Cisco Cisco Expressway Manual De Manutenção
URI Dialing via DNS for Incoming Calls
DNS record types
The ability of the Expressway to receive incoming calls (and other messages, such as registrations) made using URI
dialing via DNS relies on the presence of DNS records for each domain the Expressway is hosting.
dialing via DNS relies on the presence of DNS records for each domain the Expressway is hosting.
These records can be of various types including:
■
A records, which provide the IPv4 address of the Expressway
■
AAAA records, which provide the IPv6 address of the Expressway
■
Service (SRV) records, which specify the FQDN of the Expressway and the port on it to be queried for a
particular protocol and transport type.
particular protocol and transport type.
■
NAPTR records, which specify SRV record and transport preferences for a SIP domain.
You must provide an SRV or NAPTR record for each combination of domain hosted and protocol and transport type
enabled on the Expressway.
enabled on the Expressway.
Incoming call process
When an incoming call has been placed using URI dialing via DNS, the Expressway will have been located by the
calling system using one of the DNS record lookups described above. The Expressway will receive the request
containing the dialed URI in the form user@example.com. This will appear as coming from the Default Zone. The
Expressway will then search for the URI in accordance with its normal
calling system using one of the DNS record lookups described above. The Expressway will receive the request
containing the dialed URI in the form user@example.com. This will appear as coming from the Default Zone. The
Expressway will then search for the URI in accordance with its normal
, applying any pre-search
transforms, Call Policy and FindMe policy, then searching its Local Zone and other configured zones, in order of
search rule priority.
search rule priority.
SRV record format
_Service._Proto.Name TTL Class SRV Priority Weight Port Target
For the Expressway, these are as follows:
■
_Service
and
_Proto
will be different for H.323 and SIP, and will depend on the protocol and transport type
being used
■
Name
is the domain in the URI that the Expressway is hosting (such as
example.com
)
■
Port
is the IP port on the Expressway that has been configured to listen for that particular service and protocol
combination
■
Target
is the FQDN of the Expressway.
Configuring H.323 SRV Records
defines the procedures for using DNS to locate gatekeepers and endpoints and
for resolving H.323 URL aliases. It also defines parameters for use with the H.323 URL.
The Expressway supports the location, call and registration service types of SRV record as defined by this Annex.
Location service SRV records
Location records are required for gatekeepers that route calls to the Expressway. For each domain hosted by the
Expressway, you should configure a location service SRV record as follows:
Expressway, you should configure a location service SRV record as follows:
■
_Service
is
_h323ls
■
_Proto
is
_udp
■
Port is the port number that has been configured from Configuration > Protocols > H.323 as the Registration
UDP port
UDP port
194
Cisco Expressway Administrator Guide
Dial Plan and Call Processing