An old battle; Cisco 877 with BT ADSL2+

Last week I had the missfortune of needing to get some low bandwidth endpoints online for a client, these unmanned locations would have a few peices of technology sat behind an ADSL router with an IPSEC VPN back to a central location,bog standard stuff!

Naturally, I’d specified Cisco 877 ISR routers (as anything newer was overkill) allowing a good level of remote management, monitoring and control.

Base configuration was written offline, router is then connected to a BT ADSL2+ socket and an issue I immediatley recognised reared it’s ugly head;

Errors would repeat every 30 seconds to 5 minutes, nearly two years on, 877’s still don’t support BT’s ADSL2+ connections it seemed!

Expecting a new, working ADSL firmware update in that timeframe, I headed to the website and was bitterly dissapointed, even the firmware release ‘patch’ of yesteryear had been removed (which we didn’t have much luck with anyway when it first came out).

I knew we were looking for at least (or 4.0.18 depending on where you see it written), backed up by many sources (just search for ADSL2+ BT Cisco 877).

What’s clear however, is that as talked about all over the place doesn’t seem to be solving anyones problems and after getting hold of a copy by searching google for the what the filename would be based on the download ( ) I once again confirmed this, even setting the line type to only ADSL2+ to rule out any negotiation issues still saw consistent drops every minute or so;

conf t
int atm0
dsl operating-mode adsl2+

(At this point it is probably worth mentioning that the 877 will use new firmware as long as it is called ‘adsl_alc_20190.bin’ and is found in the routers flash on startup (if not, the default firmware in the IOS will be used), further details and screensots courtesy of here!)

Eventually, after a lot of firmware testing, I found that cisco have some ‘by request’ only firmware versions which not many people seem to know about.
After testing internal version 4.0.223, I can confirm that my ADSL2+ link suddenly became stable and has continued this way ever since (Now over one week).

I think it’s a little strange that Cisco has kept this one so tightly under wraps.
Anyway, I am not suggesting that this firmware is fit, safe or even sensible to use, but it has resolved my issues here and if you’re reading this and at the very end of your patience with an 877/ADSL2+ combination, you can find the firmware at the link below;

I hope this helps! Let me know if you have sucess with this, would be interested to see how many people are still affected.