[cisco-voip] Modem PassThrough

Mon Jan 14 11:26:16 EST 2008

Show controller e1, any clock slips anywhere ? Any noisy lines?

Ask teleco to check their ends and run tests.

From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Ramiz Sardar
Sent: Monday, January 14, 2008 11:20 AM
To: cisco-voip
Subject: Re: [cisco-voip] Modem PassThrough

Thanks for reply. Alaw is used for E1 so this shouldn't be an issue.
Anyone else have idea, please help me.............

Waiting....
Best Regards

On Jan 14, 2008 8:58 PM, Scott Voll < svoll.voip at gmail.com> wrote:

only thing I can think is *maybe* there's a difference between Alaw and
Ulaw.  other then that..... I don't know. 

Scott

On Jan 14, 2008 12:41 AM, Ramiz Sardar <ramizchaudhary at gmail.com> wrote:

Friends,

I configured routers with for modem passthrough. When my modem dial RAS
number, It starts negotiation with RAS but keep negotiate and not
connected. Means repeat negotiation again and again till timeout. Once
it surprisingly connected but within 30 sec it disconnected. Network
Topology below: 

RAS--------PBX-----Rt-A--------------------Rt-B----PBX-----------DialupU
ser  

And Configuration below:   

hostname Rt-B

isdn switch-type primary-qsig 

voice service voip 
 modem passthrough nse codec g711alaw

controller E1 0/0/0
 channel-group 0 timeslots 1-31 

controller E1 0/1/0
 pri-group timeslots 1-31

interface Serial0/0/0:0 
 ip address 10.0.0.2 <http://10.0.0.2/>  255.255.255.252
<http://255.255.255.252/> 

interface Serial0/1/0:15
 no ip address
 encapsulation hdlc
 isdn switch-type primary-qsig 
 isdn overlap-receiving
 isdn incoming-voice voice
 isdn bchan-number-order ascending 
 no cdp enable

router ospf 100
network 0.0.0.0 <http://0.0.0.0/>  255.255.255.255
<http://255.255.255.255/>  area 0

dial-peer voice 786 voip
  destination-pattern 786$
  modem passthrough nse codec g711alaw 
 session target ipv4:10.0.0.1 <http://10.0.0.1/> 
 no vad
!
dial-peer voice 785 pots
 incoming called-number 786$
 direct-inward-dial 
 port 0/1/0:15

-------- Router A --------- 

 hostname Rt-A
isdn switch-type primary-qsig 
!

voice service voip 
 modem passthrough nse codec g711alaw
!
controller E1 0/0/0
 channel-group 0 timeslots 1-31 

controller E1 0/1/0
 pri-group timeslots 1-31

interface Serial0/0/0:0
 ip address 10.0.0.1 <http://10.0.0.1/>  255.255.255.252
<http://255.255.255.252/> 

router ospf 100
 network 0.0.0.0 <http://0.0.0.0/>  255.255.255.255
<http://255.255.255.255/>  area 0

dial-peer voice 786 pots
 destination-pattern 786$
 direct-inward-dial
 port 0/1/0:15 
 forward-digits 3
!
dial-peer voice 785 voip
 modem passthrough nse codec g711alaw 
 incoming called-number 786$
 no vad    

Waiting for your immediate response....... 

Best Regards 

On Jan 9, 2008 9:42 PM, Scott Voll <svoll.voip at gmail.com> wrote:

Modem pass through is just like Fax passthrough.  both need to run over
a G711 codec.

config is pretty simple.  just add the following commands:

H323 looks like this:

 voice service voip
 h323
 modem passthrough nse codec g711ulaw

Also make sure you have VAD turned off on the dial peer(s)

MGCP looks like this:

mgcp modem passthrough voip mode nse

Scott

On Jan 9, 2008 7:15 AM, Ramiz Sardar <ramizchaudhary at gmail.com> wrote:

	Friends,

	I am currently working on voip setup. With the existing tdm
network, dialup users from different sites dial Remote Access Server in
central site. When i will put routers into that network, can users be
able to connect again via voip setup. Topology includes cisco 3800
routers that connect with Ericson MD110 pbx through E1 (Pri Qsig).
Routers are connected point to point through E1. RAS is non-cisco. 

	Existing Topology:

	IP Network
---------RAS------------PBX--------------------------------------------P
BX--------------Dialup User (Modem)

	Topology after voip setup:

	IP Network
---------RAS------------PBX---------Router-----------------------------R
outer--------PBX--------------Dialup User (Modem) 

	With some study i come to know that there is concept of modem
passthrough that can be used but someone please explain it briefly. And
if someone currently using it, please write down a sample configuration
according to my voip topology. 

	Best Regards

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