[Dnsmasq-discuss] DHCP Relay, assign address from other vlan, with no dhcp listening on it

Shantanu Gadgil shantanugadgil at yahoo.com
Mon Sep 12 08:41:11 BST 2011


Hi,

dhcp-relay is very much possible with dnsmasq. the keyword is "dhcp proxy"
Also, when you setup the ranges, I think you are supposed to use the keyword 'proxy'.
I don;t think thats quite well documented in the example conf file.
I remember having seen it in the man page though.

Regards,
Shantanu

*** P.S. My memory about this is a bit sketchy as I had tried the same but found out that the routers in my grid do not have relay forwarding enabled and I set things up using many "satellite" DHCP servers! :) :)


--- On Mon, 9/12/11, SpiderX <spiderx at spiderx.dp.ua> wrote:

> From: SpiderX <spiderx at spiderx.dp.ua>
> Subject: Re: [Dnsmasq-discuss] DHCP Relay, assign address from other vlan, with no dhcp listening on it
> To: "dnsmasq-list" <dnsmasq-discuss at lists.thekelleys.org.uk>
> Date: Monday, September 12, 2011, 12:47 PM
> Thanks for reply.
> I have just tried this.
> conflg:
> #dhcp-range=tag:vlan-2-port-16,10.1.2.2,10.1.2.245,255.255.255.0,10.1.2.255,10m
> #dhcp-range=tag:#vlan-2-port-16,172.16.33.2,172.16.33.249,255.255.255.0,10m
> dhcp-host=48:5b:39:36:a2:73,10.1.2.100
> 
> Absolutely nothing happened with such config, dnsmasq did
> nothing.
> I saw DHCPDISCOVER in vlan1033 at the same time.
> When I commented out
> 'dhcp-range=tag:#vlan-2-port-16,172.16.33.2....',
> dnsmasq tried assign address from
> range 172.16.33.2-172.16.33.249.
> log:
> Sep 12 13:00:45 dnsmasq-dhcp[11194]: 2517313542 available
> DHCP range:
> 172.16.33.2 -- 172.16.33.249
> Sep 12 13:00:45 dnsmasq-dhcp[11194]: 2517313542 client
> provides name: laptop
> Sep 12 13:00:45 dnsmasq-dhcp[11194]: 2517313542
> DHCPDISCOVER(vlan1033)
> 172.16.33.121 48:5b:39:36:a2:73 no address available
> Sep 12 13:00:48 dnsmasq-dhcp[11194]: 2517313542 available
> DHCP range:
> 172.16.33.2 -- 172.16.33.249
> Sep 12 13:00:48 dnsmasq-dhcp[11194]: 2517313542 client
> provides name: laptop
> Sep 12 13:00:48 dnsmasq-dhcp[11194]: 2517313542
> DHCPDISCOVER(vlan1033)
> 172.16.33.121 48:5b:39:36:a2:73 no address available
> 
> With such results I assume that dhcp relay with dnsmasq
> don't work at all.
> Any ideas?
> 
> On Sat, Sep 10, 2011 at 11:09 PM, Shantanu Gadgil
> <shantanugadgil at yahoo.com>
> wrote:
> >
> > Hi Vladimir,
> > I assume you have tried with a simpler setup:
> > *without tags in the range part*.
> > Use the 'static' dhcp range method to assign the IPs
> based on mac address.
> >
> > Regards,
> > Shantanu
> >
> > --- On Sat, 9/10/11, SpiderX <spiderx at spiderx.dp.ua>
> wrote:
> >
> > > From: SpiderX <spiderx at spiderx.dp.ua>
> > > Subject: [Dnsmasq-discuss] DHCP Relay, assign
> address from other vlan, with no dhcp listening on it
> > > To: dnsmasq-discuss at lists.thekelleys.org.uk
> > > Date: Saturday, September 10, 2011, 2:58 PM
> > > Hello, my name is Vladimir.
> > > I'm trying to setup dnsmasq to work in DHCP Relay
> (RFC3046)
> > > environment.
> > > Compiled with tftp, dhcp support and without
> dbus, ipv6,
> > > idn.
> > >
> > > topology:
> > > client (dhcp,10.1.2.0/24) — l2 switch
> (172.16.33.50) —
> > > server with
> > > dnsmasq (172.16.30.252)
> > >
> > > server:
> > > ip a:
> > > 5: vlan0002 at eth1:
> <BROADCAST,MULTICAST,UP,LOWER_UP>
> > > mtu 1500 qdisc
> > > noqueue state UP
> > >     link/ether 00:1e:67:02:ad:6a brd
> > > ff:ff:ff:ff:ff:ff
