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PPP on ATM Throughput Issue


We currently buy services from a major Australian Telecommunications provider.

The services are an Ethernet over copper service which is then presented to us (a mini-ISP) as an ATM PVC. The service is marketed as a Bridged service (Pure Layer 2 end to end)

I am having some real strange issues here. I can get end to end connectivity working just fine. I have done several Tests.

The first test was to configure an ATM Sub Interace in bridged routing mode where I simply apply some IP addressing on in natively and have the client on the other end plug a LAPTOP into the their end and assign a correspondeing address on their end.

Here is the config of our end:

CISCO 7200 Series Router:

Cisco IOS Software, 7200 Software (C7200-ADVIPSERVICESK9-M), Version 12.2(33)SRE1


interface ATM2/0.49 point-to-point

description Customer-X-Link

ip address

atm route-bridged ip

no atm enable-ilmi-trap

pvc 0/49

encapsulation aal5snap


As you can see the VPI/VCI is 0/49 and when configured like this, the service performs very well.

However being an ISP ourselves we do not want to be configuring this service like this. We want to Transport this service as a Layer 2 service.

After trying to use l2transport by configuring AToM and Layer 2 Local switching with NO luck, I decided the best way would be to enable PPPoE on the interface and either terminate the service on our router or tunnel switch it elsewhere.

Here is how I have configured it. (it works) however I am having some kind of throughput issue when the customer is uploading (ie sending data towards my router).


bba-group pppoe BDAS

virtual-template 66


interface Virtual-Template66

mtu 1492

ip unnumbered Loopback10

no logging event link-status

peer default ip address pool melbourne

ppp authentication chap pap radius-group

ppp authorization radius-group

ppp accounting radius-group




interface ATM2/0.2 multipoint

description Upstream-Provider

bandwidth 150000

no atm enable-ilmi-trap

range BDASLite-EOC pvc 0/33 0/60

  dbs enable

  create on-demand

  protocol pppoe group BDAS


This all works however, for some reason I am seeing a throughput issue and I cannot do anything to make it better. The only way so far I can get good results is configuring the atm interface with the Ip addressing.

My question is: Am I missing something in my config that is causing me this grief.

What can I try?

Everyone's tags (3)
Hall of Fame Master

PPP on ATM Throughput Issue

If there is a performance problem, tha indicates packets are dropped or delayed somehere, and you should find where.

However for simplcity and performance reasons, many ISPs prefer bridged encap to PPP. That is also user preference.