I just found an answer, which works for me: through http://askubuntu.com/questions/344863/ssh-new-connection-begins-to-hang-not-reject-or-terminate-after-a-day-or-so-on; it looks like the issue is as...

Model : Hardware Version : Firmware Version : ISP : Like it says, the VR2600 is one of the routers that fails on what the openssh documentation describes as "A problem can arise when you are trying...