> > >     inet 10.1.2.250/24 brd 10.1.2.255 scope
> > > global vlan0002
> > > 6: vlan0003 at eth1:
> <BROADCAST,MULTICAST,UP,LOWER_UP>
> > > mtu 1500 qdisc
> > > noqueue state UP
> > >     link/ether 00:1e:67:02:ad:6a brd
> > > ff:ff:ff:ff:ff:ff
> > >     inet 10.1.3.250/24 brd 10.1.3.255 scope
> > > global vlan0003
> > > ..........lots of vlan......
> > > 88: vlan1033 at eth1:
> <BROADCAST,MULTICAST,UP,LOWER_UP>
> > > mtu 1500 qdisc
> > > noqueue state UP
> > >     link/ether 00:1e:67:02:ad:6a brd
> > > ff:ff:ff:ff:ff:ff
> > >     inet 172.16.33.252/24 scope global
> vlan1033
> > > sysctl:
> > > net.ipv4.ip_forward=1
> > >
> > > config:
> > >
> dhcp-circuitid=set:vlan-2-port-16,00:04:00:02:00:10
> > > dhcp-option=option:router,10.1.2.250
> > >
> dhcp-range=tag:vlan-2-port-16,10.1.2.2,10.1.2.245,255.255.255.0,10.1.2.255,10m
> > >
> dhcp-range=tag:#vlan-2-port-16,172.16.33.2,172.16.33.249,255.255.255.0,10m
> > > dhcp-leasefile=/var/lib/misc/dnsmasq.leases
> > > dhcp-authoritative
> > > log-dhcp
> > > log-facility=/var/log/dnsmasq.log
> > >
> > > log:
> > > Sep 10 14:37:28 dnsmasq[20380]: started, version
> 2.58
> > > cachesize 150
> > > Sep 10 14:37:28 dnsmasq[20380]: compile time
> options:
> > > no-IPv6
> > > GNU-getopt no-DBus i18n DHCP TFTP no-conntrack
> IDN
> > > Sep 10 14:37:28 dnsmasq-dhcp[20380]: DHCP, IP
> range
> > > 172.16.33.2 --
> > > 172.16.33.249, lease time 10m
> > > Sep 10 14:37:28 dnsmasq-dhcp[20380]: DHCP, IP
> range
> > > 10.1.2.2 --
> > > 10.1.2.245, lease time 10m
> > > Sep 10 14:37:28 dnsmasq[20380]: reading
> /etc/resolv.conf
> > > Sep 10 14:37:28 dnsmasq[20380]: using nameserver
> > > 91.193.69.4#53
> > > Sep 10 14:37:28 dnsmasq[20380]: bad address at
> /etc/hosts
> > > line 2
> > > Sep 10 14:37:28 dnsmasq[20380]: read /etc/hosts -
> 1
> > > addresses
> > > Sep 10 14:37:39 dnsmasq-dhcp[20380]: 3769651775
> available
> > > DHCP range:
> > > 172.16.33.2 -- 172.16.33.249
> > > Sep 10 14:37:39 dnsmasq-dhcp[20380]: 3769651775
> client
> > > provides name: laptop
> > > Sep 10 14:37:39 dnsmasq-dhcp[20380]: 3769651775
> > > DHCPDISCOVER(vlan1033)
> > > 172.16.33.121 48:5b:39:36:a2:73 no address
> available
> > > Sep 10 14:37:44 dnsmasq-dhcp[20380]: 3769651775
> available
> > > DHCP range:
> > > 172.16.33.2 -- 172.16.33.249
> > > Sep 10 14:37:44 dnsmasq-dhcp[20380]: 3769651775
> client
> > > provides name: laptop
> > > Sep 10 14:37:44 dnsmasq-dhcp[20380]: 3769651775
> > > DHCPDISCOVER(vlan1033)
> > > 172.16.33.121 48:5b:39:36:a2:73 no address
> available
> > >
> > > So, dnsmasq got a DHCPDISCOVER message in
> vlan1033 with
> > > option82 that
> > > match tag vlan-2-port-16.
> > > Client doesn't get a lease because of
> 'tag:#vlan-2-port-16'
> > > in last
> > > dhcp-range, that's why I assume that tag
> vlan-2-port-16 is
> > > matched.
> > > The problem is dnsmasq completely ignore first
> range
> > > 'tag:vlan-2-port-16,10.1.2.2....', and always try
> to assign
> > > address
> > > from range 172.16.33.0/24.
> > > I think that happends because there is not ip
> address from
> > > network
> > > 10.1.2.0/24 on vlan1033 unlike ip address
> 172.16.33.252.
> > > So, I assume that dnsmasq assigns address from
> ranges that
> > > match ip
> > > addresses on interfaces dhcp packets come from.
> > > How dhcp relay supposed to work with such
> dnsmasq
> > > behavior?
> > >
> > > _______________________________________________
> > > 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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