Cisco Cisco Expressway Maintenance Manual
Note:
ENUM dialing relies on the presence of relevant DNS NAPTR records for the ENUM domain being queried. These
are the responsibility of the administrator of that domain.
ENUM Dialing Process
When the Expressway attempts to locate a destination endpoint using ENUM, the general process is as follows:
1.
The user dials the E.164 number from their endpoint.
2.
The Expressway converts the E.164 number into an ENUM domain as follows:
a.
The digits are reversed and separated by a dot.
b.
The name of the domain that is hosting the NAPTR records for that E.164 number is added as a suffix.
3.
DNS is then queried for the resulting ENUM domain.
4.
If a NAPTR record exists for that ENUM domain, this will advise how the number should be converted into one
(or possibly more) H.323/SIP URIs.
(or possibly more) H.323/SIP URIs.
5.
The Expressway begins the search again, this time for the converted URI as per the URI dialing process. Note
that this is considered to be a completely new search, and so pre-search transforms and Call Policy will
therefore apply.
that this is considered to be a completely new search, and so pre-search transforms and Call Policy will
therefore apply.
Enabling ENUM Dialing
ENUM dialing is enabled separately for incoming and outgoing calls.
Outgoing calls
To allow outgoing calls to other endpoints using ENUM, you must:
■
configure at least one ENUM zone, and
■
configure at least one DNS Server
section.
Incoming calls
To enable endpoints in your enterprise to receive incoming calls from other endpoints via ENUM dialing, you must
configure a DNS NAPTR record mapping your endpoints’ E.164 numbers to their SIP/H.323 URIs. See the
configure a DNS NAPTR record mapping your endpoints’ E.164 numbers to their SIP/H.323 URIs. See the
Note:
if an ENUM zone and a DNS server have not been configured on the local Expressway, calls made using ENUM
dialing could still be placed if the local Expressway is neighbored with another Expressway that has been
appropriately configured for ENUM dialing. Any ENUM dialed calls will go via the neighbor. This configuration is useful
if you want all ENUM dialing from your enterprise to be configured on one particular system.
appropriately configured for ENUM dialing. Any ENUM dialed calls will go via the neighbor. This configuration is useful
if you want all ENUM dialing from your enterprise to be configured on one particular system.
ENUM Dialing for Outgoing Calls
For a local endpoint to be able to dial another endpoint using ENUM via your Expressway, the following conditions
must be met:
must be met:
■
There must be a NAPTR record available in DNS that maps the called endpoint’s E.164 number to its URI. It is
the responsibility of the administrator of the enterprise to which the called endpoint belongs to provide this
record, and they will only make it available if they want the endpoints in their enterprise to be contactable via
ENUM dialing.
the responsibility of the administrator of the enterprise to which the called endpoint belongs to provide this
record, and they will only make it available if they want the endpoints in their enterprise to be contactable via
ENUM dialing.
■
on your local Expressway. This ENUM zone must have a DNS Suffix that is
the same as the domain where the NAPTR record for the called endpoint is held.
■
that it can query for the
NAPTR record (and if necessary any resulting URI).
After the ENUM process has returned one or more URIs, a new search will begin for each of these URIs in accordance
with the URI dialing process. You also need to configure a DNS zone if they are to be located using a DNS lookup.
with the URI dialing process. You also need to configure a DNS zone if they are to be located using a DNS lookup.
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Cisco Expressway Administrator Guide