Just when I thought no vendor stupidity peculiarity could surprise me, Cisco IOS/XE proved me wrong.

I was improving a completely unrelated BGP functionality. I ran BGP integration tests on Cisco IOL (because it’s the fastest one to boot), and the BGP community propagation test failed. After verifying that I did not change the template and that the data structures had not changed, I checked the IOL release I was using.

Surprise 🎉🎉: the neighbor send-community configurations that worked since (at least) the IOS Classic release 15.x stopped working in Cisco IOS/XE release 17.16.01a.

Background Story

This is the help message offered by a Cisco IOS router for the neighbor send-community configuration command:

dut(config-router-af)#nei 10.1.0.1 send-community ?
  both      Send Standard and Extended Community attributes
  extended  Send Extended Community attribute
  standard  Send Standard Community attribute
  <cr>      <cr>

That’s super-annoying to implement in a configuration template when your data structure contains a list of community types that should be sent to a neighbor.

Purely by accident (one has to suppose), using two configuration commands gets the desired results:

dut(config-router-af)#neighbor 10.1.0.2 send-community standard
dut(config-router-af)#neighbor 10.1.0.2 send-community extended
dut(config-router-af)#do show run | include neighbor 10.1.0.2 send
  neighbor 10.1.0.2 send-community both

The neighbor send-community standard command followed by the neighbor send-community extended command magically results in neighbor send-community both. Mission Accomplished!

However, that no longer works in Cisco IOS/XE release 17.16.01a (even though it worked until at least IOS/XE release 17.15.01).

dut(config-router-af)#neighbor 10.1.0.2 send-community standard
dut(config-router-af)#neighbor 10.1.0.2 send-community extended
dut(config-router-af)#do show run | include neighbor 10.1.0.2 send
  neighbor 10.1.0.2 send-community extended

WTA*? The propagation of standard BGP communities is gone.

Considering all the fairy tales I’ve been hearing about how it’s impossible to change any ridiculous old setting in a major network operating system, I’d love to know what triggered this sudden “back to the 90s” stunt.