IP changed, then...

[Pei Hanru]

Hi,

I'm behind a NAT, running a Tor node. My ISP will unreasonably change my 
IP every 48 hours. Usually Tor runs well, but when my IP changes, I will 
get an entry in Tor log like this:

[notice] resolve_my_address(): Your IP seems to have changed. Updating.

Then:

[warn] second_elapsed_callback(): Your server (xxx.xxx.xxx.xxx:9001) has 
not managed to confirm that its ORPort is reachable. Please check your 
firewalls, ports, address, /etc/hosts file, etc.

The "[warn] second_elapsed_callback()..." is added to the log every 20 
minutes and will lasts forever. By contrast, if I restart Tor, then it 
tells me

[notice] Now checking whether ORPort xxx.xxx.xxx.xxx:9001 is 
reachable... (this may take up to 20 minutes -- look for log messages 
indicating success)
[notice] router_orport_found_reachable(): Self-testing indicates your 
ORPort is reachable from the outside. Excellent. Publishing server 
descriptor.

almost immediately!

So, should I restart Tor manually every time when my IP changes? In FAQ, 
I get an answer said no, but what's wrong here?

Hanru