Category Archives: NSX-T

NSX-T BGP Filter

There are three steps to creating BGP filters in NSX-T:

  • Create an IP Prefix for “ANY” and each tenant subnet.
  • Create a IP Route Map
  • Apply the Route Map to the T0 Router Uplink

IP Prefix

An IP prefix list contains a single or multiple IP addresses that are assigned access permissions for route advertisement. If there are multiple IP addresses in this list are processed sequentially. IP prefix lists are referenced through route maps with in or out direction.

For example, you can add the IP address to the IP prefix list and deny the route from being redistributed to the northbound router. This means that with the exception of the IP address all other IP addresses are going to be shared the router.

You can also append an IP address with less-than-or-equal-to (le) and greater-than-or-equal-to (ge) modifiers to grant or limit route redistribution. For example, ge 24 le 30 modifiers match subnet masks greater than or equal to 24-bits and less than or equal to 30-bits in length.

The default action for a route is Deny. When you create a prefix list to deny or permit specific routes, be sure to create an IP prefix with a blank network address and the Permit action if you want to permit all other routes.


  • From your browser, log in to an NSX Manager at https://nsx-manager-ip-address.
  • Select Routing from the navigation panel.
  • Select the tier-0 logical router.
  • Click the Routing tab and select IP Prefix Lists from the drop-down menu.
  • Select Add.
  • Assign a name for the IP prefix list.
  • Click Insert Row to add a network address in the CIDR format. For example,
  • Select Deny or Permit from the drop-down menu. You grant or deny each IP address from being advertised, depending on your requirement.
  • (Optional) Set a range of IP address numbers in the le or ge modifiers.
  • Click Save.
  • The newly created IP prefix list appears in the row.

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NSX-T – Physical Requirements

I’ve been really lucky over the last few weeks getting to do some deep dive workshops¬†on NSX-T and will be blogging a lot about the good the bad and the ugly over the next few weeks (really good timing for “Blogtober” right?!)

First things first the documentation, for the moment at least, is a little bit on the light side. VMware are obviously working on the documentation as I am starting to see some more become available in the public domain but it certainly wasn’t as well documented as other GA products.

This leads onto my first topic, as I think it’s quit a big one!

I’m going to post about the new routing and switching technologies/methodologies used in NSX-T as they are VERY different from NSX-V in the next few days but for now let’s assume there is a need to move away from the well known and loved Distributed Switch (start looking up the¬†Opaque Switch). Put simply you can’t run a vSphere Distributed Switch on a KVM host, the price for delivering a Hypervisor agnostic SDN solution means we need to introduce a new type of virtual switch.

No big deal right?

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