In this blog post, we will look at how to set up port mirroring on Juniper EX switches. The goal is to mirror all the traffic coming in and going out of one switch port to another port. By doing this, we can connect a laptop to the mirrored port and capture all the traffic. This is particularly useful when you can't directly capture traffic from a device, such as a CCTV camera, TV, or other similar devices. Let's get started.
In this example, we have a database server connected to port ge-1/0/1, and we want to mirror all traffic going in and out of this port to port ge-1/0/4, where our laptop is connected. With this setup, we can use Wireshark on the laptop to capture the mirrored traffic.
configure
edit forwarding-options
edit analyzer my_capture
set input ingress interface ge-1/0/1
set input egress interface ge-1/0/1
set output interface ge-1/0/4
commitThe ingress and egress parts of the configuration refer to the traffic coming into the port (ingress) and leaving the port (egress). Ideally, we want to capture traffic in both directions, but you have the option to mirror traffic in only one direction if needed.
If you want to learn more about port mirroring on Juniper devices, please refer to the official guide here.
