Question on VG224 and gateway for CUCM Subscriber

[news2010a]

Imagine I have future site to design with 2,000 Cisco IP Phones 7962G . There are 200 analog phone lines that need to be maintained as analog phone lines.

I will install 1 CUCM subscriber and publisher and subscriber will be housed in a collo facility (latency requirements, bandwidth for ICCS OK).

Requirement is that even the WAN MPLS circuit between this large remote site and collo provider fails, users should have intra building dial-tone and be able to call 911 and call offnet to other locations. For that reason, In addition to the CUCM 8.6 (or 9.0) subscriber onsite, I will also install a 3945E connected to POTS lines to allow the 911 and offnet capability.

Question:

In order to let the 200 analog phones work, do I have to buy a dedicated VG224 gatway and bring dedicated POTS line for those?
Or somehow I could use the 3945E with FXS ports to allow such 200 analo phones to work?

I believe it is the former, but I just wanted to make sure.

[Chris Deren]

I think you may be confusing POTS lines with analog device ports.  If you need 200 analog devices such as faxes, modems, analog phones connected to your Cisco IPT system you will need analog GWs, your cheapest solution currently available will be VG224s. Each VG224 provides 24 analog connections. There are some FXS bundles for VGs but they are nightmare to manage from cabling point of view and configuration.

HTH,

Chris

[news2010a]

1) Sorry for my ignorance, but do you connect all those VG224s gateways to accomodate 200 analog phones to the PSTN?
Or is the VG224 boxes connected to the IP swich then reach the IP PBX (CUCM)?

2) Now imagine in case the WAN dies between my remote site (with 1 CUCM subscriber) and CUCM pub+sub is in the collocation facility. My goal is to let BOTH ip phone users and analog phone users make/receive inbound and offnet calls and call 911.

Then I would get a 3945E with FXO ports connected to POTS line correct to let CUCM users call offnet? I mean the 3945E connected to FXO to let CUCM and IP phone make calls to 911 and offnet has nothing to do with VG224s, right?

[Chris Deren]

VG224s do not connect to PSTN, VG224 is for your analog devices such as faxes, so that you can put the faxes on your Cisco infrastructure.  Again, you need to differentiate PSTN POTS lines from internal analog devices.

I don't see a compelling reason why one would need 200 POTS lines to PSTN as the cost would be huge anywhere in the world and you are much better of with either PRIs or SIP trunks.

VG224 has RJ21 connection for patch panel/block and RJ45 network connection to plug it to the network switch.

2. Sure, either have local CUCM at this site, or configure the voice gateway (i.e. ISR2 router providing PSTN connection) with survivability (SRST), you need to ensure you have local PSTN trunks, but with this many users you should have local GW anyone.

Again, not sure what you are looking at FXO lines rather than PRI for this many users, either way yes FXO can connect to PSTN and provide outbound dialing, yes nothing to do with VG224:

analog device ---physical connection--- VG224 --ip--- CUCM --ip--  VGW(3945) ----pstn

HTH, please rate all useful posts!

Chris

[Rob Huffman]

Hey Chris,

Great answer here buddy! +5

Just curious if you've had any oppotunity to use the Cisco 112-FXS (is that your earlier

"nightmare" reference) ??

We need to replace our VG248's at some point and thought about going this route

Cheers!

Rob

"Show a little faith, there's magic in the night" - Springsteen

[Chris Deren]

Thanks Rob.

I personally have not used it, but some of my colleagues have and did not like it.

I do miss VG248, but I hear "rumors" that other higher capacity replacement is coming :-)

Chris

[Rob Huffman]

Hey Chris,

Thanks for this feedback my friend +5

Yeah, I still can't figure out why Cisco didn't stick with the VG248's

We have about 15 of them and I've always found them to be pretty great.

That's Cisco for you, always some curious thoughts going on over there

Cheers!

Rob

"Show a little faith, there's magic in the night" - Springsteen