Cisco Cisco Expressway Maintenance Manual
searching local and external zones in priority order).From this point, as it is now searching for a SIP/H.323
URI, the process for URI dialing is followed.
URI, the process for URI dialing is followed.
In this example, we want to call Fred at Example Corp. Fred’s endpoint is actually registered with the URI
fred@example.com
fred@example.com
, but to make it easier to contact him his system administrator has configured a DNS
NAPTR record mapping this alias to his E.164 number: +44123456789.
We know that the NAPTR record for example.com uses the DNS domain of e164.arpa.
1. We create an ENUM zone on our local Expressway with a DNS suffix of e164.arpa.
2. We configure a search rule with a Pattern match mode of Any alias, and set the Target to the ENUM
zone. This means that ENUM will always be queried regardless of the format of the alias being searched
for.
for.
3. We dial 44123456789 from our endpoint.
4. The Expressway initiates a search for a registration of 44123456789 and the search rule of Any alias
means the ENUM zone is queried. (Note that other higher priority searches could potentially match the
number first.)
number first.)
5. Because the zone being queried is an ENUM zone, the Expressway is automatically triggered to transform
the number into an ENUM domain as follows:
a. The digits are reversed and separated by a dot: 9.8.7.6.5.4.3.2.1.4.4.
b. The DNS suffix configured for this ENUM zone, e164.arpa, is appended. This results in a
b. The DNS suffix configured for this ENUM zone, e164.arpa, is appended. This results in a
transformed domain of 9.8.7.6.5.4.3.2.1.4.4.e164.arpa.
6. DNS is then queried for that ENUM domain.
7. The DNS server finds the domain and returns the information in the associated NAPTR record. This tells
the Expressway that the E.164 number we have dialed is mapped to the SIP URI of
fred@example.com
fred@example.com
.
8. The Expressway then starts another search, this time for fred@example.com. From this point the
process for URI dialing is followed, and results in the call being forwarded to Fred’s endpoint.
Configuring zones and search rules for ENUM dialing
To support ENUM dialing, you must configure an ENUM zone and related search rules for each ENUM
service used by remote endpoints.
service used by remote endpoints.
Adding and configuring ENUM zones
To set up an ENUM zone:
1. Go to
Configuration > Zones > Zones
.
2. Click New. You are taken to the
Create zone
page.
3. Enter a Name for the zone and select a Type of ENUM.
4. Configure the ENUM zone settings as follows:
Field
Guidelines
Hop count
specified for an ENUM zone is applied in the same manner as hop counts for
other zone types. The currently applicable hop count is maintained when the Expressway
initiates a new search process for the alias returned by the DNS lookup.
initiates a new search process for the alias returned by the DNS lookup.
Cisco Expressway Administrator Guide (X8.2)
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Dial plan and call processing
About ENUM dialing