A network tap is a device that provides a way to access data flowing across a computer network. Tap mode deployment allows you to passively monitor traffic flows across a network by way of a switch SPAN or mirror port.
The SPAN or mirror port permits the copying of traffic from other ports on the switch. By dedicating an interface on the firewall as a tap mode interface and connecting it with a switch SPAN port, the switch SPAN port provides the firewall with the mirrored traffic. This provides application visibility within the network without being in the flow of network traffic.
By deploying the firewall in tap mode, you can get visibility into what applications are running on your network without having to make any changes to your network design. In addition, when in tap mode, the firewall can also identify threats on your network. Keep in mind, however, because the traffic is not running through the firewall when in tap mode it cannot take any action on the traffic, such as blocking traffic with threats or applying QoS traffic control.
To configure a tap interface and begin monitoring the applications and threats on your network:
- Decide which port you want to use as your tap interface and connect it to a switch configured with SPAN/RSPAN or port mirroring.You will send your network traffic from the SPAN destination port through the firewall so you can have visibility into the applications and threats on your network.
- From the firewall web interface, configure the interface you want to use as your network tap.
- Selectand select the interface that corresponds to the port you just cabled.NetworkInterfaces
- SelectTapas theInterface Type.
- On theConfigtab, expand theSecurity Zoneand selectNew Zone.
- In the Zone dialog, enter aNamefor new zone, for example TapZone, and then clickOK.
- Create Security Profiles to scan your network traffic for threats:
- Select.ObjectsSecurity Profiles
- For each security profile type,Adda new profile and set the action toalert.Because the firewall is not inline with the traffic you cannot use any block or reset actions. By setting the action to alert, you will be able to see any threats the firewall detects in the logs and ACC.
- Create a security policy rule to allow the traffic through the tap interface.When creating a security policy rule for tap mode, both the source zone and destination zone must be the same.
- Selectand clickPoliciesSecurityAdd.
- In theSourcetab, set theSource Zoneto the TapZone you just created.
- In theDestinationtab, set theDestination Zoneto the TapZone also.
- Set the all of the rule match criteria (Applications,User,Service,Address) toany.
- In theActionstab, set theAction SettingtoAllow.
- SetProfile TypetoProfilesand select each of the security profiles you created to alert you of threats.
- Verify thatLog at Session Endis enabled.
- Place the rule at the top of your rulebase.
- Committhe configuration.
- Monitor the firewall logs () and theMonitorLogsACCfor insight into the applications and threats on your network.