E1 line debug L1/L2

Hello all, Brief question. Is it possible to debug E1 line by connecting it to the 2nd port of the same NIC making a wired loop? Is it enough to open->ioctl->read from /dev/dahdi/channel to get a stream of LAPD SABME messages transmitted by BSC? A bit more details for those interested I'm still trying to bring up BTS Nokia Flexi with OSMO-BSC. I'm using an E1 card Digium TE405P on the server side. OSMO-BSC is connected with Nokia BTS via a single E1 line. Looks like on Level1 everything is ok because BTS can detect the link and raise an alarm if the wire is getting disconnected. I can observe some data from timeslots on BTS side and if some channel is configured as D-Channel in /etc/dahdi/system I see transmission of block "01111110". But the problem is that LAPD link is not establishing. I can't find any tries on BTS side and BSC does not receive anything from BTS, just set of SABME messages in PCAP file. T200 expires and so on. I tried various T200 values. So, now it looks for me like L1 does not receive anything from L2 on BSC side and nothing is transmitted over the wire to BTS. dahdi_tool shows status "OK" So, my nearest plan to check data transmission over wired loopback. Thank you Babanov Ivan