Cisco Cisco Expressway

Note:

We strongly recommend that you create internal DNS records, for both forward and reverse lookups, for all Unified

Communications nodes used with Mobile and Remote Access. This should allow Expressway-C to find the nodes when
IP addresses are used instead of FQDNs.

DNS SRV Configuration for Legacy Video Conferencing Deployments

The format of DNS SRV queries for sip (RFC 3263) and H.323 used by Expressway are:

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_sips._tcp.<fully.qualified.domain>

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_sip._tcp.<fully.qualified.domain>

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_sip._udp.<fully.qualified.domain> - not recommended for video calls, only use for audio-only calls

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_h323ls._udp.<fully.qualified.domain> - for UDP location (RAS) signaling, such as LRQ

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_h323cs._tcp.<fully.qualified.domain> - for H.323 call signaling

The format of DNS SRV queries for sip (RFC 3263) and H.323 typically used by an endpoint are:

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_sips._tcp.<fully.qualified.domain>

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_sip._tcp.<fully.qualified.domain>

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_sip._udp.<fully.qualified.domain> - not recommended for video calls, only use for audio-only calls

■

_h323ls._udp.<fully.qualified.domain> - for UDP location (RAS) signaling, such as LRQ

■

_h323cs._tcp.<fully.qualified.domain> - for H.323 call signaling

Note that UDP is not a recommended transport medium for video signaling; SIP messaging for video system is too large
to be reliably carried on datagram-based (rather than stream-based) transports.

The Expressway Cluster name (configured on the System > Clustering page) should be the <fully.qualified.domain>
specified in the DNS SRV records that point to the Expressway cluster.

Example

DNS SRV records for 2 peers of an Expressway-E cluster for example.com

where:

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FQDN of Expressway-E peer 1: expe1.example.com

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FQDN of Expressway-E peer 2: expe2.example.com

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FQDN of Expressway-E cluster: example.com

_sips._tcp.example.com. 86400 IN SRV 1 1 5061 expe1.example.com.

_sips._tcp.example.com. 86400 IN SRV 1 1 5061 expe2.example.com.

_sip._tcp.example.com. 86400 IN SRV 1 1 5060 expe1.example.com.

_sip._tcp.example.com. 86400 IN SRV 1 1 5060 expe2.example.com.

_h323ls._udp.example.com. 86400 IN SRV 1 1 1719 expe1.example.com.

_h323ls._udp.example.com. 86400 IN SRV 1 1 1719 expe2.example.com.

_h323cs._tcp.example.com. 86400 IN SRV 1 1 1720 expe1.example.com.

_h323cs._tcp.example.com. 86400 IN SRV 1 1 1720 expe2.example.com.

Note that:

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Priorities are all the same. Only use different priorities if you have different clusters allowing failover from one
primary cluster to another (secondary) cluster. In that case the primary cluster’s peers should have one value and
the other (secondary) cluster’s peers a (larger) value.

■

Weights should be the same – so that there is equal use of each peer.

Cisco Expressway Cluster Creation and Maintenance Deployment Guide