I have a RB2011 iL;IN with firmware 6.34.3, and everything was working fine until today.
Suddenly, some machines were unable to connect to Internet.The only log I get is lots of:
Jun/14/2017 16:15:23 memory ipsec,error phase 1 negotiation failed due to time up: 127.0.0.1[500]<=>0.0.0.0[500] followed by a 16 hex char string:0000000000000000
This 16 hex string changes all the time.

What is the meaning of this error?
Might this be the origin of the problem I am facing?

Thank you
Rui

It's trying to establish IPSec connection. Did you configure something in IP->IPSec?

Thanks for your reply.
On that router I have a VPN with IPSec tunneling, but it was not changed recently.
What I found out is that I was using the usual Google DNS (8.8.8.8, 8.8.4.4) and it was down during Wednesday afternoon causing this error message.