Multiple ISDN Switch Types

[VAbr AVib]

How to configure multiple switch types on a Cisco Voice Router ? Attaching the diagram for reference.

I need to connect one PRI card to the PBX and the other card to the PSTN PRI.

I am having Cisco 2951 series router? Does this router support multiple PRI Connectivity ?

[Harmit Singh]

Hi Vibi,

Yes, it does. The thing to watch out for is clocking. If the router is receiving the clock from both PBX and PSTN provider, then you need to make sure both PRIs terminate in seperate clocking domains to avoid slips. In other words, your motherboard would be one clocking domain while you could go with an NM-HDV2 module which would serve as the second clocking domain. As for the switch-types, you can specify each switch-type under the Serial Interface of each PRI. This config takes precedence over the global switch-type configuration.

HTH.

Regards,

Harmit.

[VAbr AVib]

Thanks a lot Harmit.

In that case how do i mention the switch type? I should anyway mention the switch type globally and then at the interface level.

Also just found this link where they say, multiple ISDN switch type is supported for the mentioned platforms only.

http://www.cisco.com/en/US/docs/ios/11_3/feature/guide/multisdn.html#wp7721

Platforms:

This feature is supported on these platforms:

•Cisco 3600 series

•Cisco 4000 series

•Cisco 5200

•Cisco 5300

•Cisco 7200 series

•Cisco 7500 series

[Harmit Singh]

Hi Vibi,

That document is very old and refers to IOS version 11.x :-)

However, the logic it mentions is still the same. The command is "isdn switch-type " where type is whatever switch-type you need to configure. Apply this under the serial interface once the PRIs are configured.

HTH.

Regards,

Harmit.

[VAbr AVib]

As you told let me check the clocking settings, also i should go for NM-HDV2 module right.......

Thanks a lot.....

[Harmit Singh]

Yes, look for "Analog and Digital Voice/Fax" in the following doc:

http://www.cisco.com/en/US/products/ps10536/products_relevant_interfaces_and_modules.html#voicemod

Regards,

Harmit.

[acampbell · Accepted solution]

Vibi,

I think this may help you.

In this config we have 7 PRIs
6 are for PSTN and 1 for QSIG.

We are taking the clock from the PSTN and
if they all fail we use the clock from the
PBX QSIG

.

We are also emulating the network end for the QSIG PBX link.

!
network-clock-participate wic 0
network-clock-participate wic 1
network-clock-participate wic 2
network-clock-participate wic 3
network-clock-select 1 E1 0/0/0
network-clock-select 2 E1 0/0/1
network-clock-select 3 E1 0/1/0
network-clock-select 4 E1 0/1/1
network-clock-select 5 E1 0/2/0
network-clock-select 6 E1 0/2/1
network-clock-select 7 E1 0/3/0
!
isdn switch-type primary-net5
!
!
!
interface Serial0/0/0:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/0/1:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/1/0:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/1/1:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/2/0:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/2/1:15
desc *** TO PSTN ***
isdn switch-type primary-net5
isdn overlap-receiving T302 2000
isdn incoming-voice voice
no cdp enable
!
interface Serial0/3/0:15
desc *** TO PBX QSIG ***
isdn switch-type primary-qsig
isdn timer T310 120000
isdn overlap-receiving T302 2000
isdn protocol-emulate network
isdn incoming-voice voice
no cdp enable
!

Regards,
Alex.
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[VAbr AVib]

Thanks a lot Alex for your detailed note. Could you please verify the dial peer in this case ?

I am planning to have the below dial peers for PBX extensions and PSTN calling:

dial-peer voice 15 pots

  destination-pattern 3...     'PBX Extensions 3XXX

  incoming called-number .T

  port 0/0/0:15              ' Connected to PBX

  forward-digits all

dial-peer voice 16 pots

  destination-pattern 3...   

  incoming called-number .T

  port 0/0/1:15         ' Connected to PBX

  forward-digits all

dial-peer voice 17 pots

  destination-pattern 86.T        ' PSTN Access Code '86'

  incoming called-number .T

  direct-inward-dial

  port 0/1/0:15           ' Connected to PSTN

dial-peer voice 18 pots

  destination-pattern 86.T     

  incoming called-number .T

  direct-inward-dial

  port 0/1/1:15          ' Connected to PSTN

[acampbell]

Vibi,

Primarily your dial peers are good.

