Fastest way to change IP addresses

Kevin Stevens kevin_stevens at
Tue Nov 18 14:27:31 PST 2003

On Nov 15, 2003, at 11:35, Jamie wrote:

>    I want to change the IP address from to
> on a FreeBSD machine as quickly as possible. Despite my efforts, I can
> only get the change to work by editing rc.conf and rebooting the 
> machine.
> Isn't there a more elegant way??

That *is* the elegant way.  You want a more expedient way.

>   In order to switch to I've tried:
> 1) ifconfig de0
>   ifconfig -a then gives me:
>   fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         inet netmask 0xffffff00 broadcast
>         ether 00:03:47:b1:d6:1c
>         media: 10BaseT/UTP status: active

That is not the correct broadcast address for that network...

>   But then I cannot ping the gateway,
>    ping
>   5 Packets transmitted, 0 packets received 100% packet loss

It should work.  Two thoughts:

If you've been bouncing around between addresses while testing, you may 
have confused the arp cache on the gateway device, which would need to 
be flushed or time out before speaking to you again.

When you make the IP change directly, it's then incumbent on you to 
also make any appropriate routing updates - this is handled 
automatically during boot by the rc.conf procedure.  Since you're 
changing addresses within the same subnet it shouldn't be a major deal 
(you shouldn't be attempting to route), but it should be checked 
anyway.  netstat -nr.


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