[Dnsmasq-discuss] 'shared-network' behavior would be huge

[Ryan Gray]

Update on testing the new shared-network configuration:  My lab
network is the happiest network right now. This is great.

A few clarifications: I needed to set the source part of the
shared-network parameter to the IP of my relay, not the IP or
interface of my dnsmasq server. My dnsmasq server is at 10.200.200.1
which is bound to its br0 interface. My dhcp relay (Brocade switch)
holds the gateways for VLANs that need DHCP. The one I'm testing is a
vlan with an IP interface of 192.168.127.254/24 and a subinterface
192.168.128.254/24, so all requests from that VLAN are coming from
192.168.127.254.

I added this to my config:

shared-network=192.168.127.254,192.168.128.0

And it works!  I am even successfully handing out some addresses based
on nothing other than their subscriber-id (whole different talk show),
and it's now working.

What if I know that an interface is going to have multiple 'gateway'
IPs, but I'm not sure which one the switch/router will be using as its
source. In the example above, if I don't know whether or not the
requests will be coming from .127.254 or .128.254, can I safely just
have a 'shared-network' config line for each even though one will be a
bit redundant (shared-network=192.168.127.254,192.168.127.0)?

So far, this is really great. Thank you so much.


Regards,
Ryan Gray

On Sun, Mar 31, 2019 at 5:13 PM Simon Kelley <simon at thekelleys.org.uk> wrote:
>
>
>
> On 30/03/2019 18:33, Ryan Gray wrote:
> > TLDR; How do I use "shared-network" exactly?  :)
> >
> > Everything compiled and is up and running with no changes to my
> > existing configs or method of execution. I'm a little unclear about
> > how to hold this tool.
> >
> > Assuming a router interface of 192.168.4.126/25 and no sub interfaces,
> > I typically do something like this:
> >
> > dhcp-range=set:"internet-192_168_4_0_25",192.168.4.1,192.168.4.125,255.255.255.128,1h
> > tag-if=set:internet-pool,tag:internet-192_168_4_0_25
> > dhcp-option=tag:"internet-192_168_4_0_25",3,192.168.4.126
> > dhcp-option=tag:"internet-192_168_4_0_25",1,255.255.255.128
> > dhcp-option=tag:"internet-192_168_4_0_25",5,8.8.8.8
> >
> > If I add another gateway IP to that router interface (I use "gateway
> > IP" loosely), 192.168.5.0/24 and  and assuming the router with the
> > ip-helper configured is, by default, going to say "hey, I'm
> > 192.168.4.126". With ISC, having ranges for 192.168.4.1-125 and
> > 192.168.5.1-253 within the block of config that defines a
> > shared-network would make things copacetic.
> >
> > The question:  In this scenario, am I to start dnsmasq with
> > "--shared-network=192.168.4.126,192.168.5.0"    ?   If so, I'm not
> > sure if my subnet definition strategy above is going to stay the same
> > because I'm not sure how dnsmasq is going to treat this in regards to
> > tags.  Perhaps I'm just looking at this sideways.
> >
>
>
> You need to have something like
>
> shared-network=192.168.4.1,192.168.5.0
>
> assuming that the interface on the machine running dnsmasq is 192.168.4.1
>
> or
>
> shared-network=eth0,192.168.5.0
>
> assuming that the interface is so-named.
>
> Either of these will allow dnsmasq to allocate addresses on the sunnet
> that includes 192.168.5.0, but to make that happen you need a dhcp-range
> which tells it which addresses are available. This dhcp-range MUST have
> the netmask: normally dnsmasq can figure out the netmask, but it doesn't
> have enough information in this case.
>
> You can set tag in the dhcp-range, as before, and use it to control the
> DHCP options sent to the client (which should include router, as the
> normal default route option won't be sent.
>
>
> Simon.
>
>
>
> > On Fri, Mar 29, 2019 at 4:13 PM Simon Kelley <simon at thekelleys.org.uk> wrote:
> >>
> >> On 29/03/2019 20:36, Ryan Gray wrote:
> >>> Hello other humans,
> >>>
> >>> First, Simon Kelly, thank you for dnsmasq.
> >>>
> >>> I noticed here
> >>> http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2018q4/012700.html
> >>> that there was discussion of the possibility of supporting behavior like
> >>> ISC's 'shared-network'. Did this go anywhere? I would absolutely use
> >>> this and would be happy to perform any testing that would help. I didn't
> >>> see other mentions of this so I thought I'd ask.
> >>>
> >>> Dead serious, this would be spectacular.
> >>>
> >>>
> >>
> >>
> >>
> >> Today (actually, yesterday) is your lucky day:
> >>
> >> http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=ae5b7e04a1025167f1b80840e61432a3cea9625c
> >>
> >> Do please test!
> >>
> >>
> >> Simon
> >>
> >>
> >>> Regards,
> >>> Ryan Gray
> >>>
> >>>
> >>> _______________________________________________
> >>> Dnsmasq-discuss mailing list
> >>> Dnsmasq-discuss at lists.thekelleys.org.uk
> >>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> >>>
> >>
> >>
> >> _______________________________________________
> >> Dnsmasq-discuss mailing list
> >> Dnsmasq-discuss at lists.thekelleys.org.uk
> >> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> >