First, I would do a ps -aef |grep bootpd to see how the command is running. Next, to keep the file from growing, I believe you can send the output to /dev/null by linking the file there, as follows.
ln -s /var/adm/messages /dev/null
When you eventually fix the problem, then remove the link.
Now, I would read the man page for bootpd. It will tell you a great deal.
I wouldn't necessarily do this step, but you can to stop the messages. Next, if you choose to you can edit the /etc/inetd.conf file and comment out the line for that. Also, in /etc/services.
OR you can kill and restart the bootpd daemon if you need it to be running.
ps -aef |grep bootpd |grep -v grep
kill PID # for bootpd
/usr/lbin/bootpd -s
Try these steps and get back...