[Dnsmasq-discuss] Use dnsmasq to assign static /32 addresses via DHCP

Peter Lieven pl at kamp.de
Tue Mar 12 11:56:22 GMT 2019


Hi,

we run several thousand virtual gateways which are used to assign /32 allocations to Virtual Servers via DHCP.


This so far runs pretty well except for one hack that we had to make and that I would like to avoid.

We assign the /32 networks out of /24 blocks that we reserved for this purpose. However, dnsmasq only
assigns IP addresses via an interface if the network is configured on that interface. We had to add some
more specific routes on the gateways to make a 2 hosts that receive a /32 out of the same /24 see each
other if they are on different gateways. In fact I would like to configure only one common virtual address
on the vserver facing interface lets say 10.255.255.255/32.

What I would like to need is an option to either make dnsmasq assign addresses out of an dhcp-range even
if the network is not configured on the dhcp interface or an option where dnsmasq runs in a mode where it

does not require dhcp-range options, but only works using dhcp-host entries and replies if gets a request

for a static mac address entry.


My config looks basically like this:

[virtual gw1]

dhcp-range=set:virtualgw,10.0.0.2,10.0.0.254,infinite,static

dhcp-host=52:54:00:00:00:01,10.0.0.2,vserver1

dhcp-option=tag:virtualgw,1,255.255.255.255
dhcp-option=tag:virtualgw,3,10.255.255.255
dhcp-option=tag:virtualgw,28,255.255.255.255

dhcp-option=tag:virtualgw,121,10.255.255.255/32,0.0.0.0,0.0.0.0/0,10.255.255.255


[virtual gw2]

dhcp-range=set:virtualgw,10.0.0.2,10.0.0.254,infinite,static

dhcp-host=52:54:00:00:00:02,10.0.0.3,vserver1

dhcp-option=tag:virtualgw,1,255.255.255.255
dhcp-option=tag:virtualgw,3,10.255.255.255
dhcp-option=tag:virtualgw,28,255.255.255.255

dhcp-option=tag:virtualgw,121,10.255.255.255/32,0.0.0.0,0.0.0.0/0,10.255.255.255


To make dnsmasq deliver addresses out of 10.0.0.0/24 I have to configure 10.0.0.1/24

on the DHCP interface. To ensure reachability between 10.0.0.2 and 10.0.0.3 I have

configured static routes 10.0.0.0/25 and 10.0.0.128/25 towards the default gw.

The configuration of 10.0.0.1/24 on the DHCP interface and the static routes is what I would like to avoid.


Thanks for your feedback,

Peter






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