May be you need to consider how you want the outgoing
calls to flow.

You can set a preference in each dial peer.

Lets say you want the outgoings calls to always use the
1st PRI and use the 2nd choice if all channels are busy.

!
!
dial-peer voice 15 pots
destination-pattern 3...     'PBX Extensions 3XXX
incoming called-number .T
port 0/0/0:15              ' Connected to PBX
forward-digits all
pref 1
!
!
dial-peer voice 16 pots
destination-pattern 3...   
incoming called-number .T
port 0/0/1:15         ' Connected to PBX
forward-digits all
pref 2
!
!
dial-peer voice 17 pots
destination-pattern 86.T        ' PSTN Access Code '86'
incoming called-number .T
direct-inward-dial
port 0/1/0:15           ' Connected to PSTN
pref 1
!
!
dial-peer voice 18 pots
destination-pattern 86.T     
incoming called-number .T
direct-inward-dial
port 0/1/1:15          ' Connected to PSTN
pref 2

Regards,
Alex.
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[VAbr AVib]

Alex, Thanks a lot for your valuable comments.

Looking at the DSP requirements since more resouces might be required when we have both PSTN and PBX terminating on the same router. I have two DSP (PVDM3-32,PVDM3-64) and the maximum channel usage currently is around 20 CH during peak hours. Do I need to add more DSP's ?

[acampbell]

Vibi,

If you want to run all 4 PRIs with full 30 channel capacity you will

need to add or change your DSP set up.

As a minimum you need to upgrade the PVDM3-32 to a PVDM3-64

Please remember that this will leave you with no additionalo DSP resources to provide

IOS trancoding,conferencing or MTP.

If you can afford (money) then replace the PVDM3-32 with a PVDM3-128.

Hope this helps

Regards,
Alex.
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[VAbr AVib]

We will not have much load on the router except for the timeslots and transcoding.

The Router model 2951 has 3 DSP slots, I think it is better we add another chip of PVDM3-64 (Total=> 32+64+64). So if am not buying any more DSP's then I think I have to reduce the timelots for PBX PRI ports ?

CUCM Software  MTP and Conference Bridge is used and following is the IOS transcoder details.

dspfarm profile 2 transcode

codec g711ulaw

codec g711alaw

codec g729ar8

codec g729abr8

codec g729r8

codec g729br8

codec g722-64

maximum sessions 10

associate application SCCP

Alex, Your thoughts !!!!

[acampbell]

Vibi,

I have just ran your dsp commitments through the dsp calculator

http://www.cisco.com/web/applicat/dsprecal/dsp_calc.html

To run full 120 channels over the 4 E1 PRIs and 10 session Transcoder you will need

PVDM3-192

You will need to cut down the channels,

looks like you would need to reduce to 106 channels & 10 sess transcode

Try the calculator yourself

Regards,
Alex.
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[VAbr AVib]

Thanks a lot Alex.

As you told i will work on the channel requirements, i will monitor the channel usage trend and finalize the max number of channels required for both PBX and PRI ports. So based on that can decide what sort of DSP change is required. As you suggested, if i plan for 60 PSTN channels and 46 PBX channels we still need another PVDM3-64 right? And since i am adding PSTN to the new PRI card, do you think we need to add more transcoding sessions or 10 is sufficent ?

I also noticed that there is one error message when i run "sh voice dsp group all" stating "4 DSP resource allocation failure", i need find out the cause for that as well.

Do you have any idea why there is a DSP failure when the number of channels used are below 10 ?

[acampbell]

Vibi,

You could be hitting a BUG

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCsx67255

The follwing IOS versions are affected

15.0(1r)  

15.0(1r)M1  

15.0(1r)M2  

15.0(1r)M3  

15.0(1r)M4  

15.0(1r)M5  

15.0(1r)M6  

15.0(1r)M7  

15.0(1r)M8  

15.0(1r)M9  

15.0(1r)M10  

15.0(1r)M11  

15.0(1r)M12  

15.0(1r)M13  

15.0(1r)M14  

15.0(1r)M15  

15.1(2r)T  

15.1(2r)T1  

15.1(2r)T2  

15.1(2r)T3  

Regards,
Alex.
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