Router cannot see Hyper-V Guest MAC address

Question

Greeting,
I have been trying to build a server on Hyper-V, on a host running Windows Server 2012 R2, and a wireless adapter is used.
A virtual switch was created as external, connected to the host's wireless adapter.
The guest OS is Debian 7, and the problem is it's unable to use DHCP to connect to the internet.
I have to manually specific an IP address and the subnet mask in order to access the internet in the Guest OS, say 192.168.0.50. And I set port forward to this IP for external connection to the guest, but then sometimes I cannot connect; without doing anything
it restores the connection after a while. At the same time I am keeping the MSRDP connection to tthe host so the host has not lost connecting to the internet.
When the server on Guest is not accessible from the web, I can still connect to the server within the host machine by typing the lan IP of the guest: 192.168.0.50
On checking the router, I found that two IP address 192.168.0.50 (Guest OS) and 192.168.0.15 (Host) are sharing the same MAC address (of the wireless card). It means the MAC address of the Guest OS is not seen by the router, and I suppose this is the root
for the instability.
Would you have any ideas about the situation, and suggested solution?
Thank you.

Answer 1

An update to my issue:
Just realized the possible cause: the (freaking) router is dropping inactive machine.
Basically the DHCP issue is not solved, but it doesn't seem to be a cause after all, as long as I manually assign the IP it works, even having the  2 IPs with the same MAC on the ARP table on router. (Host connection drop has to be further investigated).
As I found that the loss of connection actually happens after a while I don't touch the web server on VM, the longer I leave it idle the more likely I cannot connect to it again. The situation is like a prolonged loading when trying to access a website,
where sometimes you can connect after a while, or you never.
What's weird is, if I somehow manage to connect to the idle VM server by multiple attempts, and that after I have restored the connection, I can reconnect to the server from another computer very quickly without any significant loading time.
On some quick searches, I found someone using Linksys router is suffering from a similar situation as I do:
http://serverfault.com/questions/522448/application-request-routing-on-a-hyper-v-guest-intermittently-stops
So what I can try are basically 3 ways 
-Change the router, not viable as I don't own it.
-Insert a wireless bridge in between
-Do something with Debian, making it periodically generate network request to the internet to keep the connection alive
Any ideas about my observation, and maybe possible solutions?
Thank you for reading.