You just bought a brand new inline security appliance—a next-gen firewall, intrusion prevention system (IPS), data leakage prevention (DLP) system or web application firewall—and you’re ready to deploy it in your network. But then it sits in a box for months because you look at the network design and can’t decide where the new appliance will fit in.
The whole point of an inline security appliance is to actively analyze every bit, byte and packet® you send to it—let’s go over the keys to connecting your new inline security appliance for optimal network access.
If you want your security appliance to actively analyze network traffic, your first thought might be to place it right between the two network elements you want to monitor traffic for (for example, a router and switch). Resist this thought. The design would look like this:
Under ideal conditions, this design might seem effective—but it will cause major issues in your network, including:
We often discuss why SPAN ports are no longer an effective means of ensuring network visibility, but many customers still use them extensively. SPAN ports may have been effective enough when we were only analyzing 10Mbps links, but now they introduce a number of issues, including:
These are only a few of the problems that SPAN ports introduce when they are used as network TAP replacements. That’s why network TAPs are the best practice for in-band security appliance connectivity.
What do Palo Alto Networks and Cisco all have in common? They partner with Garland Technology as their network TAP vendor.
When you need to ensure 100% uptime and visibility for inline security appliances, a bypass network TAP is the only option.
With a bypass TAP you can configure and validate your inline security appliance off line. Once fully validated, you can be deploy them inline for active analysis. Another key feature is the ability to take the security appliance back off-line without interrupting network traffic for updates, maintenance or troubleshooting.
Network bypass TAPs have a variety of features—the key is to find the solution that meets your needs today and is scalable for tomorrow.
Bypass TAPs are not a one-size-fits-all solution. When purchasing a bypass TAP for your network, consider the following:
Bypass network TAPs are placed between the inline appliance and the router/switch links that they are taking traffic from. The router and the switch are plugged into Network Ports A and B and the inline appliance is plugged into Monitor Ports C and D, giving total visibility without introducing a point of failure. See the following graphic for an example:

Network TAPs aren’t one-size-fits-all solutions. If you want to ensure optimal network access for your new inline security appliance, you must understand your network specifications and purchase the appropriate bypass TAP.
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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.