CUCM Device mobility device CSS change

[Paul Austin]

Hello, I have a cucm cluster version 12.X. All works fine except device mobility. The device when moved between sites is recognised as moved base on the IP address and the roaming parameters change EXCEPT the device CSS. I have seen conflicting things about different Device Mobility Groups assigned to the device pools and using the same one (all from Cisco employees) but neither work. I have also tried configuring the device in CUCM without any device CSS without success.

All the config has been defined as far as guides go that I can see.

What am I missing here?

Thanks All.

[Maren Mahoney]

The way Device Mobility works is:

If the Home device pool and the Roaming device pool are in the same device mobility group (DMG), then the device CSS is changed to the roaming Device CSS (and AAR CSS, etc.) as set on the Device Pool configuration page.

If the Home device pool and the Roaming device pool are in different device mobility groups, then the device CSS is not changed.

The reasoning being: If an SJ device is roaming to NYC and the person dials an NANP number (like Domino's Pizza) the PSTN in SJ and the PSTN in NYC would both 'understand' the number and know what to do. So configure the SJ and NYC device pools with the same DMG so the Device CSS can be changed when roaming, and the SJ device can use the NYC gateways (as set by Device CSS on the Device Pool configuration page) for PSTN calls.

But if an SJ device roams to London and dials that same number the PSTN in London would have no idea what to do with that number, so instead the call should be sent back over the WAN to SJ and placed out the SJ PSTN gateway so the number dialed is 'understood' by the PSTN. In that case the SJ and London device pool would be in different DMGs so the Device CSS is not changed when roaming.

Device Mobility PL and DMG Relationships

This relies, of course, on at least some of the route patterns involved using site-specific Route List/Route Group configurations rather than Local Route Group. LRG is one of the 'Roaming' parameters changed based on Physical Location (PL) rather than DMG.

If you are working with Globalized Call Routing (a.k.a.: Plus dialing or E164 dialing) then all sites are placed in the same DMG regardless of location because it will be the Outbound Transformation CSS for calling- and called-party that will localize numbers regardless of the source or dialing domain.

I hope this is helpful. I teach this (among other things!) for a living, so if you have questions I am happy to help clarify.

Maren

[Paul Austin]

Hi Maren, Thats great. Will give it a go. Would you normally leave the device CSS blank in the CUCM config so it would always load the roaming device CSS according to the roaming config?

Thanks

Paul

[Maren Mahoney]

A device will use the Device CSS as listed on the Phone configuration page during normal operations. If you want the Device CSS to change during roaming with Device Mobility, then a "Device Mobility Calling Search Space" needs to be configured on the roaming Device Pool (under the section: "Device Mobility Related Information"). The CSS listed there is the Device CSS that will be used by a device while roaming to a Device Pool in the same DMG.

If a phone is roaming to a device pool in the same DMG and no device pool is listed in this section of the roaming device pool configuration page, then the device will still pick up the setting from the roaming device pool which - because none is set - becomes the 'None' CSS.

Essentially, you always want both set (on the device and on the roaming device pool) to make things work properly. Does that answer the question you are asking?

Maren

[Paul Austin]

Hi Marem, Thanks for the info. Unfortunately, it didn't work as expected and the device CSS remained as per configured on CUCM rather than the roaming CSS. So a TAC case has been opened.

Thanks anyhow.

Paul

[Roger Kallberg]

Can you please share screenshots of both the home and the roaming device pools as well as the DMI configuration for both device pools?

[Roger Kallberg]

You would configure a CSS on the device. The reason is that when the device is on its home location it will not be identified as roaming and will therefore not get the roaming CSS, so if you don’t configure a CSS on the device it would not work when it is in the home location.

[TechLvr]

@Paul Austin I believe your device CSS won't visually change to your mobility CSS on the device configuration page but your calls should be using the mobility CSS while roaming. Have you tested your calls to verify that? 

[Roger Kallberg]

That is correct, the configuration on the device configuration page in CM would not be altered. To see the roaming settings used you’d have to look at the mobility status on the device configuration page.

[Paul Austin]

Hi All, Thanks for the excellent suggestions. I have managed to get it working as designed. I was good with the configuration after all. There is a bug in CUCM where it doesn't like a "Device Mobility Group" IP range that has a 19 bit subnet mask. It works great with a 20, 24 and 32 bit mask just not a 19 bit mask. So we will have to enter two 20 bit subnets. It's not a problem just darn confusing. Left with TAC to deal with.

[Maren Mahoney]

The issue was a /19 mask? How very interesting! I'm going to test this in my lab asking the question, "Is it all odd-length masks (/19 /23 etc.) or just a /19. Thanks for sharing this!

Maren

[Roger Kallberg]

Interesting indeed. Did you happen to get a bugID on the defect from TAC? What specific version of CM do you use?

[Paul Austin]

Hi All, Sorry no bug ID yet - perhaps a new one? I'll post it as soon as I get it. Version we have is 12.5 SU3.

Thanks for the assistance.