Solved: Re: SRST inter-site calling

KhanalZ · ‎06-28-2024

I have main site with CUCM cluster and its own voice gateway (PRIs). There is a small remote site with the voice gateway with a single PRI (for outbound calls only). Sites are connected with WAN link. Inbound calls for remote site comes to the main site gateway. Remote and main site uses the numbers from the same DID range which means remote site does not have its own separate DID range.

When there is a wan failure between the main and remote site, remote site phones go to SRST mode as expected and they can make outbound calls without issues. However, they cannot call the main site using the 4 digit because there is no dialplan for 4 digit dialing in that gateway. I am wondering how I can accomplish this with minimal effort. Is it just a matter of translating 4 digits to 10 digits (or e164 format in our case) or there is more to it? Again, since both sites use the numbers from the same DID pool, we may not be able to use the wildcards if we need to use translation profiles. My requirement is just to allow people from remote site to be able to call main site using 4 digit extensions while in srst mode.

Thanks

KhanalZ

Roger Kallberg · ‎07-27-2024

Change rule 2 to translate to +E.164 format by this.

voice translation-rule 50
rule 1 /9$[2-9]..[2-9]......$$/ /91\1/
rule 2 /^$11..$$/ /+1202555\1/

Then create a new dial peer that matches +1202555T and also create a new translation rule and profile that translates from +E.164 format to the format required by your service provider to route the call on PSTN, then set that translation profile on the new dial peer as an outbound translation.

With this your router will when the phones are in SRST state see the dynamically created dial peers first and keep the call locally and if the +E.164 number isn’t available locally on the router it will use the new dial peer and send the call via PSTN to your other site.

Likely the translation rule and profile should be like this.
voice translation-rule 51
rule 1 /^\+$.*$/ /\1/
!
voice translation-profile E164-OUT
translate called 51

The key to this is that the outbound translation is done after the dial peers is matched and that the dynamic dial peers will have a more specific match than the new dial peer as they have the complete directory number, making them a better match than the new dial peer.

None of this will make any difference to your normal dial strings to PSTN. It will just create the possibility to route calls to your other site in +E.164 format and use the call routing logic in IOS to keep the call locally when there is a directory number registered on the router.

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