Wireless Mobility and DHCP_REQ Help

[Adrian Jones]

Hi All,

I'm hoping someone can help with an issue we currently have. Possibly with mobility in our Wireless system. We are running WLC5508's in two seperate locations, if one fails all APs associated to it should fail over to the alternate. Software version is 7.6.110.0.

The issue we are seeing is some clients get no IP and the Client details in the WLC show a DHCP_REQ state when a client moves from one area or another (so migrating across APs) or in some cases, their connection drops when they seem to sit between AP's in a room. DHCP is via an external server.

Questions I have (apologies if they seem stupid):

1. Can we over-saturate an area with AP's. This has been suggested - we are talking small numbers such as 3 in one room, about 10 meters apart. The number of client connections requires this.

2. Is there any special setting required to enable mobility on the WLC 5508? I can see some settings but not sure if there are specific non-default changes we should make. To me it looks like mobility is not working or as smooth as it should be.

3. When I look at a client, there is the PMIP Porperties with Mobility type as simple. What does simple mean? Is it an incorrect setting.

4. In the WLAN>advanced we have DHCP Address Assignment Ticked. Should the session timeout be set to the same lease time as the DHCP lease on the DHCP server?

5. Is there a way to limit the number of permit clients per AP - I think I found this but not sure.

6. In Controller>Mobility Management >Mobility Groups we have both WLCs listed. Should this be the case if the controllers are miles apart and clients cannot physically migrate between AP's presented on different controllers.

7. Is there a way we can force connections to a specific 2.4Ghz or 5Ghz band if the alternate looks saturated on an AP?

We have 2 profiles and this only occurs on one. The working one has Web-Auth for security policy and the one with issue is WPA2 and Auth 802.1x and CCKM. The issue has probably been present for a while but not reported until recently. System has been up for around 1.5 years.

Any help appreciated, there will be other questions when I get my head focused on them.

Regards

Adrian

[Rasika Nayanajith]

In general, if you have APs in same geographical area register to two different WLCs, that design has to change. All close by APs (that you expect clients to roam around) should go to same WLC for better performance.

Here is my responses to your other queries.

1. Can we over-saturate an area with AP's. This has been suggested - we are talking small numbers such as 3 in one room, about 10 meters apart. The number of client connections requires this.

You can. But it is not a good idea to put more APs without proper RF planning. More you put can interfere with each other if they operate in same channel.

2. Is there any special setting required to enable mobility on the WLC 5508? I can see some settings but not sure if there are specific non-default changes we should make. To me it looks like mobility is not working or as smooth as it should be.

Simply if you go to WLC CLI & issue "show mobility summary" command that output should verify the mobility peering. See below

http://mrncciew.com/2013/03/16/configuring-mobility-on-wlc/

3. When I look at a client, there is the PMIP Porperties with Mobility type as simple. What does simple mean? Is it an incorrect setting.

I do not see this is an issue. simply PMIP is for IPv6 clients & you can ignore this.

4. In the WLAN>advanced we have DHCP Address Assignment Ticked. Should the session timeout be set to the same lease time as the DHCP lease on the DHCP server?

5. Is there a way to limit the number of permit clients per AP - I think I found this but not sure.

Yes, you can. But it is a not good practice to set it.

6. In Controller>Mobility Management >Mobility Groups we have both WLCs listed. Should this be the case if the controllers are miles apart and clients cannot physically migrate between AP's presented on different controllers.

Typically you add WLCs into mobility list if you want smooth roaming between APs managed by these controllers. If you have APs in geographically apart (that roaming is not expected) then I would not configure both WLCs in same mobility group. Instead two WLCs will have two mobility group names.

7. Is there a way we can force connections to a specific 2.4Ghz or 5Ghz band if the alternate looks saturated on an AP?

Typically AP radio can handle ~200 clients (I am not suggesting you should have that many though). Do you see such higher numbers from your APs? "Bandselect" is the WLAN advanced setting that you can use to prefer dual band clients to 5GHz over 2.4GHz.

HTH

Rasika

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