ADSL problem on a 2651

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Oct 8th, 2008
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We currently have two customers both with Cisco 2651XM's configured with a standard ATM WIC card and ISDN BRI card. Both are connected to BT Wholesale provided IPStream MAX Premium DSL services. Both sites are running "c2600-advsecurityk9-mz.123-8.T3" as their IOS. The routers are both configured with PPP and Virtual Access 2 is currently up/down. The strange part comes when I do "sh dsl int ATM0/0". On the downstream the router reports the DSL using interleaving and on the upstream using fastpath. As far as I'm aware this is impossible but BTWS are saying the circuits are configured correctly and they can see no problems. Both circuits have also been rebuilt. Has anyone come across this issue before or know how to resolve it?

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Giuseppe Larosa Wed, 10/08/2008 - 13:21
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Hello Rob,

with DMT modulation different tones are used for upstream and downstream so this should be possible in theory.


try the following


term mon

debug ppp neg

debug ppp auth


int atm0/0

shut


no shut


and see if PPP negotiation starts if there is an exchange of frames

If you like you can post it here in a file


Hope to help

Giuseppe


Rob.D.Hamilton Wed, 10/15/2008 - 08:42
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Attached is the output from the routers log. As far as I can see it's not even trying to authenticate with BT Wholesale and I'm currently using BTWS' test login of [email protected]_domain. Even then they don't show any record of it. I'm really stumped.



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Giuseppe Larosa Wed, 10/15/2008 - 10:19
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Hello Rob,

there are only LCP packets sent by your router the O means tx I means rx. No LCP frame is received.

So or the encapsulation to be used is different : PPPoEoA instead of PPPoA or viceversa (so it was in another thread) or there is no PPP service on the link ( it is a line with classical IPv4 over ATM using aal5snap) or actually there is a L1 problem.


try to see the counters on the sh dsl interface check for total cells tx and rx and errors.

If statistics show a low error rate ask the provider what encapsulation they expect on the link

else ask the provider to verify the line.


Hope to help

Giuseppe


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