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7921 portables and CER

From the perspective of hard wired telephones the Cisco Emergency Responder is pretty cut and dry.

How have you all handled portable wireless telephones like a 7921 ?  Right now in my CER they show up as unallocated. Since they can travel building to building I am not sure the best way to deal with them.



Everyone's tags (5)
Cisco Employee

Re: 7921 portables and CER


The 7921 phones should be tracked via ip subnets, you must configure the subnet and then assign ERLs to the
configured subnets.

Please refer to the Admin Guide - See the section "Configuring IP Subnet-based ERLs"

Use IP subnet-based ERLs to locate and track 802.11b endpoints, such as Cisco Unified Wireless IP Phone 7920 devices
and Cisco IP SoftPhones running on 802.11b. Cisco ER cannot locate or track 802.11b wireless endpoints to a Cisco Access Point.
It is recommended that:

-You configure a subnet-ERL for each access point.

-You identify the switch port to which the access point is connected and you assign the 802.11b wireless endpoint to the subnet
ERL that is configured for that access point.

If you use Layer 3 (IP) roaming for wireless IP phones and/or wireless phones register using their Wireless Access Point's IP address,
then Cisco ER will not be able to automatically track movement of these phones. This is because Cisco ER uses the IP address of the
phone to determine the phone's location. Do not use Layer 3 roaming if you need Cisco ER to automatically track movement of wireless
phones in your network.


Teresa Stevens
Unified Communications PDI Team

Regards, Tere. If you find this post helpful, please rate! :)

Re: 7921 portables and CER


Do you know if there are any plans in the Cisco camp to provide a solution whereby customers can use layer 3 roaming and have accurate location information for CER? Particularly for customers that have bought into the whole "unified" concept with Cisco gear end-to-end.

Just curious because this question comes up a lot more recently and it appears to be a question that has been around for a few years.



HTH -Bill (b) (t) @ucguerrilla

Please remember to rate helpful responses and identify

Cisco Employee

Re: 7921 portables and CER

Hi Bill,

This question has been asked before and recently the BU answered that it is one of the highest priorities for CER to support adequate location
tracking of wireless IP phones. So yes, there are plans to support this, but there is no ETA as to when this feature will be available.



Regards, Tere. If you find this post helpful, please rate! :)

Re: 7921 portables and CER

For the record, that has been the BU answer for years. For those who run across this thread here are [sanitized] snippets of my issues with ER support of wireless voice networks. I would consider these very carefully before deploying 802.11-based voice.

Emergency Responder cannot track the location of wireless phones using the MSE. The only option is subnet-based tracking which implies that there must be a one-to-one relationship between subnets and Emergency Response Locations (ERLs). This also implies that mobility roaming groups must end at each ERL boundary. Since a WLC can only exist in a single mobility group, this means that there must be a WLC per ERL; or, to use H-REAP with local switching. In either scenario you must perform a hard roam at the boundary which would drop any call in progress, emergency or not. If device mobility is enabled in UC Manager, the subnet change would trigger a full phone reset.

This product limitation will affect customers even in  locations/states that do not fall wihin E911 laws:

A great example is when a customer has a group of buildings that are in close proximity to one another (i.e. a campus). By close I mean roughly 20 minute drive or less. If the controllers are in the same mobility group, the phone’s registration is cached for a period of time and the phone just performs a layer-three roam to its original controller. There are many customers who have campus environments or multiple locations in the same city.

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