2.1.2.4 Fabric post-upgrade task

[JL421-Retired]

I just pushed out the 2.1.2.4 upgrade to one of our DNA-Center installs, and after the upgrade I am getting the following post-upgrade task when in a fabric site: 

• The fabric edge nodes do not need to reach each other using /32 in the underlay

And am presented with the option to Apply Changes. I don't see anything in the release notes or user guide mentioning this change, and am curious how traffic would get from switch to switch, without using the /32 RLOC address. What changes would this actually make?

[Jonathan Cuthbert]

On a currently provisioned Edge Node, please see the following output:

show running-config | begin ipv4 locator reachability 

ipv4 locator reachability minimum-mask-length 32
 ipv4 source-locator Loopback0
exit-router-lisp

I do not see the Apply Changes banner on my own current clusters, so I want to make sure we are talking about the same thing. 

If we are talking about the same thing, then the ipv4 locator reachability command would have an additional argument on the end of it after Apply Changes. 

[JL421-Retired]

If I run that command, the output you listed is the same output I'm presented.

If I look at that command, the only extra configuration that can be added would be "proxy-etr-only". I guess if that would be the change made, that would follow with the message the banner is displaying, and shouldn't be an impactful change. If you aren't seeing the banner in your own cluster, I'm curious what the trigger to display that message is, as I'm also not seeing it across all of my clusters either.

I'm adding a screenshot of the banner just in case we're talking about different things for some reason.

[Jonathan Cuthbert · Accepted solution]

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@JL421-Retired wrote:

If I run that command, the output you listed is the same output I'm presented.

If I look at that command, the only extra configuration that can be added would be "proxy-etr-only". I guess if that would be the change made, that would follow with the message the banner is displaying,

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Correct.  The proxy-etr-only argument would be added to the end of the LISP readability command on Edge Nodes for a given site.

show running-config | begin ipv4 locator reachability 

ipv4 locator reachability minimum-mask-length 32 proxy-etr-only
 ipv4 source-locator Loopback0
exit-router-lisp

ipv4 locator reachability <arguments>

This command configured the conditions that must be met for a routing locator (RLOC) (the Loopback 0 interface of another LISP speak device in an SD-Access network) to be treated as being reachable. 

ipv4 locator reachability minimum-mask-length 32

This command says that in order for an Edge Node 1 to send packets to another SD-Access Fabric node (Edge Node 2 for brevity), Edge Node 2's Loopback 0 must be present in Edge Node 1's global routing table as a /32 entry (host route).  It has been provisioned on Edge Nodes for some time now. 

ipv4 locator reachability exclude-default

This command has been provisioned on Border Nodes since day 1.  It says that for the Border Node 1 to send packets to another SD-Access Fabric Node (Remote Border 3), that device's Loopback 0 must be present in Border Node 1's global routing table as an entry of any length.  As long as Border Node 1 does not use a default route to reach Remote Border 3, it is considered reachable (from the perspective of LISP communications).

Putting it all together:

 ipv4 locator reachability minimum-mask-length 32 proxy-etr-only 

From the perspective of the Edge Node, the Border Nodes (External-Only and Anywhere | proxy-etr) must be present in the global routing table as a /32 entry.