NM-1T3 E3 and PA-2T3 Compatibility

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Aug 4th, 2010
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We are in the process of connecting to France Telecom as our first mile provider using DS3 link. We are both using Cisco Router with different model and also with different Network Modules. France Telecom is using 7613 and we are using 3825.

France Telecom uses PA-2T3 and we are using NM-1T3/E3 NM. However, when we are about to test our end-to-end testing, the serial interface is in "down" state and it is never going up. On the other hand, when I set it to loop back it is working and so I believe our network module is working. FT however, also did the same thing and their loop back also worked.

We are both using HDLC encapsulation and we have verified our parameters we have on both sides. Are we missing something?

Your kind reply and assistance on this matter is highly appreciated.


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Collin Clark Wed, 08/04/2010 - 12:43
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2 things to verify; framing and dsu bandwidth with the latter being the usual suspect. You could also hard loop at your end and see if it comes up at theirs and vice-versa. That will narrow it down to a configuration issue.

Hope it helps.

jesquibal Wed, 08/04/2010 - 12:54
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Thanks much, Collin.

Maybe we have some issue in framing. Below is the configurations we both have and I can see the "framing bypass" which is not available in 3825. The only option that I have in framing is c-bit and m23. Could this be the problem that hinders our routers to see each other?


interface Serial1/0

ip address

no ip redirects

no ip proxy-arp

no ip route-cache

dsu bandwidth 44210

crc 32

no cdp enable



interface Serial3/0/1

ip address

no ip redirects

no ip proxy-arp

dsu bandwidth 44210

framing bypass

cablelength 450

crc 32

no cdp enable


Thanks much.

Collin Clark Wed, 08/04/2010 - 13:45
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Here in the US we use C-bit, but I honestly have no idea what they use in France. It looks like you can bypass framing or at least it's in the config guide-

framing (E3 controller)

To specify the type of framing used by the E3 controller, use the framing command in controller configuration mode. To restore the default framing type, use the no form of this command.

framing {bypass | g751}

no framing

Syntax Description

bypass   Specifies that G.751 framing be bypassed.

g751   Specifies G.751 as the E3 framing type. This is the default.

tprendergast Wed, 08/04/2010 - 14:10
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It looks like the NM1-t3/e3 should support bypass framing. Can you post part of your config?

From http://www.cisco.com/en/US/docs/ios/interface/configuration/guide/ir_clear_channel.html#wp1064826

1. enable

2. configure terminal

3. card type e3 slot

4. controller e3 slot/port

5. framing {bypass | g751}

6. clock source {internal | line}

7. exit

Please provide a show controllers for both sides as well, or at least cut and paste the controller section of your config.



jesquibal Wed, 08/04/2010 - 14:21
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Thanks for the great info Collin.

Tim, please see below:

C-ISO-BDR(config-controller)#framing ?

  c-bit  C-Bit Parity Framing

  m23    M23 Framing Format

Btw, here's the version:
ROM: System Bootstrap, Version 12.4(13r)T11, RELEASE SOFTWARE (fc1)
C-ISO-BDR uptime is 2 hours, 17 minutes
System returned to ROM by reload at 19:04:59 UTC Wed Aug 4 2010
System image file is "flash:c3825-ipbase-mz.124-7d.bin"
Cisco 3825 (revision 1.2) with 226304K/35840K bytes of memory.
Processor board ID FCZ1330704G
2 Gigabit Ethernet interfaces
1 Serial interface
1 Subrate T3/E3 port
and the show controllers
C-ISO-BDR#sh controllers T3
T3 1/0 is down.
  Applique type is Subrate T3
  Transmitter is sending remote alarm.
  Receiver has loss of signal.
  MDL transmission is disabled
  FEAC code received: No code is being received
  Framing is C-BIT Parity, Line Code is B3ZS, Clock Source is Internal
  Data in current interval (160 seconds elapsed):
     0 Line Code Violations, 0 P-bit Coding Violation
     0 C-bit Coding Violation, 0 P-bit Err Secs
     0 P-bit Severely Err Secs, 0 Severely Err Framing Secs
     160 Unavailable Secs, 0 Line Errored Secs
     0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
  Total Data (last 9 15 minute intervals):
     0 Line Code Violations, 0 P-bit Coding Violation,
     0 C-bit Coding Violation, 0 P-bit Err Secs,
     0 P-bit Severely Err Secs, 0 Severely Err Framing Secs,
     8100 Unavailable Secs, 0 Line Errored Secs,
     0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
tprendergast Wed, 08/04/2010 - 14:49
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In Europe, they almost always deliver E3 in my experience.

Try doing this:

conf t

card type e3

controller e3

framing bypass

clock source line


I think you set up the controller as T3 instead of E3. Did you confirm with the ISP that they are controller T3 and not E3?

jesquibal Thu, 08/05/2010 - 07:48
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Hi Tim,

Yes, it is T3. Any suggestions please?

Totally lost...

tprendergast Thu, 08/05/2010 - 07:56
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If it is T3 on both sides, then you need to have the ISP change from "bypass framing" to one of the two options available to you: m13 or cbit.

You must have those match on both sides. Give that a shot.

jesquibal Thu, 08/05/2010 - 09:13
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For everybody's benefit... we are able to make it work!

HDLC encapsulation for some reason is not working. Instead, we ended up using PPP encapsulation, m23 framing, crc 32 and no cdp enable.

Thanks Collin and Tim for your kind support!



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