'e164-pattern-map' and 'server-group' command on Cisco IOS

Two commands: 'e164-pattern-map' (added from IOS 15.2) and 'server-group' (added from IOS 15.4) makes Voice Gateway/CUBE config dial-peers config very clean.

With e164-pattern-map, the digits to be matched can be groped together. So no need for multiple dial-peers (with just the changing destination-pattern). 

With server-group, all the session target (session target ipv4:x.x.x.x) can be grouped together. So no need for multiple dial-peers with just the changing session target ipv4: is required. 

Here is an example which will make things more clear:


voice class e164-pattern-map 10
​ e164 911
 e164 9[2-9]..[2-9]......
 e164 91[2-9]..[2-9]......
 e164 9[^1]T
 description OUTBOUND_CALLS

voice class e164-pattern-map 20
 e164 +1416555[12]...
 description INBOUND_CALLS

voice class server-group 10
 ipv4 140.1.4.5 preference 1
 ipv4 140.1.5.5 preference 2
 description to PSTN_SIP_PROVIDER
!
voice class server-group 20
 ipv4 10.1.100.1 preference 1
 ipv4 10.1.101.1 preference 2 
 description to CUCM

dial-peer voice 10
 description OUTBOUND_PSTN_CALLS
 destination e164-pattern-map 10
 translate-called PSTN_FORMAT
 session protocol sipv2
 dtmf-relay rtp-nte
 session server-group 10

dial-peer voice 11
 description INBOUND_FROM_PSTN
 incoming called e164-pattern-map 20
 session protocol sipv2
 dtmf-relay rtp-nte
 session server-group 10
 dial-peer voice 20

dial-peer voice 20
 description TOWARDS_CUCM
 destination e164-pattern-map 20
 session protocol sipv2
 dtmf-relay rtp-nte
 session server-group 20

dial-peer voice 11
 description INBOUND_FROM_CUCM
 incoming called e164-pattern-map 10
 session protocol sipv2
 dtmf-relay rtp-nte
 session server-group 10
 dial-peer voice 20

voice translation-rule 10
 rule 1 /^911$/ /911/
 rule 2 /^9/ /+/
 
voice translation-profile PSTN_FORMAT
 translate called 10  

I have used a translation-profile to convert the dialed-numbers to +E164 numbers (except for 911 calls). This config is not required - it depends what format the PSTN is expecting the call. I have assumed that this telco here is expecing +E164 numbering format except for 911 calls.

​By the way, under the e164-pattern-map command, other than actual e164 numbers (like in example above), url could be used. which can point towards a file on the flash or ftp somewhere which can have the numbers.