We know that In-Line (“Active”) network tools have become an essential part of any network. These appliances protect your network from various vulnerabilities, give you network visibility, and grant you access to a slew of services:
Vendors offer these services with active hardware/software packages that pick up your data and sift through it to find what they are programmed to find – and that is fantastic. What isn’t fantastic is that they add Points of Failure to your network if you install them as-is.
Last week, we touched briefly on what a network TAP is, and you saw how it doesn’t change or interrupt data – it just “copies” it, so to speak, giving you complete network visibility. Well, now we are taking that education and applying it! Specifically, we are exploring Bypass mode network TAPs – very powerful little pieces of hardware.
In-line appliances are active and installed directly between two network devices. This requires you to use a Bypass TAP that sends all of the network traffic through your In-Line Appliance. In addition to directing your traffic through the appliance, the Bypass TAP inserts a heartbeat into the in-line appliance – “sensing” the health of your monitoring tool. A note about this heartbeat – it is never inserted into the network; it is only present between the TAP and monitoring appliance.
Now, what happens if the appliance loses power, needs maintenance, or the heartbeat is lost?
This is the genius behind this device. It really is simple – if the appliance goes down or has to be updated, you can either stop the Bypass TAP from directing traffic to the device or it will do so automatically if it no longer senses a heartbeat. In either scenario, the bypass TAP keeps the network live, which would not have been the case had the appliance been placed directly in-line without the TAP. No more waiting for critical updates because it would disrupt your network visibility. No more network outages because an appliance went down. Once you are ready to include your device again, or the heartbeat is back in place, the TAP can begin directing traffic again.
Some manufacturers build a TAP or Bypass into their appliances – but companies that would want to totally remove the point of failure from the application realize that an external TAP is the clear winner here.
Learn more about the network TAP and how it improves your network management.
If the inline security tool goes off-line, the TAP will bypass the tool and automatically keep the link flowing. The Bypass TAP does this by sending heartbeat packets to the inline security tool. As long as the inline security tool is on-line, the heartbeat packets will be returned to the TAP, and the link traffic will continue to flow through the inline security tool.
If the heartbeat packets are not returned to the TAP (indicating that the inline security tool has gone off-line), the TAP will automatically 'bypass' the inline security tool and keep the link traffic flowing. The TAP also removes the heartbeat packets before sending the network traffic back onto the critical link.
While the TAP is in bypass mode, it continues to send heartbeat packets out to the inline security tool so that once the tool is back on-line, it will begin returning the heartbeat packets back to the TAP indicating that the tool is ready to go back to work. The TAP will then direct the network traffic back through the inline security tool along with the heartbeat packets placing the tool back inline.
Some of you may have noticed a flaw in the logic behind this solution! You say, “What if the TAP should fail because it is also in-line? Then the link will also fail!” The TAP would now be considered a point of failure. That is a good catch – but in our blog on Bypass vs. Failsafe, I explained that if a TAP were to fail or lose power, it must provide failsafe protection to the link it is attached to. So our network TAP will go into Failsafe mode keeping the link flowing.
Single point of failure: a risk to an IT network if one part of the system brings down a larger part of the entire system.
Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.
Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.