Freebsd 5.0 NICs issue

[Amandeep Pannu]

Hi

I have a machine running FreeBSD 5.0 , it is actually my Primary DNS server.
it has two Nics.
em0 and em1
Now the em0 nic is up with 205.229.165.4 netmask 255.255.255.0

When I try to do
ifconfig em1 inet 205.229.165.8 netmask 255.255.255.0 up
it say File exists.
then i read that the netmask should be 255.255.255.255 then i did that the
machine then is hooked wiht the ethernet cable in em1 and it starts puring
some
kernel:arp messages.
I have tried doing it from scratch removinf all entriedsfrom /etc/rc.conf
and then tried to manuall assign them IP. em0 goes well but again em1 say
file exists or those arp messages copme up.

Any ideas what is going on.

Thanks in advance
A