ISDN Connectivity on HDX Units and Cisco NT BRI (2921 Gateway)

[Anonymous]

Hi,

We're in the middle of doing a telephony migration and having a few problems getting our HDX units to work with the BRI Channels.  We know our current config works (on Meridian Option 11 / CS1000) and we've had Cisco check over our BRI configuration but we seem to not be able to get any Layer 1 connectivity.

From what we understand the line should only come up when a call is initiated.  When running a trace on the 2921 we see the line come up and go down straight away when a call is initiated from the HDX units.  We've tried 3 HDX units (7000s and 8000) 3 different 2921 gateways all with different modules and still can't get any connectivity.

Our current BRI settings on the HDX that work on the Meridian are -

Numbering PLan - Unknown

ISDN Voice Algorithm - aLaw (we're in the UK)

ISDN Switch Proto - Standard ETSI

Line 1/2/3 with area code and directory no.

Software Version - Release - 3.0.0.1-14006

Anyone any ideas on this?

Cheers,

Peter

[Anonymous]

Ok, since you are able to get into the ISDN column on the HDX system means that your hdx system is detecting your BRI module correctly.

So, It might be a configuration issue, The first suggestion I tell people is to make sure they have all the correct informtion from the telco.

What are the light showing on the back of your ISDN module when you connect your BRI lines to it? Properly configured lines should show 2 solid green and amber lights, if not, there is a configuration issue.

[Anonymous]

Without changing any info (numbers codec etc) the HDX works on the Nortel.  Move the lines (exact same cables) to the Cisco 2921 and we dont get anything.  I've had 3 different CCIE Voice engineers confirm its configured correctly.

On the BRI module there is a solid green and amber light.  On the 2921 it Activates the link when a call is made but then drops it straight away.

Someone is now saying the Cisco 2921 isnt supported with HDX units? Surely this isnt true???

[Anonymous]

Pete,  the fact that the HDX works on the Nortel and not the Cisco obviously points to the Cisco.  I did some very basic quick research on the Cisco and did see that the data sheet mentions ISDN. 

Does it allow for ISDN circuit switched voice and data or only voice?  The Data is key.

What interface does the Cisco output?  'ST' or 'U'.  If it is 'U' then an NT1 device is required between the switch and the HDX ISDN module. 'ST' can plug in directly from switch to HDX.

Of course, as you know, the config must match between the HDX and switch. Which includes the switch protocol, dialing numbers and SPID's (if used).  

Ken...

[Anonymous]

Hi,

I believe the card is for Data (NT/TE) Also we also have just received a new unit that had some documentation on BRI module saying to be on a later HDX version than 2.0.0J is this different from the HDX 8000 version?  Currently we're on 3.0.0.1-14006

Many Thanks,

Pete

[Anonymous · Accepted solution]

It turns out it was ISDN adapters we were using (RS Electronics), the pinout was correct (below) however there were resistors inline that we assume were dropping the line voltage and not allowing layer 1 to come up.

Polycom BRI to Cisco 2921 or 2811 NT/TE requires the following cable -

ISDN Cross Pinout

1 - 1

2 - 2

3 - 5

4 - 6

5 - 3

6 - 4

7 - 7

8 - 8

Pins 1/2/7/8 arent required but I connected them to give strength to the RJ45 connector.