[Dnsmasq-discuss] No DHCP leases handed on bridge interface

Albert ARIBAUD albert.aribaud at free.fr
Fri Jul 15 17:48:10 BST 2016


Bonjour Seb,

Le Fri, 15 Jul 2016 15:48:55 +0000 (UTC)
Sébastien Delafond <seb at debian.org> a écrit:

> On 2016-07-15, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> > That leads to further questions, at least. VLANs do not cause
> > problems for dnsmasq, but bridging VLANs may be tricky and more
> > prone to network misconfigurations.
> >
> > So just to make sure, can you list all interfaces and all bridges in
> > your system, including ifconfig outputs?  
> 
> Sure:
> 
>   $ brctl show
>   bridge name     bridge id               STP enabled     interfaces
>   br.eth0-2               8000.1cb72c761568       no
> eth0.2 $ ifconfig
>   br.eth0-2 Link encap:Ethernet  HWaddr 1c:b7:2c:76:15:68  
> 	    inet addr:192.168.1.1  Bcast:192.168.255.255
> Mask:255.255.0.0 UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> 	    RX packets:872 errors:0 dropped:0 overruns:0 frame:0
> 	    TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
> 	    collisions:0 txqueuelen:1000 
> 	    RX bytes:130641 (127.5 KiB)  TX bytes:258 (258.0 B)
> 
>   eth0      Link encap:Ethernet  HWaddr 1c:b7:2c:76:15:68  
> 	    UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> 	    RX packets:140624 errors:0 dropped:0 overruns:0 frame:0
> 	    TX packets:103007 errors:0 dropped:0 overruns:0 carrier:0
> 	    collisions:0 txqueuelen:1000 
> 	    RX bytes:91383944 (87.1 MiB)  TX bytes:74433059 (70.9 MiB)
> 	    Interrupt:180 Base address:0x5000 
> 
>   eth0.1    Link encap:Ethernet  HWaddr 1c:b7:2c:76:15:68  
> 	    inet addr:172.16.25.234  Bcast:172.16.25.255
> Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> 	    RX packets:748 errors:0 dropped:0 overruns:0 frame:0
> 	    TX packets:355 errors:0 dropped:0 overruns:0 carrier:0
> 	    collisions:0 txqueuelen:1000 
> 	    RX bytes:51266 (50.0 KiB)  TX bytes:41482 (40.5 KiB)
> 
>   eth0.2    Link encap:Ethernet  HWaddr 1c:b7:2c:76:15:68  
> 	    UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> 	    RX packets:4 errors:0 dropped:0 overruns:0 frame:0
> 	    TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
> 	    collisions:0 txqueuelen:1000 
> 	    RX bytes:1312 (1.2 KiB)  TX bytes:258 (258.0 B)
> 
>   lo        Link encap:Local Loopback  
> 	    inet addr:127.0.0.1  Mask:255.0.0.0
> 	    inet6 addr: ::1/128 Scope:Host
> 	    UP LOOPBACK RUNNING  MTU:65536  Metric:1
> 	    RX packets:285419 errors:0 dropped:0 overruns:0 frame:0
> 	    TX packets:285419 errors:0 dropped:0 overruns:0 carrier:0
> 	    collisions:0 txqueuelen:0 
> 	    RX bytes:77987874 (74.3 MiB)  TX bytes:77987874 (74.3 MiB)
> 
> So, only one bridge (that's not bridging much right now since it only
> contains eth0.2).

... and no weirdness in the address/mask settings that I can see.

[...]

> Interesting issue, but it doesn't feel like what I'm facing right now:
> the fact that ISC dhcpd serves leases OK seems to indicate that the
> network configuration itself is all right.

OTOH, there *is* a link with the networking setup since dnsmasq works
without the bridge and stops working with the bridge. Also, the fact
tha ISC dhcp works might hinge on how ISC dhcp listens to requests
exactly vs. how dnsmasq does. What's the ISC dhcp config exactly?

> Plus, there really is not VLAN at all outside of that
> software-programmable NIC anyway: tcpdump -e confirms that packets
> going in and out (either on br0.eth-2 or eth0.2) are not tagged. I've
> tested that by assigning a manual IP to my client and initiating a
> telnet connection to the outside.
> 
> Does this make any sort of sense ? :)

Well, it certainly does not give me a definite clue as to what is wrong
with your dnsmasq.

Speaking of tcpdump, can you use it to capture a successful request to
ISC dhcp and a (failed) request to dnsmasq, on eth0.2 as well as on 
br.eth0-2, and make the captures files available somewhere?

> Cheers,
> 
> --Seb

Amicalement,
-- 
Albert.



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