WAN Impairment/WAN Emulator with WAN Bridge

WAN Impairment/WAN Emulator with WAN Bridge

Playing in the lab and want to impair a link with delay or loss?  🙂    I use WAN Bridge – its simple and free.


So say I’m testing an SD-WAN brownout/impairment avoidance solution in my lab.  For example, Cisco’s IWAN.  I’m going to need something to impair links with delay or loss.  I like WAN Bridge.  Why?  Because its simple, easy, and free.


There has been one thing I’ve struggled with in the past year about.  Every time I needed an impairment point this burned up 2 NICs on my UCS equipment.  Why? Cause I couldn’t seem to figure out how to load one NIC on a UCS as a trunk port with multiple VLANs on it and have multiple WAN bridges with just 1 trunk on a switch.

So that meant, for a recent CPOC that I was doing, if I really wanted 6 impairment points (red circles in diagram below) I was going to need to eat up 12 NICs on my UCS.


There had to be a better way…..

My friend, David Prall, was convinced it “should” work. I was equally convinced that I had tried it before and I must be “hitting some issue” with WAN Bridge.  Oh… and if you don’t know David Prall he is just majorly brilliant and is usually right.  So yeah… there was a way.  We used 1 NIC on the UCS. Trunked all 12 vlans below. And connected them up to 6 WAN Bridge VMs.  🙂


  • Make sure you disable spanning tree on the switch for all of the VLANs that you are using as WAN Bridge impairment points. Otherwise spanning tree will get broken and you wont forward on the port.

Here is a 12 minute YouTube video. 🙂   Have Fun!

ISO   <– ISO Image.


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