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

[Simon Kelley]

Is this a use for something like the ISC dhcpd shared-network configuration.


In the dnsmasq case, we could have something like

shared-network=<interface>,<address/prefix-length>

or

shared-network=<interface-address>,<address/prefix-length>

In the first case dnsmasq would behave _as_if_ the specified interface
carried the address and netmask specified.

In the second case, it would behave as if the interface which carries
interface-address also carried the address and netmask specified.

If I've understood correctly, you'd just need a shared-network
declaration for each of your /24s.



For the avoidance of doubt, this is NOT currently implemented on
dnsmasq, but it has been on the "desirable" list in my head for some time.


Simon.



On 12/03/2019 11:56, Peter Lieven wrote:
> 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
> 
> 
> 
> 
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>