Uri Dialing Via Dns For Incoming Calls - Cisco TelePresence Administrator's Manual

configure the DNS servers
n
create a DNS zone and set up associated search rules that use the Pattern string and Pattern type fields
n
to define the aliases that will trigger a DNS query
For example, rules with:
a Pattern string of .*@.* and a Pattern type of Regex will query DNS for all aliases in the form of typical
n
URI addresses
a Pattern string of (?!.*@example.com$).* and a Pattern type of Regex will query DNS for all aliases in
n
the form of typical URI addresses except those for the domain example.com
To set up further filters, configure extra search rules that target the same DNS zone. You do not need to
create new DNS zones for each rule unless you want to filter based on the protocol (SIP or H.323) or use
different hop counts.
Note: you are not recommended to configure search rules with a Mode of Any alias for DNS zones. This will
result in DNS always being queried for all aliases, including those that may be locally registered and those
that are not in the form of URI addresses.

URI dialing via DNS for incoming calls

DNS record types
The ability of the VCS to receive incoming calls made using URI dialing via DNS relies on the presence of
DNS records for each domain the VCS is hosting.
These records can be of various types including:
A records, which provide the IPv4 address of the VCS
n
AAAA records, which provide the IPv6 address of the VCS
n
Service (SRV) records, which specify the FQDN of the VCS and the port on it to be queried for a particular
n
protocol and transport type.
NAPTR records, which specify SRV record and transport preferences for a SIP domain.
n
You must provide an SRV or NAPTR record for each combination of domain hosted and protocol and
transport type enabled on the VCS.
Incoming call process
When an incoming call has been placed using URI dialing via DNS, the VCS will have been located by the
calling system using one of the DNS record lookups described above. The VCS will receive the request
containing the dialed URI in the form user@example.com. This will appear as coming from the Default Zone.
The VCS will then search for the URI in accordance with its normal
search transforms, Call Policy and FindMe policy, then searching its Local Zone and other configured zones,
in order of search rule priority.
SRV record format
The format of SRV records is defined by
_Service._Proto.Name TTL Class SRV Priority Weight Port Target
For the VCS, these are as follows:
Cisco VCS Administrator Guide (X7.2)
used by the VCS for DNS queries
RFC 2782 as:
Dial plan and call processing
call routing process, applying any pre-
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