SD-Access and E-911 Services

Peter Welcher
Architect, Operations Technical Advisor

This blog is part of a series covering various SD-Access topics.  

Previous blogs in this series: 

 There’s one key thing to consider in your SD-Access planning, something that might not be on your “radar, or that could be easily forgotten or overlooked: What does your organization do for E-911 location services? 

This blog covers what I know (or think I know) about E-911 and SD-Access.  

Disclaimer: I’m not a unified communications/collaboration guy. So I researched this topic as best I could, including discussions with colleagues. There may be other choices or factors I’m not aware of.  

My goal here is primarily to alert you that E-911 needs to be part of your SD-Access design planning. And sketch out what you can do within SD-Access to align with your E-911 solution.  

How Does E-911 Location Work? 

I gather there are two basic ways that sites and vendors make E-911 location work: 

  • Map phone subnet to location 
  • Map phone switch and port(s) to a location (phone MAC to switch/ports and that to a location via lookup) 

There may well be other methods. These two appear to be the common ones.  

Some E-911 products do the first of these. Cisco Emergency Responder, RedSky, and West can do the latter.  

What Can We Do In SD-Access? 

Normally in SD-Access, subnets carry traffic for all SGs in a given VN across all switches within a fabric site. That means that the subnet is not normally tied to, e.g., a wiring closet.  

That is fine for E-911, as long as your E-911 product bases the user location on switch and port.  

If the E-911 product uses a subnet to identify the location, note that you can deploy SD-Access with per-switch VLANs for either data or voice. The cost of doing so is a good bit a bit more clicking in DNAC when provisioning the switches. Do-able, but tedious.  

The way you can configure this is by going into Host Onboarding, going to Port Assignment, and assigning a VoIP IP Pool that is for the selected switches and ports. If you need to do E-911 for softphones, then you can also do a local over-ride for the data IP Pool.  


E-911 location services are something you need to think about when planning your SD-Access design and deployment. Two common approaches are discussed above. If your solution is subnet-based rather than switch/port-based, then you can either change to a product that uses switch/port mapping, or you can use per-switch IP pool over-rides in DNA Center.  

Other E-911 products may have different capabilities or limitations. Hopefully, this blog will provide you with options that can work with your situation.  



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