Solving asterisk´s HDLC Abort Issue

Have you encountered the following msgs in your /var/log/asterisk/messages?

Oct 23 16:54:51 NOTICE[3345] chan_zap.c: PRI got event: HDLC Abort (6) on Primary D-channel of span 1
Oct 23 16:54:54 NOTICE[3345] chan_zap.c: PRI got event: HDLC Bad FCS (8) on Primary D-channel of span 1

if so... you've come to the right place. This is a very tricky one. There are mailing lists with tons of messages regarding this issue scattered throught the web, but none of the them actually follow throught what causes this and how to solve it.

The tricky part is that you system may probably seem to work, you can receive and place calls, but every now and then... all of the calls get dropped at the same time. "Must have been a quirk" you say to yourself even though you know such thing does not exist. Then a few minutes afterward... again. And that YELLOW alarm is now staring you in the eyes with that smug in his face....

PRI configuration is not for the faint of heart, that is for sure. But this message 99 times out of hundred is a harware incompatibility issue, not ISDN config.

High-Level Data Link Control or HDLC is a bit-oriented synchronous data link layer protocol, HDLC was introduced into Digium systems in order to allow data and voice to be used/routed in the same card. This is a good thing, the bad thing is that it relies on more on the system clock for timing. And new motherboards and kernels do not play nice with this settings and old telephony cards.

This may be caused due to IRQ interrupt sharing, APIC, HD params, but to put it plain and simple: YOUR TELEPHONY CARD DOES NOT LIKE YOUR MOTHERBOARD. I wish i had seen that sentence a few months ago.

This was exactly the case with my Proliant ML150 G3 server, which has an Intel Motherboard and specially an Intel Onboard ethernet card. I had a TE110p, which has been my workhorse in several other settings, so it was strange for me that it failed on me so often. As it turns out, Digium's TE110P is the picky girl type, it does not play well with others because of its chipset (TigerJet). Digium was aware of this, so they had to go back to the drawing board and came up with what they like to call "VoiceBus Technology" which basically works a whole lot better.

So here it is, plain and simple if you have a TE110P card having this problems, you MUST update your card to a newer version or get a motherboard that works with that TE110P and hold on to it, hard. They are getting harder to find by the minute. So the solution: Buy a TE120P with the new VoiceBus technology or just run to the Sangoma Camp.


I wish i had a magical bash script that solved this issue... but this time you must take the expensive road.

Luckily you may have found this blog very early in the guessing process of solving this issue and saved a ton of time. Trust me, i was seconds away of trying voodoo or any other sort of black magic.


Hope this helps!


Alex