Re registering users without resetting asterisk

is there a command to have the sip devices re-register, ive got some cheap ata’s that i have to turn off and on after awhile because they time out, coule be a nat issue or something, but in the meantime i need to be able to kick them out so they try to reregister, thanks. By the way the boxes are Wordaccxx, and under the users i have nat=yes under sip.conf.
Thanks in advanced.

in sip.conf also turn on for them qualify=yes. This will avoid the issue of nat mappings expiring (which causes them to go unusable). Qualify sends a sip packet to the device every minute or so and measures the response time for the reply. It also functions as a ‘keepalive’.,
also set defaultexpirey= and maxexpirey= to be lower numbers. They state (in seconds) what the default and max registration expire time is. For a NAT environment maxexpiery shouldnt be more than about 300 (5 minutes). default at 60 should solve many problems, although it will generate a lot of console traffic for phones re-registering

hope that helps.

Yep, i think this solved the issue with the timing out. thanks!!!