[Dnsmasq-discuss] dnsmasq not overriding leases for static assigments

Petr Menšík pemensik at redhat.com
Sat May 15 17:32:11 UTC 2021


Hi Jesus,

To my best knowledge, access-points are usually transparent from direct
end clients. They do not change hardware address of clients going to AP
or any machines behind it.

In my experience, hardware access points doing just AP transparent
bridge are not problematic. Directly connected devices usually do not
have any problems. Problematic are often often clients behind wireless
client doing "transparent" bridge, which cannot be completely
transparent. In my schematics, only client-eth3 would have hardware
address mangled, because client-bridge3 connects to AP with single HW
address, but can provide connectivity for more than single client.
Usually those clients are highly problematic.

 client-w1 ---------------------\
 client-w2 ---------------------[ AP ] ---- [ router ] ----- [AP2]
client-eth3 --- client-bridge3 -/

If your APs indeed transform mac addresses of directly connected
clients, replacing them with different kind of AP or configuration might
work. I would expect AP directly connected to router/switch by cable
should work without problems.

Problems should arise with client-bridge3 and similar. That includes
also any kind of "repeaters" covering blind spots, when connected by
wifi itself. Without special connection it would connect its own clients
using different hw address. Just because client cannot use multiple mac
addresses without some hacks. Those hacks are usually on link layer.

If you have multiple APs, I would recommend using just APs connected by
ethernet cable to common switch. Avoid "transparent" clients, they often
work only half way.

My opinions, which might be wrong.

Cheers,
Petr

On 5/15/21 1:38 PM, Jesus M Diaz wrote:
> Hello,
> 
> I have a 'TP-Link One-Mesh' system at home formed by the main router and
> three satellite access-points. It works really well making a good coverage
> over the house with smooth change from one AP to the other, but it has a
> caveat: for DHCP requests, the AP change the client mac-address with a
> combination of the three last duplas from the own AP mac-addr and the last
> three ones from the client itself.
> 
> So, imagine my client mac-addr is A:B:C:D:E:F and my APs mac-addr are
> aN:bN:cN:dN:eN:fN, with N a number to identify the AP.
> 
> If the client connects directly to the router, the dhcp request will come
> from A:B:C:D:E:F. But if it connects to one of the AP, the dhcp request
> will come from dN:eN:fN:D:E:F.
> 
> This is not a problem for dynamic assignments (well, sometimes is for the
> name link in the dns part, but not critical).
> 
> But when I have static leases the problems. I have defined dhcp-hosts
> entries with multiple mac-addr, something the documentations explain as:
> 
> *As a special case, in DHCPv4, it is possible to include more than one
>> hardware address.
>> eg: --dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2 This allows
>> an IP address to be associated with multiple hardware addresses, and gives
>> dnsmasq permission to abandon a DHCP lease to one of the hardware addresses
>> when another one asks for a lease.*
> 
> 
> But the reality is that when a second request comes, dnsmasq finds the IP
> is in used and assigns a new one from the global pool, instead of the
> static one.
> 
> I have tried the configuration either using wildcards (*:*:*:D:E:F, given
> the last part of the mac-addr remains unchanged), but also defining each
> one of the possible cases
> (d1:e1:f1:D:E:F,d2:e2:f2:D:E:F,d3:e3:f3:D:E:F,A:B:C:D:E:F). Same outcome in
> both cases.
> 
> Am I doing something wrong? Any idea how to fix this?
> 
> Thanks in advance.
> 
> 
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-- 
Petr Menšík

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