fractional T1 routing to Fax server

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Dec 15th, 2008
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We migrated a fax server that needed 8 ports (fractional T1) and we have it live running through our old PBX (in one T1 card and out another). We received a Cisco 2600 that has 2 T1 cards in it that seems it should be able to be programmed for the same function. Is this possible and if so are there any config examples?

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Richard Burts Mon, 12/15/2008 - 14:10
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Troy


The ability to take a T1 incoming and process a group of channels so that they are output on channels of an outgoing T1 is generally referred to as Drop and Insert. Whether your 2600 can do this or not is mostly dependent on the type of T1 card that is installed on the router. Some T1 cards are capable of drop and insert and some are not.


This link provides some information and configuration example for configuring drop and insert:

http://www.cisco.com/en/US/docs/routers/access/1700/1721/software/feature/guide/t1e11721.html#wp148178


HTH


Rick

tweller Tue, 12/16/2008 - 08:59
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The fax server is using a brooktrout fax board. I don't believe it needs an IP assigned. Would the router have the T1 traffic in the WIC and oit the ehternet interface to the fax server? Or would I need two T1Wic's in the Router?


Richard Burts Tue, 12/16/2008 - 10:53
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Troy


Fax servers are not a strong point in my experience, but I also believe that it does not need an IP address. I do not believe that the existing situation has the PBX routing IP to the fax server, and I do not believe that the new situation would want the router routing IP to the fax server.


I am not clear about some aspects of your current situation. In particular it is not clear to me whether the fax server is connected to the PBX and the PBX serves as the gateway to the PSTN for fax, or whether the PBX is just transfering 8 channels from a T1 connecting to the fax server to 8 channels on another T1 which goes to the gateway to the PSTN for the fax server (which is what I think your description sounds like). In the first case I believe that you need the PBX and the router can not substitute for it. In the second case it is the capability that I described as drop and insert. It does use 2 T1 cards and does not use the Ethernet interface.


HTH


Rick

tweller Tue, 12/16/2008 - 10:59
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ok it is currently setup as the second scenario you outlined above. So in the config example I would use the 1700 part of the example:


card type t1

controller T1 0

framing esf

linecode b8zs

tdm-group 2 timeslots 13-24

!

controller T1 1

framing esf

clock source internal

linecode b8zs

tdm-group 3 timeslots 1-12

!

connect dfw1 T1 0 2 T1 1 3



Instead of 12 I would use 8 timeslots but why does it use different timeslots for each tdm-group?

Richard Burts Tue, 12/16/2008 - 11:23
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Troy


Yes if it is set up as the second scenario then this is the type of config that you would use (assuming that your T1 cards support the ability to do drop and insert).


Yes you would use 8 timeslots rather than 12. The example uses different timeslots for each tdm-group just to demonstrate that you can map to different time slots (they are not required to be identical on each T1). Fundamentally you need to configure the router to match what the existing configuration does. If they use the same time slots on each T1 then you use the same time slots on each T1. The fax server and its PSTN gateway need to continue to see the channels that they are expecting to see.


HTH


Rick

tweller Tue, 12/16/2008 - 11:39
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Ok Rick, thanks for the insight. This project will probably be bumped to Jan. so I won't know until then if it is sucessfull but I will try it and let you know.





Richard Burts Tue, 12/16/2008 - 11:51
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Troy


If there is likely to be some delay in the project, I would suggest that you might want to go ahead and figure out whether the T1 cards in your router do support drop and insert. The easy way would be to go into config mode and see if the tdm-group and the connect commands show up in the right mode. Or you could tell us what kind of card the T1 card is (the output of show diag would be helpful for that).


HTH


Rick

Nicholas Matthews Mon, 12/15/2008 - 19:52
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If this is a T1 PRI connection to the fax server it is very much possible.


pri-group 1 timeslots 1-8,23


That would be the approximate 8 B-channel partial PRI you could be looking for.


You'll want to be aware that partial PRIs aren't supported via MGCP on CCM (if this is applicable)


If this is an IP fax server you can disregard, as that configuration would be different.



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