During the test of some AR18-31, the topology is simple. Ar18-31 ADSL interface is connected with BRAS of the partner through ATM switch. After PPPoE configuration is finished, AR18-3 pings BRAS of the partner and PPPoE session is frequently up and down.
AR18-31 indicates that PPPoE session is up and down.
1. Check AR18-31 configuration. Compare it with typical configuration and there is no error.
2. Check AR18-31log and there is some alarm information. The alarm information displays that ATM (ADSL interface) interface of AR18-31 is up and down frequently.
3. Check configuration of ATM switch and there is no error.
4. Check configuration of opposite BRAS ATM. The default AAL5 encapsulation is AAL5SNAP and it is not consistent with AR18-31. Configure "encapsulation aal5snap" at ATM interface and the problem is solved.
PPPoE session is up and down. It indicates the physical layer is problematic. Link layer may be problematic. Check configuration of link layer protocol. Check whether the parameter matches or not.