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

Ryan Gray ryantgray at gmail.com
Mon Apr 1 18:35:19 BST 2019


On Mon, Apr 1, 2019 at 11:55 AM Simon Kelley <simon at thekelleys.org.uk> wrote:
>
> On 01/04/2019 16:33, Ryan Gray wrote:
> > 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.
>
> That's expected (and documented) if you're running a relay. In this
> case, the only information about which physical network the client is on
> is the relay address inserted into the DHCP request by the relay.

Totally makes sense.

Thank you for all of your work on this. Seriously, this addition is
greatly appreciated.


> > 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)?
>
> Yes, that should work fine.
>
>
> Cheers,
>
> Simon.
>
> >
> > 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
> >>>
> >
>



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