Explain Transparent mode in monitor

The transparent mode is explained here

To monitor internet link, behind local router pool members, create a icmp monitor with alias address an external IP address (ex : 8.8.8.8) and transparent enabled.

For each pool member, it will request ARP of pool member (ex: result 00:01:02:03:04:05) and send a icmp packet with

• destination address 8.8.8.8
• destination MAC 00:01:02:03:04:05
• source address the IP address on same subnet than pool member

If no response, the pool is marked down

Panki, let me put it in other words for you.

A transparent monitor is used to test the transparency functionality of a specific device - normally a firewall. The device is marked down, if it's not transparent. Though one condition is that the device you are testing for transparency is directly connected - i.e. on the same broadcast domain with the F5BIGIP appliance. Another thing to keep in mind is that the transparent option is not available on all monitors. Generally speaking, it's available on all reachability type monitors.

Here is an example:

Topology: ROUTER ---- FIREWALL ----- F5

FW is a pool member.

You need to test if ROUTER is reachable through the FIREWALL; if not, FIREWALL should be set as down.

In this case, you may think you could setup the ROUTER as a node and give it an icmp monitor. But this won't be testing the status of the actual FIREWALL.

You need to setup a transparent monitor with the IP address of the ROUTER and assign the monitor to the FIREWALL pool member.