PPTP question

Recently set up PPTP on a W2K server (ip addy = xx.xx.xx.99) to
handle incoming, allowing callers to access the LAN. Had assigned
ip's xx.xx.xx.75 to xx.xx.xx.78 to PPTP callers.

Was doing a routine scan of the network tonight using ettercap
and it pulled up not only the W2K server on xx.xx.xx.99, but the
same MAC on xx.xx.xx.75. Nmap and SoftPerfect's Net Scanner,
the same. But, checking the router's settings revealed nothing
at xx.xx.xx.75.

I take it this is normal behavior for a PPTP server to pull an extra
ip address? Just want to be sure. Thanks.