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New Member

Unity 4.0 failover and PBXlink

Help! When using a PBXlink unit to connect to a Nortel PBX when there is also a failover Unity server involved, which is the correct design:

(1) Two sets of PBXlink boxes, each connecting individually to the two Unity servers. This approach is indicated in the Unity Nortel configuration doc on CCO as correct.

(2) One set of PBXlink boxes, connecting to both Unity servers via some sort of SMDI splitter. I've seen this design put forward but have never seen one actually implemented myself.

Also, in terms of an SMDI splitter, if available what part number is this? Is this the UNITY-FOVR-ANSPLT part?

Cisco Employee

Re: Unity 4.0 failover and PBXlink

Both designs should work fine however the first one recieved the most emphasis in testing at Cisco. The SMDI splitter was primarily intended for environments where it is not otherwise possible to configure a second serial link.

Details on the splitter are available from B&B Electronics,

The Cisco part number you gave looks more like it might be refering to the analog phone line splitter. Someone else will have to confirm that for you.


New Member

Re: Unity 4.0 failover and PBXlink

Hi, I have a question on PBXlink failover setting with Nortel PBX.

1) FOr my UM system with Nortel M1, there will be 36 ports involved. So I have to set up 2 PBXLinks on each Unity server. In this case, I will use Port A and B on PBXLink #1 and Port A Only on PBXLink #2. For PBXLink #1, do I need to use 1 digital line or 2 digital lines?

2) As far as I know, those analog lines connecting with Active Unity server has to be connected with Standby Unity server as well. However, for those digital lines, if I have 3 digital lines connecting with PBXlinks on active and another 3 digital lines on standby server, does the primary numbers on those 3 digital lines on Active side be the same to different from the primary numbers on those 3 digital lines on Standby side?



Raymond CB Lai

Cisco Employee

Re: Unity 4.0 failover and PBXlink

Hi Raymond,

Hopefully this answers your questions...

1) Each digital port that you use on the PBXLink will need a digital line from the PBX. I recommend that you configure Port A on PBXLink 1 to handle MWI only. Then use Port B on PBXLink 1 to monitor the odd numbered analog lines to Unity and use Port A on PBXLink 2 to monitor the even lines.

2) The primary numbers on the PBXLinks isn't terribly important. In fact, you should try to choose numbers that folks won't be accidentally dialing. Nobody should be calling them directly. You'll have a single group of 36 analog lines that split off to both Unity servers. Each pair of PBXLinks will be configured with bridged line appearances to monitor this group of 36 analog lines.



New Member

Re: Unity 4.0 failover and PBXlink

Hi Eric,

Really thanks for your reply and your answers are very helpful to my design and deployment. However, may I ask you two more question on the Unity failover with PBXlink?

1) Once I went through the configuration of PBXlink, it mentioned that each analog line must only be associated with 1 digital line only. So in my failover case, as those analog lines would associate with those digital lines on PBXlinks on Active Unity, would the digital lines on those "failover" PBXlinks on the standby Unity associate with those analog lines as well? How will the Nortel PBX know whether it will use the digital line on the Active Unity side or Standby Unity side as both digital lines associate with the same analog lines.

For the reference document, please refer to

2) When I went through the same document, it told me that if the number of message port is less than 30, I should use the hunt group, otherwise, I should use the ACD hunt group instead. Well, in my case, I believe that I need to deploy the model with ACD hunt group as I have 36 analog ports involved. My question is: If I use the ACD group, do I still need to configure all analog ports such that if this analog port is busy or available, it will forward the call to the next analog port? Isn't it the same as the ordinary HUNT group and we are deploying both HUNT group and ACD HUNT group at the same time?

Really thanks for your help.


Raymond CB Lai

Cisco Employee

Re: Unity 4.0 failover and PBXlink

I don’t recall the integration guide containing any mention “that each analog line must only be associated with one digital line”. On the contrary, if you have two sets of PBXLink boxes, one for each Unity server, then both sets of PBXLinks should simultaneously monitor inbound call activity for each of your voicemail analog lines. Neither the Nortel nor the PBXLink devices will have any knowledge about which Unity server is active and which is inactive. The inactive server will simply ignore incoming call rings and SMDI data. Perhaps there is an error or misleading comment in the integration guide?

For the ACD question you might be better off consulting your Nortel tech. My understanding is that in both cases the actual “hunting” is simply a station forwarding chain. The catch is that the Nortel will limit the number of forwarding hops such that a simple chain can not be longer than 30 vm ports. Thus when more than 30 ports are needed we break the chain up into small sections and lead each off with an empty ACD group. Again, your Nortel tech should be able to better explain how/why the Nortel works this way. Ideally, hunting should be done in a distributive fashion (e.g. circular hunting or even longest-idle is much preferred over always banging on port 1 with linear hunting). However, I do not believe this is possible on the Nortel PBX.

Hope this helps.

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