Adding a route for a particular host

Details of connectivity :
Host : host1  (runs xen)
Guest : guest1 (runs under host1 xen server).

Host :host2 (different host on the nework)

To be able to ping from host2 to guest1

On host2:
#route add -host guest1 gw host1

You can mention the IP address or host name both works.

Now  try pinging from Host2 to Guest1 !!