ISP redundancy feature utilizes multiple ISP links and provide high-availability with load balancing and failover or just failover capability to the corporate Internet. The common functionality of ISP redundancy are:
- Designate primary and secondary link for internet connections
- Balance traffic load based on percentage of total traffic per link
- Automatic fail over to secondary link if primary link fails
Picture: ISP redundancy using FF TMG 2010
You must fulfill following requirements before you configure ISP redundancy.
- Two separate ISP links
- ISP provided Static IP must be obtain from separate subnet.
- Each network must have a Network Address Translation (NAT) relationship with the External network.
- To ensure that DNS requests are routed to the correct ISP, you must add a persistent static route for each DNS IP address(s) configured on the external network adapters
- Static NAT rules take precedence over ISP redundancy configuration settings. This means that a static NAT traffic directed to a primary ISP link is not rerouted to secondary ISP link if primary ISP link is down.
- you can designate traffic sent to a range of IP addresses is routed to a specific ISP link while configuring ISP redundancy. To do so, click Explicit Route Destinations>click Add Range. You can add multiple ranges.
To configure NICs which is connected to ISP Links
Right click on the external NIC connected to primary ISP>Click on Property>Select TCP/IP4>Click Property>Type the Static IP, Subnet Mask, Gateway and DNS provided by ISP
Repeat above steps for external NIC connected to secondary ISP Link. you will be prompted with the following warning. Don’t worry this is common phenomenon for windows operating systems when you add two gateway. Click Yes to save the configuration.
To add a persistent static route
Open command prompt as an administrator and add persistent route for both external NIC.
route -p ADD 192.168.1.254 MASK 255.255.255.0 192.168.1.254 METRIC 1 IF 3
route -p ADD 192.168.100.254 MASK 255.255.248.0 192.168.100.254 METRIC 2 IF 4
route [-p] ADD [destination] MASK [netmask] [gateway] METRIC [metric] IF [interface]
- P—-Makes the route persistent
METRIC---specifies the priority for this route. the route with the lowest metric has the highest priority.
IF---Specifies the interface number
To Verify NAT rule
Open Forefront TMG Management console, click the Networking node.
Click on Network Rules Tab>Check Network Rules
To Configure ISP Redundancy
Open Forefront TMG Management console, click the Networking node. In the details pane, click the ISP Redundancy tab> click Configure ISP Redundancy, follow the instructions in the wizard as shown on screen shots.
In this window, you can select preferred redundancy mode.
Apply Changes. Click Ok.
To modify each link. Select the link, Click on edit Selected ISP Connection. To monitor ISP redundancy, Click on Monitor ISP redundancy.