[Dnsmasq-discuss] Cannot override DHCP server-identifier (option 54) ?

Benjamin Picardat bpicardat at netinary.com
Tue Dec 2 16:18:15 GMT 2014


Hello,

Here is my situation: I have two or more dnsmasq on distinct servers that
are in "failover" mode thanks to keepalived
(http://www.keepalived.org/documentation.html). That means that there is ONE
virtual IP address that is attributed to the master server (another master
is elected if this one falls, and it will take that IP address). So the
interface on which dnsmasq distributes the addresses with DHCP will have two
IPs: the real one (let's say 192.168.0.11 for server 1, .12 for server 2.)
and a secondary address (192.168.0.10), the virtual IP. So 192.168.0.10 will
always be the IP of the DHCP server, whichever one may be the master.

That being said, what I would like to do is that dnsmasq sends the secondary
IP in option:server-identifier (option 54) instead of the primary one, so
that the client would always communicate with the current master.

 

I was able to do this for option:router (3), with the configuration line: 

dhcp-option=tag:eth2,3,192.168.0.10

With that I receive the correct value in the client when I do a request.

 

But with:

dhcp-option=tag:eth2,54,192.168.0.10

In the client I still receive the primary IP address 192.168.0.11 in the
option 54 of the offer.

 

Removing the tag has no effect.

 

Should I be able to override the server-identifier option ? If yes, what
could I be doing wrong ?

 

Tested with  dnsmasq 2.58 and 2.72.

 

Thanks for your help and time,

Ben

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