Voice over IP Cisco - IAD 2420 - modem dial out issue

Author

IAD 2420 - modem dial out issue

John Kienzle

2005-11-29, 5:45 pm

Hello.

Our company uses analog lines for fax and modem dial out provided by an
IAD 2420 which is connected to a 3725 router handling our PRI T1 phone
trunks. Incoming and outgoing faxes work fine, the numbers associated to
the IAD all work ok - we can make and receive calls. The problem we are
experiencing is this - we have a couple workstations with modems that
call out to gas control meters in the field and retrieve data. There are
2 types of collection performed. One retrieves the current status and
another retrieves monthly historical data. The status data always
collects fine. The historical data, which is a larger amount of data,
does not collect. There is usually some kind of CRC error or character
timeout error reported by the software. We have verified it is not
related to the equipment in the field, as it works just fine over a
standard 1FB analog line. Just not through our IAD. Recently we migrated
from catalyst 2924 and 3524 switches to a 6509 running IOS. I have since
put the IAD back to the 2924 where it was originally connected. Our IP
Address network has also changed, but the collection has been working
fine after that migration.

One thing I have noticed is that the IAD appears to only run 10 meg
half-duplex from its Ethernet port. Thus, I have noticed collisions and
deferred packets on the E0 interface and the switchport, which I would
probably expect from half-duplex ethernet operation. I have tried
forcing full duplex on the IAD Ethernet port, but the switch still shows
it connected as half-duplex.

Does anyone have ideas on other areas I might look for answers related
to this issue? Could it be a Qwest (PRI provider) issue with our PRI? I
may open a TAC case, but thought I'd try this forum first.

Thanks.

John Kienzle
Western Gas Resources
Field Support Analyst

Fred Nielsen

2005-11-29, 8:45 pm

Are you saying that the modem application works okay when the IAD is
connecting to your stackables but not the 6500, or doesn't work in either
situation? Has it ever worked? For the below, I am assuming the behavior
is similar regardless of the data switch connectivity.

While the duplex issue is something to get worked out (have you tried
forcing both sides to full-duplex?) I am also curious about what type of
modems you are using (i.e. V.34) and what connection speeds you are
attempting. Generally you start to get into trouble at speeds above
14.4kbps, at least in my experience. I assume you are using the FXS ports
on the IAD to connect analog modems at the head end, and then traversing via
voip to the 3725 PRI. What sort of codec is configured in use between these
two endpoints? And finally, have you looked into configuration of "modem
passthrough" (not sure how well the IADs support this)?

_____

From: cisco-voip-bounces@puck.nether.net
[mailto:cisco-voip-bounces@puck.nether.net] On Behalf Of John Kienzle
Sent: Tuesday, November 29, 2005 9:36 AM
To: cisco-voip@puck.nether.net
Subject: [cisco-voip] IAD 2420 - modem dial out issue

Hello.

Our company uses analog lines for fax and modem dial out provided by an IAD
2420 which is connected to a 3725 router handling our PRI T1 phone trunks.
Incoming and outgoing faxes work fine, the numbers associated to the IAD all
work ok - we can make and receive calls. The problem we are experiencing is
this - we have a couple workstations with modems that call out to gas
control meters in the field and retrieve data. There are 2 types of
collection performed. One retrieves the current status and another retrieves
monthly historical data. The status data always collects fine. The
historical data, which is a larger amount of data, does not collect. There
is usually some kind of CRC error or character timeout error reported by the
software. We have verified it is not related to the equipment in the field,
as it works just fine over a standard 1FB analog line. Just not through our
IAD. Recently we migrated from catalyst 2924 and 3524 switches to a 6509
running IOS. I have since put the IAD back to the 2924 where it was
originally connected. Our IP Address network has also changed, but the
collection has been working fine after that migration.

One thing I have noticed is that the IAD appears to only run 10 meg
half-duplex from its Ethernet port. Thus, I have noticed collisions and
deferred packets on the E0 interface and the switchport, which I would
probably expect from half-duplex ethernet operation. I have tried forcing
full duplex on the IAD Ethernet port, but the switch still shows it
connected as half-duplex.

Does anyone have ideas on other areas I might look for answers related to
this issue? Could it be a Qwest (PRI provider) issue with our PRI? I may
open a TAC case, but thought I'd try this forum first.

Thanks.

John Kienzle
Western Gas Resources
Field Support Analyst