plz help me i have problem to ping some of my computers. I have three computers with windows 7 , two computers with windows server 2003, two computers with cent os 5 and one computer with with windows xp. All these computers connected with cisco 3550 multilayer switch. All these computers have ipv4 connectivity.

I configure tunnel on cisco 2811 router. that is working fine. i have a /64 subnet. all computers can ping except one linux system and two server 2003 systems.

these three system can ping each others global scope ipv6 i assign them manually and also these system can ping there local link ipv6.

other two windows 7 windows xp and one cent os system can ping each other and also ping any ipv6 ip.

these four system are unable to ping other three systems local link ips. i assign them manully ips like ff::1/64 ff::2/64 and so on for testing. but all time 4 systems can ping each other and three systems can ping each other.