>>> Set your SS7 trunk to SLC 1. I couldn't make it work >>> on SLC 0. No idea why. >>> >> >> The Taqua is 1 too? Regardless of Asterisk's setting, it shows the SLC 0. Setting the Taqua to 1 causes the F-Link to go down and Asterisk complains. >> > Yes. Both the taqua and the asterisk are set to SLC=1 > It looks like Asterisk pays no attention to the "slc" setting in chan_dahdi.conf, but instead libss7 (in ss7.c) automagically calculates the Signaling Link Code based on how many are linksets have been defined: /* ****************** */ // looks like we create a new mtp2 link and autoincrement the SLC counter m = mtp2_new(fd, ss7->switchtype); if (!m) return -1; m->slc = ss7->numlinks; ss7->numlinks += 1; m->master = ss7; if (zapmtp2) m->flags |= MTP2_FLAG_ZAPMTP2; ss7->links[ss7->numlinks - 1] = m; /* ****************** */ So changed it to add one (m->slc = ss7->numlinks + 1) and I'm getting MTP2 link issues: [Apr 30 16:01:04] WARNING[19051]: chan_dahdi.c:11509 ss7_linkset: MTP2 link down (SLC 1) MTP2 link up (SLC 1) [Apr 30 16:01:06] WARNING[19051]: chan_dahdi.c:11509 ss7_linkset: MTP2 link down (SLC 1) MTP2 link up (SLC 1) [Apr 30 16:01:09] WARNING[19051]: chan_dahdi.c:11509 ss7_linkset: MTP2 link down (SLC 1)