My PlusNet ADSL connection has been rock solid for years. Last week, my connection started dropping randomly, sometimes several times a day and sometimes overnight. Network load wasn't a factor. Phone line tests showed no issues. PlusNet said they thought the problem was in my network. And sure enough, my router debug logs showed my router was terminating the PPP connection because the PPP peer had stopped replying to the router's LCP Echo requests. My router was therefore taking the connection down.
Suspecting a hardware issue, I swapped the modem out for a spare but the problem remained. On a hunch, I tried doubling the LCP Echo interval setting in the router. The link has now been up for several days with no drops whatsoever. Maybe a config change in the ISP network caused this change to be needed or maybe my LCP settings were too aggressive and it's just luck I've had no problems until now. I've no idea.
But this got me wondering. What are the recommended PPP LCP Echo settings for DSL connections. Any thoughts?
The PPP LCP defaults in the my router are:-
lcp-echo-interval 5
lcp-max-failure 6
lcp-echo-adaptive
The lcp-echo-adaptive setting means the router will only send new LCP Echo requests if no data is received from the peer since the last LCP Echo was sent. Thus my router sends LCP Echo requests more often when the connection is idle.
I doubled lcp-echo-interval to 10 and the connection is now stable.
My setup is an unlocked HG612, ADSL2, connected directly to a Ubiquiti Edgerouter-Lite which does PPPoE.