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

Shantanu Gadgil shantanugadgil at yahoo.com
Sat Sep 10 21:09:10 BST 2011


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?
> 
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