Unknown MAC address

alan.morris · ‎09-16-2009

We have installed a 526 Wireless controller and 520 express switch. As far as we can tell all is configured ok. We use wpa/enterprise with Radius server an clients authenticate OK and get an IP lease from our windows (SBS) dhcp server. Unfortunately we cannot ping this server, but we can ping all other computers on the network. The reason seems to be that we get a rogue mac address for the server's IP. If we wireshark it we see the server initially replying to the ARP WHO HAS correctly followed by another from a ASKYCOM device. This MAC then appears in the 520 gigabit uplink's mac table.

If we look on the network to which the 520 is connected this MAC address does not appear, so it seems as if it is being generated within the wireless system!

Anyone have any ideas?

sbyrnes · ‎09-21-2009

Is it possible to configure a static ARP entry on your switch for your SBS?

alan.morris · ‎09-21-2009

Hi thanks your response. We have tracked the issue down (we think/hope!) to a rogue (with duplicate IP) on the wired network.

If we cleared the arp cache and pinged the server IP address (192.168.0.1) we get a good reponse to the ARP "whohas" followed by another from the rogue. However when on the wired side this seemed to have no effect and indeed the switches did not contain the rogue MAC address in their MAC address table, when on the wireless side it did cause a problem! We think it might be down to a user installed low cost switch using the common address we unfortunately selected for our server.