[Dnsmasq-discuss] Incorrect broadcast address given

OB Lutz ob.lutz at gmail.com
Wed Oct 8 17:03:18 BST 2008


192.168.8.2 is inside 192.168.8.0/27, just as 192.168.8.226 is inside
192.168.8.224/27

bmf0 is an interface created by the olsrd broadcast/multicast
forwarding plugin. he captures anything sent to multicast addresses.
I'm not sure what ip it requires to be on, if it has restrictions at
all. It may be possible to move him to a different address, but all
the available addresses are inside the router's subnet.

On Wed, Oct 8, 2008 at 11:45 AM, Simon Kelley <simon at thekelleys.org.uk> wrote:
> OB Lutz wrote:
>>
>> # ip addr show
>> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
>>    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>>    inet 127.0.0.1/8 brd 127.255.255.255 scope host lo
>> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
>> state UP qlen 100
>>    link/ether 00:d0:12:09:91:52 brd ff:ff:ff:ff:ff:ff
>> 3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast
>> state DOWN qlen 100
>>    link/ether 00:d0:12:19:91:52 brd ff:ff:ff:ff:ff:ff
>> 4: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
>> state UNKNOWN
>>    link/ether 00:d0:12:09:91:52 brd ff:ff:ff:ff:ff:ff
>>    inet 192.168.8.225/27 brd 192.168.8.255 scope global br-lan
>> 5: wifi0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
>> state UNKNOWN qlen 1000
>>    link/ieee802.11 00:15:6d:63:d4:31 brd ff:ff:ff:ff:ff:ff
>> 6: ath0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
>> state UP qlen 1000
>>    link/ether 00:15:6d:63:d4:31 brd ff:ff:ff:ff:ff:ff
>>    inet 192.168.8.226/32 brd 255.255.255.255 scope global ath0
>> 7: bmf0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc
>> pfifo_fast state UNKNOWN qlen 500
>>    link/[65534]
>>    inet 192.168.8.226/32 brd 192.168.8.226 scope global bmf0
>>
>>
>
> Looks like the duff broadcast address is being pulled from bmf0 because it
> has an address inside the range for br-lan
>
> srk at ermintrude:~$ ipcalc 192.168.8.225/27
> Address:   192.168.8.225        11000000.10101000.00001000.111 00001
> Netmask:   255.255.255.224 = 27 11111111.11111111.11111111.111 00000
> Wildcard:  0.0.0.31             00000000.00000000.00000000.000 11111
> Network:   192.168.8.224/27     11000000.10101000.00001000.111 00000
> HostMin:   192.168.8.225        11000000.10101000.00001000.111 00001
> HostMax:   192.168.8.254        11000000.10101000.00001000.111 11110
> Broadcast: 192.168.8.255        11000000.10101000.00001000.111 11111
> Hosts/Net: 30                    Class C, Private Internet
>
> That's why your second example works, since bmf0 is at 192.168.8.2.
>
>
> The code in dnsmasq has an implicit assumption that the ip-ranges for all
> the interfaces are disjoint. It's probably possible to tweak this code, but
> the best course of action may be to use a different address for bmf0, if
> that's possible.
>
>
> Cheers,
>
> Simon.
>
>
>



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