WS2008R2 - Network Load Balancing and IIS - I have no idea

I'd like to avoid discussion of IIS ARR for now - it isn't essential to get NLB working.

I have two computers (both in the same domain, btw) who are connected to two networks:

• A private internal network that the AD domain lives on. 192.168.0.10 and 192.168.0.11 respectively. This network has no default gateway.
• The public Internet. 123.123.123.10 and 123.123.123.11 respectively.

I'd like both servers to participate in an NLB cluster to serve a series of web applications that will keep on running even if one of the servers goes down (Windows updates, hardware failures, etc).

I've installed the NLB role on both computers and set up a cluster on the public (123.123.123.xxx) adapters and set the cluster to use a new IP address 123.123.123.12.

The cluster is in Multicast mode. I understand that Unicast mode causes ARP flooding and also prevents the "public" adapter from being used for anything besides NLB tasks (I would like to keep some applications on a single server and I can't install a third NIC just yet, hence multicast mode).

The NLB manager says the cluster is "Converged" without any problems, and when I try accessing the public cluster IP 123.123.123.12 from each machine then the IIS Default webpage loads fine.

However when I try that IP address from my home connection it doesn't work - I get a TCP timeout.

Also, in IIS Manager when I go to Site Bindings the cluster IP address isn't listed. Nor does it appear when I run ipconfig /all which is strange because it appears in Network Adapter properties.

So my question is: why do I get TCP timeouts and why isn't the cluster IP appearing in IIS?

EDIT: When I ran ipconfig /all again, the cluster IP appears. Strange. Maybe I missed it originally?