IP Issues - solved =D
I’ve been scratching my head for half a week on this one, and I’m happy to say I’ve finally solved it. I shan’t go through the problem in detail, as I have found a solution, linked below.
In short summary, I have a ThinkPad T61 running Windows XP SP3, and a MacBook Pro running Leopard. On both computers I have received IPs and other settings via DHCP. Both can access the internet fine, both can ping themselves under localhost and the assigned IP address. But the MBP couldn’t ping the XP machine, despite it working in the opposite direction. That is, despite the network connection seeming to be in order, and after having turned off Cisco Security Agent and Windows Firewall under “Services”, the XP machine never returned incoming ping requests. I had a glance at the raw network traffic using Wireshark (formerly Ethereal), but that didn’t reveal any incoming pings, although I didn’t spend too long trying to get it working, as I was beginning to wonder was it an issue with the corporate network.
The cause, as found in this useful post after a lot of searching, was my Cisco VPN Client. It had an option of “Stateful Firewall (Always On)” enabled. Switching it off solved all my problems =D So many thanks to a (possibly Irish) chap called Shane Burke.