What is AP H-REAP Native Vlan used for?

[PAUL TRIVINO]

We have a few APs - CAP3502 and LAP1242s for the most part - whose H-REAP "Native Vlan" doesn't match the switchport's native vlan.  It appears that the switchport native vlan is what gets used for the AP for DHCP (it gets an AP IP address from that network).  If so, does anyone know what the purpose of specifying the native vlan on the H-REAP config is?  I can think of no useful purpose, but if there is one I'd appreciate anyone who could say.

Thanks.

BTW this is on a 5508 controller running 7.0.240.0 code.

[Scott Fella]

The native vlan is required when you have multiple vlan's. The AP's vlan must be the native and all other vlan's are tagged. If you don't specify the native vlan in the h-reap tab, the AP and all local switched WLAN's will be placed in the native vlan or the access port if the port is in access mode. Even with the older Cisco autonomous AP's, the AP's vlan is always defined as the native vlan.

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[PAUL TRIVINO]

Thanks Scott - further info:  the Vlan Mappings are filled in with the appropriate Vlans, which are separate from the AP native vlan.  In this case vlans 202, 203, 204 and 206 are assigned to various SSIDs and the Native Vlan for the AP is set to 201.  The switchport is set to trunk all vlans and has native vlan 221, and it is from vlan 221 that the AP get's its own IP.

So on the one hand, if specifying the 'native' vlan were to avoid cases where the wrong vlan was native on the switch (and so, to tell the AP which vlan to use for itself and control traffic), I would expect the AP to have a vlan201 address.

If on the other hand this is merely a 'documentary' setting to say what the 'native vlan' *should* be, then I would expect the AP to have a vlan221 IP, which it does.

Just trying to find out if this setting does anything more than document.

[Scott Fella]

When you set the AP's native vlan, all it knows is that it will be on a vlan that is untagged. So you can set the port as an access port vlan 200 with native 201 on the AP and since the untagged packet (vlan 200) will be received on the AP, the AP will get dhcp from vlan 200. If you had a static address and the AP was setup for native vlan 201 and your trunk port was set for native vlan 206, then you would loose connectivity to the AP until you fixed the native vlan in the trunk.

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[PAUL TRIVINO]

- kind of my point, Scott.  As you say the AP will get an IP from DHCP, on whatever vlan is native on the switch port, regardless of the 'Native Vlan' setting in the AP config.  If the AP has a static IP, unless the switch port's native vlan matches that IP, you lose connection to the AP.

So unless I'm simply not understanding your answer, I am left still thinking that if the native vlan on the switch controls connectivity to the AP itself, no matter what value you put in the 'Native Vlan' field, then the field in the config does not really 'DO' anything.

Thanks!

[Scott Fella · Accepted solution]

Yes that is true. It's like if you had two switches with different native vlan's configured on the trunk. I see what your saying, but since I use static address a lot, it makes a difference in my installs. The AP only assumes its on the untagged vlan.

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[PAUL TRIVINO]

Thanks for taking the time, Scott.  We use DHCP with reservations, so if the port gets changed we can still at least FIND the AP, and we can move them from site to site.

[Scott Fella]

Yeah that would work. It's nice to keep it consistent, because others will get confused if you know what I mean:)

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[PAUL TRIVINO]

Do I ever!!!