have an issue with my 2820N, i'm using Network load balance in server 2008R2 to flick mail/web traffic between my 2 mail servers for redundancy.

the 2 servers have individual Ip's and the NLB has the main IP.

svr1 - 0.12
svr2 - 0.11
NLB - -0.10 - all traffic is directed here. And switched between the above 2.

internally this is working fine,
Externally - when i configure the NAT to go to the NLB IP it works but when it switches to the other it fails, you can then reset the NAT in the router an it will work again until it switches? it like NAT is holding onto the MAC address of the 1 that was working and only releases it when you reset it?

a total pain because internal NLB is fine but it looks like it breaks and the servers are down because the NAT wont redirect to the new IP.