T1 PRI - power outage - inbound vs. outbound calling

[rcoote5902_2]

I have a site with a full T1 PRI for voice using mgcp, CUCM 7, 2 subscribers (one is at this location), 1 publisher.  There is no pots connectivity/redundancy at all at this site.  Today we had a power issue caused by a problem with a transformer on a pole outside the building.  Power was out for a couple of hours, however all of my gear stayed online via UPS, including phones on PoE switches.

In short all LAN/WAN connectivity, and phones stayed up throughout the outage.  Calls out worked fine, however calls in would not go through.

Relevant config from the gateway:

controller T1 2/0
framing esf
linecode b8zs
pri-group timeslots 1-24 service mgcp

!
interface Serial2/0:23
no ip address
encapsulation hdlc
isdn switch-type primary-ni
isdn incoming-voice voice
isdn bind-l3 ccm-manager
no cdp enable

!

voice-port 2/0:23
echo-cancel coverage 32
!
ccm-manager redundant-host 10.16.128.11 10.16.128.5
ccm-manager mgcp
no ccm-manager fax protocol cisco
ccm-manager music-on-hold
ccm-manager config server 10.16.128.5
ccm-manager config
!
mgcp
mgcp call-agent 10.16.32.7 2427 service-type mgcp version 0.1
mgcp dtmf-relay voip codec all mode out-of-band
mgcp rtp unreachable timeout 1000 action notify
mgcp modem passthrough voip mode nse
mgcp package-capability rtp-package
mgcp package-capability sst-package
mgcp package-capability pre-package
no mgcp package-capability res-package
no mgcp package-capability fxr-package
no mgcp timer receive-rtcp
mgcp sdp simple
mgcp fax t38 inhibit
mgcp rtp payload-type g726r16 static
mgcp behavior g729-variants static-pt
!
mgcp profile default

I'm stumped as to why outbound calls were successful (on-net and off-net) yet calls to DID's assigned to this PRI would not ring through. (Number unavailable announcement).

Obviously if we have UPS providing phone service in event of a power outage I'd like calls to still be able to come into the site. :/

Any thoughts would be appreciated.

Thanks,

Rob

[Brandon Svec]

Hi, one (the only?) logical explanation for this is that your PRI was, in fact, down durung the power outage even though the rest of your equipment was up. Did you happen to check this during that period?

Outbound calls must have worked because you have a secondary route to send calls out another way.  This might be via FXO or via IP and out another office's PSTN.

You might want to talk to your service provider about what happens to inbound calls when your T1 is down.  Typically, you can pay a small monthly fee to have them redirected somewhere.  A common scenario is to redirect to a hunt group of FXO lines particularly for this purpose.  Keep in mind though that *all* calls to the T1 would overflow, so even individual DID numbers would end up going to one number in case of an outage so you would point these FXO lines to an auto attendant or operator to handle.

Brandon

[rcoote5902_2]

That is what has me confused.  There is no secondary route for calls, it is solely through that PRI.  I have in the past set up temporary re-routing of calls through another site's FXO groups in emergencies, but verified that there is nothing like this configured at this site.

I'm still scratching my head, and unfortunately have no way to try and reproduce the event...short of tripping some breakers at the site, and that would significantly shorten my career.

[Brandon Svec]

Well, now two of us are scratching are heads about this

I guess for your own satisfaction (and perhaps your boss's) you should schedule a maintenance time to test this and if you see the same symptoms you can run some debugs and discover what is going on.  If what you say is accurate outbound calls must be routing somewhere.

I guess another slight possibility is that there was some coincidental or related telco outage along with the power outage where you service provider was actually having the trouble you described of not allowing inbound.  This seems pretty unlikely though.

OK, one last possiblity is that since you weren't on site I assume you are relying on reports from the end user.  You probably know where I am going with this one..  Maybe the T1 was bouncing up and down so when you tested inbound it failed, but when a user called out it happened to be back up and worked.

In any case it would seem to be in your best interest to test it when you can and make sure you have a back up plan in case it happens again.  It is a bit of an incomplete backup plan to have all the equipment remain up, but no alternate routing in case of simple PRI failure.

Brandon

[rcoote5902_2]

I have to go with the coincidental theory at this point.  Since it was a telco message I'm going to go with that.  It's the only sane explanation.

I was actually on site and testing the calling myself.