[Dnsmasq-discuss] VLANs and multiple IP addresses for one mac address

[Simon Kelley]

On 24/06/14 10:08, David Joslin wrote:
> I have a wireless network split into several vlans, each with its own
> subnet, with dnsmasq serving all vlans. The wireless network is a Ubiquti
> Unifi system and the access points all have static IP addresses on the
> management vlan. Additionally, the access points each request IP addresses
> via DHCP for the other vlans and dnsmasq correctly allocates the IP
> addresses for the relevant vlans.
> 
> I noticed in dnsmasq's logs recently a bunch of 'lease not found' messages
> whenever the access points attempted to renew the leases for these
> addresses. The cause seems to be this: an access point's IP addresses are
> all used on the same interface on the access point so when it renews these
> addresses, the requests all come from the same mac address. Dnsmasq
> services these requests but only the last address allocated is stored in
> the lease file (I'm assuming the other addresses allocated are briefly
> stored but then overwritten by subsequent allocations). So the access
> points are happy enough - they have the addresses they need correctly
> allocated by dnsmasq - but dnsmasq's lease file only records the last
> address allocated. When the access points renew the leases, dnsmasq
> generates the 'lease not found' error because there's no record of the
> allocation in the lease file.
> 
> The error messages themselves are no big deal and the access points do get
> the correct addresses. The problem I can foresee is that dnsmasq might
> allocate addresses to other clients that it has already allocated to the
> access points because it has no record of those allocations in its lease
> file.
> 
> Is there any way dnsmasq can record more than 1 IP address against a mac
> address? Or is there any other way round this problem? The access points
> don't give any options for IP configuration apart from the address on the
> management vlan; there aren't any configuration options for these DHCP
> requested addresses.

The obvious way to fix this would be to have the access points supply a
different client-id for each VLAN. Client-ids trump MAC addresses as
unique identifiers for leases. The lack of configuration options would
seem to preclude that, however.

You could at least solve the worry about having access point addresses
re-allocated by giving them static addresses on each VLAN, associated
with the MAC address.

Cheers,


Simon.




> 
> Any help would be greatly appreciated.
> 
> David
> 
> 
> 
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