Failure of dhcp server failover

[Eugene Grosbein]

03.05.2016 0:13, Simon Hobson пишет:

>> I have several UniFi wireless access points (AP) controlled by UniFi Controller software.
>> These access points act as transparent L2 bridges supporting several distinct WLANs and vlans
>> for their wireless clients plus extra management vlan. They have wired uplink connected
>> to L2 manageable switches that insert DHCP option 82 to all request from AP themselves and their clients.
>> Mentioned vlans are routed by Cisco routers acting as DHCP relays. These routers relay DHCP requests
>> to pair of ISC DHCP Servers. There is ordinary IP pool for wireless clients and it works just fine.
>>
>> UniFi access points theyselves obtain their IP addressess and additional DHCP vendor options from DHCP servers.
>> Each AP makes use of at least two IP addresses, one per vlan.
>
> I'm using UniFi APs and they only get one address - on the management VLAN. They certainly do not get any other addresses - I've just checked the leases file at work to confirm.
> This is the case both in the office (HP switch), and on a customer site (Cisco switches).

My UniFi APs run with UniFi Controller 3.2.10 and Captive Portal/HotSpot enabled.
They request IP within untagged management VLAN and another IP within WLAN-assigned tagged vlan.
The Captive Portal does not work if AP cannot obtain IP from the same IP subnet as its wifi clients use.

> Could it be that your VLANs are not properly configured, and so your DHCP server is seeing one DHCP request from the AP repeated across multiple virtual interfaces ?

These requests come with different option 82 inserted and distinct DHCP XID, so they are not repeated.

> As pointed out before, if everything is correctly configured then the DHCP server will automagically work out the right subnet based on either the interface for non-relayed packets, or the GIAddr for relayed packets.

I use "ip unnumbered" routed network interfaces so GIAddr is the same for all vlans.