[Dnsmasq-discuss] No DHCP leases handed on bridge interface
Albert ARIBAUD
albert.aribaud at free.fr
Fri Jul 15 14:58:57 BST 2016
Hi Seb,
Le Fri, 15 Jul 2016 10:28:33 +0000 (UTC)
Sébastien Delafond <seb at debian.org> a écrit:
> Hello,
>
> I have a server with a bridge containing only one interface (ideally
> it'll of course include more interfaces, but I've tried to eliminate
> as many factors as possible):
>
> $ brctl show
> bridge name bridge id STP enabled interfaces
> br.eth0-2 8000.1cb72c761568 no
> eth0.2 $ ip ad show br.eth0-2
> 15: br.eth0-2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> \ noqueue state UP group default qlen 1000
> link/ether 1c:b7:2c:76:15:68 brd ff:ff:ff:ff:ff:ff
> inet 192.168.1.1/16 brd 192.168.255.255 scope global br.eth0-2
> valid_lft forever preferred_lft forever
>
> The DHCP-relevant parts of dnsmasq.conf are:
>
> interface=*
> dhcp-authoritative
> dhcp-lease-max=5000
> dhcp-range=set:br.eth0-2,192.168.1.100,192.168.1.200,86400
> dhcp-option=tag:br.eth0-2,3,192.168.1.1 # gateway
> dhcp-option=tag:br.eth0-2,1,255.255.0.0 # netmask
> dhcp-option=tag:br.eth0-2,6,192.168.1.1 # dns
>
> My client, sitting on the other end of eth0.2, is issuing DHCP
> requests that correctly make it up to the server (tcpdump sees them
> on both eth0.2 and br.eth0-2). However, dnsmasq is acting like it
> doesn't receive them at all: it stays silent, even when run with "-d
> --log-dhcp". In strace, I don't see anything either after it's
> started.
>
> The most interesting point is probably that ISC-dhcpd serves DHCP
> leases just fine in the same exact setup: simply stopping dnsmasq and
> starting ISC-dhcpd with a minimal "subnet 192.168.0.0 netmask
> 255.255.0.0 { range 192.168.1.100 192.168.1.200;}" configuration
> results in leases being handed to the same client.
>
> Also, if I remove the bridge, assign 192.168.1.1/16 to eth0.2, and
> restart dnsmasq, then my client gets a DHCP lease.
>
> Another thing I've done is to replay all the aforementioned tests
> with a wlan0 interface instead of the eth0.2, with the same results:
> ISC dhcpd works fine, dnsmasq doesn't serve DHCP over the bridge
> containing only wlan0, but does if I kill the bridge and work with
> wlan0 alone.
>
> Any clue what's going on ? This is a 4.4.3 kernel, and I've tried both
> 2.62 from Debian jessie, and 2.76 from stretch.
Just to make sure: "eth0.2" would normally denote a virtual interface
for VLAN 2 traffic on eth0. Are VLANs involved in your network setup?
> Cheers,
>
> --Seb
Amicalement,
--
Albert.
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