardware Load Balancers (HLBs), Front End Servers in enterprise pools, and
a redundant AD server.
For Lync installations, Microsoft recommend that DNS may be used in place of hardware load balancing for routing
SIP traffic. Microsoft guidance can be found at
SIP traffic. Microsoft guidance can be found at
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Cisco Expressway with Microsoft Lync Deployment Guide
Appendix 2: Extended Lync Deployments