3 Com OC531 Authentication Problems

[Walshie]

I have a customer who accesses the internet (using PPP authentication)with his OC531.
To support this, I used to use another 531 (not using PPP authentication). However, I have had to replace this support router with a Cisco 1720 (this one uses PPP authentication) and now every time I connect, the customer can no longer access the internet unless he re-boots the OC531.
Any help would be appreciated.?

 

[Bloch]

I can't help but i'm interesting to know how to make Lan to Lan connection with 2 OC 531 because I don't success to do it only using the notice.

Sorry for my english and thank you very for your help