Simon Krenger

When I tried to run a scan with NMAP over my VPN connection, I received the following error:

PS C:\> nmap -sP 192.168.10.0/24
Starting Nmap 5.21 ( http://nmap.org ) at 2010-11-18 09:35 W. Europe Standard Time
nexthost: Failed to determine dst MAC address for target 192.168.10.0
QUITTING!

Alright… A quick search with Google revealed the following topic: http://seclists.org/nmap-dev/2008/q1/81.

So to get it working, perform the following steps:

1. Open a console and type

   ipconfig /all

   Then look out for your VPN Adapter. Usually, the description of your adapter contains a line similar to this: “Cisco Systems VPN Adapter for 64-bit Windows”. For the next step, write down the MAC address (“Physical Address”) and the IP address (“IPv4 Address”).

2. With this information, create a new static ARP entry:

   arp -s <IP> <MAC>

   e.g.

   arp -s 10.150.0.41 00-00-00-00-00-00

   This will create a static ARP entry for your VPN adapter. Note that creating a static ARP entry can create a whole set of new problems with your network configuration!