Cisco Cisco Expressway
The Lync Server selects one IP address to use, based on its own logic (outside of this document's scope). If
the TTL of the record has not expired when the Lync Server makes a new DNS query, the Lync Server will
use the same IP address it used the previous time. If the Lync Server cannot connect to the IP address it
selected, it will try another of the IP addresses returned by the DNS server.
the TTL of the record has not expired when the Lync Server makes a new DNS query, the Lync Server will
use the same IP address it used the previous time. If the Lync Server cannot connect to the IP address it
selected, it will try another of the IP addresses returned by the DNS server.
Why add a “Lync gateway” Expressway?
The “Lync gateway” Expressway is an interface between an existing working video network and the
Microsoft Lync environment. Using this gateway minimizes the changes that need to be made in the video
network so as to introduce as few artifacts as possible when adding Lync interoperability to the video
network.
Microsoft Lync environment. Using this gateway minimizes the changes that need to be made in the video
network so as to introduce as few artifacts as possible when adding Lync interoperability to the video
network.
Having dedicated Expressways for this “Lync gateway” operation limits the number of Expressways for
which the Microsoft Interoperability option key needs to be purchased and enabled.
which the Microsoft Interoperability option key needs to be purchased and enabled.
Lync Server can only send calls to a single FQDN (though this may have a round robin DNS address to
support a cluster of Expressways for resilience) for calls via a static domain route defined in Lync Server.
support a cluster of Expressways for resilience) for calls via a static domain route defined in Lync Server.
Lync Server will only accept messages received from peers that it has been configured to trust. Having a
dedicated “Lync gateway” Expressway or Expressway cluster also limits the number of trusted devices that
need to be configured in Lync, as every device that sends SIP messages to Lync Server needs to be
explicitly listed as a trusted host in Lync Server.
dedicated “Lync gateway” Expressway or Expressway cluster also limits the number of trusted devices that
need to be configured in Lync, as every device that sends SIP messages to Lync Server needs to be
explicitly listed as a trusted host in Lync Server.
Multiple Lync domains and relationships to multiple Lync gateway Expressway
You can integrate Cisco collaboration infrastructure with more than one Lync domain if required, but you need
to set up a "Lync gateway" Expressway into each Lync domain. Wherever you put a single Expressway as a
gateway, you could use a cluster instead.
to set up a "Lync gateway" Expressway into each Lync domain. Wherever you put a single Expressway as a
gateway, you could use a cluster instead.
Take care when you design your deployment that you don't have more than one gateway per Lync domain, or
more than one Lync domain per gateway. See the diagram below which shows the following different options:
more than one Lync domain per gateway. See the diagram below which shows the following different options:
1. This option is used in this document; there is one gateway Expressway (or cluster) into a single Lync
domain.
2. It is possible to configure multiple Lync domains, provided you have an independent gateway serving
each. This option is not exhaustively tested, nor is it described in this document.
3. You cannot configure multiple Lync domains with only one Lync gateway Expressway serving all of them.
4. You should avoid configuring multiple gateways to serve one Lync domain. With this deployment, calls
from one video endpoint to another video endpoint that is called via its Lync domain will get routed via Lync
rather than directly through the collaboration infrastructure; users could lose duo video, far end camera
control, and possibly encryption and video quality.
rather than directly through the collaboration infrastructure; users could lose duo video, far end camera
control, and possibly encryption and video quality.
Microsoft Lync and Cisco Expressway Deployment Guide (X8.5)
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Introduction