Each tunnel-group has its own DHCP server list (up to ten servers) and last viable server (last good server).
Hi,
When an IP address is requested and the last viable server is known, the ASA will traverse through the server list to find that server. If the server is still in the list, the ASA will start with that server. If that server fails, the last viable server for that tunnel-group is cleared and it will continue with the next server on the list until all servers are tried. The last viable server is set upon a server success.
When an IP address is requested and the last viable server is NOT known, it starts with the first server.
so it does not send request to both server at same time.
HTH
Abaji.
