I have Cisco RV042 on both ends, running gateway-to-gateway VPN. It works well about on most days. On some days, such as today, RV042 shows VPN tunnel "connected" but I can't ping the other side. It looks as if Comcast is blocking IPSEC traffic.
I have tried power cycling everything. It doesn't help. It is very frustrating.
Most of the time, when this happens, it becomes normal the next day.