SRST Hairpin to PSTN

[William Bell]

I have searched through the forum and I have seen various threads on this topic but none that fit my particular scenario/question.  I have an ISR voice gateway at a remote site (IOS 12.4(24)T2) that is configured to be an SRST router for phones at the remote site.  This voice gateway is also configured to run H.323 (i.e. no MGCP).

When in SRST mode, I want calls to a specific DID to be hairpinned back out to the PSTN to a different called party number.  If the gateway was running MGCP with fallback to H.323, then this would be simple.  The method for a MGCP approach is to have a pots dial-peer with an inbound translation profile that would redirect to the PSTN, like so:

voice translation-rule 10

rule 1 /2025551000/ /914105559999/

!

voice translation-profile redirecttopstn

translate called 10

!

dial-peer voice 100 pots

description inbound dial-peer

incoming called-number 202555....

...snip...

translation-profile incoming redirecttopstn

...snip...

!

dial-peer voice 200 pots

description a normal LD dialpeer

destination-pattern 91[2-9]..[2-9]......

...snip...

!

Now, the problem when the gateway is running H.323 is that I don't need to do the redirection because the WAN is healthy, and I can just route the call to my CUCM cluster using the voip dial-peer.  However, if I were to put in the translation-profile approach as shown above, all calls to the target DID would redirect whether the WAN is healthy or not.

So, I need something that would only be inserted in the call path when SRST is engaged.  Any thoughts?

Regards,

Bill

Now

[James Hawkins]

Just seen that this is a thread resurrected from 2010 - leaving my answer as it may be useful to someone.

Hi Bill,

I used Embedded Event Manager to solve a similar call routing issue with SRST.

EEM was configured to track the availability of CUCM servers via ICMP pings. If the pings were lost then EEM shut down certain dial peers and enabled others. When the servers became available EEM reversed the changes.

Sample config below:

!

track 1 ip sla 10 reachability

!

track 2 ip sla 20 reachability

!

track 3 list boolean or

object 1

object 2

!

!

ip sla 10

icmp-echo 172.27.240.129 source-interface Loopback0

frequency 5

ip sla schedule 10 life forever start-time now

ip sla 20

icmp-echo 172.27.240.193 source-interface Loopback0

frequency 5

ip sla schedule 20 life forever start-time now

!

event manager applet cucm_servers_unreachable

event track 3 state down

action 1.0 syslog msg "Ping has failed. CUCM servers unreachable"

action 2.0 cli command "enable"

action 2.1 cli command "conf t"

action 2.2 cli command "dial-peer voice 10 pots"

action 2.3 cli command "shutdown"

action 2.4 cli command "dial-peer voice 11 pots"

action 2.6 cli command "no shutdown"

action 2.7 cli command "dial-peer voice 100 pots"

action 2.8 cli command "shutdown"

action 2.9 cli command "dial-peer voice 101 pots"

action 3.0 cli command "shutdown"

action 3.1 cli command "dial-peer voice 200 pots"

action 3.2 cli command "no shutdown"

action 3.3 cli command "dial-peer voice 201 pots"

action 3.4 cli command "no shutdown"

action 4.0 syslog msg "SRST dial-peers activated"

event manager applet cucm_servers_reachable

event track 3 state up

action 1.0 syslog msg "Ping has succeeded. CUCM servers reachable"

action 2.0 cli command "enable"

action 2.1 cli command "conf t"

action 2.2 cli command "dial-peer voice 11 pots"

action 2.3 cli command "shutdown"

action 2.4 cli command "dial-peer voice 10 pots"

action 2.6 cli command "no shutdown"

action 2.7 cli command "dial-peer voice 100 pots"

action 2.8 cli command "no shutdown"

action 2.9 cli command "dial-peer voice 101 pots"

action 3.0 cli command "no shutdown"

action 3.1 cli command "dial-peer voice 200 pots"

action 3.2 cli command "shutdown"

action 3.3 cli command "dial-peer voice 201 pots"

action 3.4 cli command "shutdown"

action 4.0 syslog msg "SRST dial-peers deactivated"

!

I think this could be improved by tracking TCP connections to port 2000 on the CUCM servers.

I hope this is of interest.

Regards

James