when i patch my XP laptop (with a Cisco VPN client installed) into any Cisco device i can ping the Cisco device from my laptop but cannot ping the laptop from the Cisco device.
i noticed this when trying to update the ios on a catalyst 6500 - couldn't use the tftp server on the directly connected laptop.
got round this eventually by disabling the Cisco VPN service on the XP laptop - then i can ping the Cisco device form the laptop and vice versa. tested this with various Cisco VPN clients and platforms and the results are the same.
done a packet capture on the laptop when pinging from the Cisco device and it shows nothing until i disable the Cisco VPN service on the laptop - the packet capture then shows a packet from the Cisco device to the Cisco CDP multicast address 01-00-0C-CC-CC-CC and then the laptop starts replying to the echo requests.
i now know how to 'resolve' this but can anyone tell me what is actually happening when i have the VPN client service enabled.