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25Jun/120

Configuring a port analyzer (port mirror) on the Juniper EX switch

Yes, it's been a while since my last update, so I'm going to make this one short and sweet. Lately I started messing around with Plex Media Center/Server and sharing my server with a couple of my friends. While I do have a good bit of bandwidth here at the house, my friends sure know how to suck that bandwidth dry. So, it's time to implement some traffic shaping here at the house.

In order to implement the traffic shaping, I need to know what the traffic looks like. For me to shape it, I need to know what it looks like, so I'm going to setup an analyzer. I have a specific media server that is separate from my lab rack. It's plugged into a little Cisco gigabit switch that has an LACP Lag bundle going back to my core EX3200-48T. To setup an analyzer is very simple...in fact, it's only 3 commands.

set ethernet-switching options analyzer plex–monitor input ingress interface ae0.0 set ethernet-switching options analyzer plex–monitor input egress interface ae0.0 set ethernet-switching options analyzer plex–monitor output interface xe-0/0/45.0

That's it. Now, let me explain what I did there.

To configure an analyzer called "plex-monitor" and specify the input (source) interfaces and the output interface, I need to configure the interface connected to my media server as input interfaces for the port-mirror analyzer. I want to see both ingress and egress traffic, so I tell it to do both.

[edit ethernet-switching-options]
user@switch# set analyzer plex-monitor input ingress interface ae0.0
user@switch# set analyzer plex-monitor input egress interface ae0.0

Now, I configure the output analyzer interface for the analyzer. This will be the destination interface for the mirrored packets:

[edit ethernet-switching-options] user@switch# set analyzer plex-monitor output interface ge-0/0/45.0

That's it. Now, all the traffic going to that lag bundle (the server is the only thing plugged into that switch) will be mirrored to port ge-0/0/45. I can plug my Wireshark box into that port, get a good capture of the traffic, and set my traffic shaping accordingly. Can you guess what my next post is going to be about? ;)

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