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New Member

ATM over NM-1 T3/E3

Tried with AT&T last night for 3 hours trying to bring up a DS3 ATM circuit.

Found limitations with the NM-1T3/E3 as follows:

1. c-bit framing is limited to "plcp" only. No "direct" option.

2. VPI/VCI threshold limitation VPI (0-15) and VCI (0-63).

Anyone get this card to work with ATM?

I could get an up/up status, but every packet is aborted (CRC errors). Also, AT&T never synched up in framing.

See config below:

Cisco 2811 running 12.4(3a)

Interface hardware = NM-1 T3/E3

card type t3 1


ip cef


controller T3 1/0

clock source line


interface Serial1/0

ip address

encapsulation atm-dxi

no keepalive

dsu bandwidth 10000

dxi pvc 1 41 mux

dxi map ip 1 41 broadcast



Re: ATM over NM-1 T3/E3


DXI is a standard used for carrying ATM cells over serial interfaces. AFAIK, you cannot use this type of interface if the interface at the other end is a standard ATM interface.

I would think that's why your link is not coming up. You really need to use something like NM-1A-T3, which will provide you raw ATM capability. The other option is to use an ATM data service unit (DSU) which will convert the DXI frames into native ATM before transmitting them to AT&T.

Hope that helps - pls rate the post if it does.


New Member

Re: ATM over NM-1 T3/E3

Yea, that's what my research tells me as well.

Without an ADSU upstream to strip headers and reformat data this thing is useless for ATM.

No idea why Cisco gave this encapsulation ability to this interface. It's very limited, if not useless.

Thanks for the response.