How to use the ISP Redundancy Feature of Forefront TMG [3. Update]
The ISP Redundancy Feature of Forefront TMG 2010
Enabling Internet Service Provider (ISP) redundancy on TMG 2010
TMG 2010 ISP Redundancy
TMG 2010 ISP Redundancy issues
Make sure you have installed all relevant SP1 Rollups in right order.
And if you use ISP-R with no equal connections bandwidth, make sure you adjust the ‘Automatic Metric’ settings correctly and manually on the Advanced Properties for the Internet Protocol on your NIC used for ISP-R.
Usually it is always recommended to disable all offload capabilities on NICs and TCP/IP settings. But if you use different NICs with no equal offload capabilities is not recommended. Using equal NIC vendor and model for ISP-R is recommended.
Instead of changing the metric on the network adapter properties, edit the routes of both ISP connections for the default gateways on TMG and adjust the metrics there.
Go to ‘Network’ and on the right select the ‘Routing’ tab. In the right pane ‘Routing Tasks’ select ‘Create Network Topology Route’ and add your default gateways for each of your ISP connections with the relevant metric.
Watch the default IP address scenario in regards of new Enhanced NAT (ENAT) described here
Sometimes L2TP clients on your LAN will not be able to connect to L2TP gateways on the internet. You need to add a static route to your TMG network configuration to route through a specific WAN interface to the L2TP gateway.