Hello.
Quick reader version:
Create an interface pair with vEth, add one of the pair's interfaces to the
bridge the AP's should be connected to, set up hostapd's dynamic VLAN
tagging feature as described in the example configuration file with the
other interface of the pair as the interface where tagged frames should
appear and comment 'bridge=' from the wifi interface's configuration
options. Restart hostapd.
Long version:
I'm running a quite peculiar setup of my main server at home and that made
some special setups necessary. First an overview of my setup:
_____________ ________________________________________
| Core Switch | | Server ________________ |
| |------------------|eth0\ | KVM-router | |
| LAG 1| (un)tagged VLANs | bond0-br0-tap0--|eth0 | |
| |------------------|eth1/ | |________________| |
|_____________| | WIFI/ |
|________________________________________|
(I sincerely hope someone can make sense of this graphic...)
The problem about this setup is the KVM-based router above: It has one
interface (among others removed for understandability) which transmits and
receives frames for all known VLANs. Thus the bridge br0 has to maintain
those 802.1Q tags on all frames passing through it. Services running on the
server itself are thus bound to br0.<vlan-id> as needed.
Transferring frames from one VLAN to another is only done within the KVM-
based router, nowhere else.
Now with hostapd this posed a problem:
The default setup with nl80211 driver is to specify the bridge to which the
AP's interface should be added. All frames passing through the AP appear on
that very bridge.
In my setup this doesn't work anymore, as untagged frames would always be
part of VLAN 1, the last one where wifi-clients are supposed to appear not
to mention this renders VLAN-ID assignment by radius useless.
The solution to this problem (thanks to Paul Fertser for pointing me in that
direction) was to disable the general bridging in hostapd and putting a pair
of ethernet interfaces to perform communication with the bridge.
The setup now looks like this:
_____________ ________________________________________
| Core Switch | | Server ________________ |
| |------------------|eth0\ | KVM-router | |
| LAG 1| (un)tagged VLANs | bond0-br0-tap0--|eth0 | |
| |------------------|eth1/ | |________________| |
|_____________| | veth0/ |
| | |
| WIFI--veth1 |
|________________________________________|
In other words: A pair of virtual ethernet interfaces is created
(CONFIG_VETH and iproute2 is needed here) of which one is then added to the
bridge the AP is supposed to be connected to.
The other interface of the pair is specified as vlan_tagged_interface.
The changes in hostapd configuration look like this now:
> #bridge=br0 # Commented in favor of using vlan_tagged_interface
> dynamic_vlan=2
> vlan_file=/etc/hostapd/hostapd.vlan
> vlan_tagged_interface=veth1
This setup works well, including IPv4 DHCP and IPv6 autoconfiguration.
I hope this helps anyone running into a similar problem with hostapd.
Kind regards,
Marquel
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