can't make ipv4 dhcp and ipv6 static both exist

[Scott Sullivan]

On 10/30/2013 10:15 PM, James Knott wrote:
> A couple of things.  First off, my experience is with openSUSE, not
> Debian.  However, in my experience, bridges don't usually have IP
> addresses, as they work at level 2, not 3.

My experience is quite the opposite in regards to bridge interfaces. 
Most of the times I'm using a bridge it's because I want to be able to 
reach the OS by the same address regardless of what media it is on. 
Anyone using an OpenWRT device with wifi we see this as the br0 bridge 
interface will have the LAN and Wifi as member interfaces.

> Also, it's generally not
> necessary to use static IPv6 addresses.  The two common methods are MAC
> based and random number addresses.  It is possible to have both on one
> interface.  Of course, the other two options are static and DHCP.  I
> also see you're assigning a gateway address.  Again, that's generally
> not necessary with IPv6, as routers advertise themselves.

Again, just because the environment you've experienced take advantage of 
those features, you can't assume what is or is not necessary. Neil has 
not provided enough information to guess either way.

Neil, is it necessary for it to be static, or would one of the suggested 
auto-configuration methods be satisfactory?

> On my home network, I run a few computers, along with a smart phone and
> tablet and I've never had to configure an IPv6 address or router on any
> of them.  It just works automagically.  I get my IPv6 subnet from a
> tunnel broker and other than the firewall, I didn't have to do any
> address configuration at all.  The router learned my subnet from the
> tunnel and all the devices addresses are MAC based or random and all
> just work.  This is one of the (many) benefits of IPv6.

Neil, I'd love to know which broker you using. Maybe you could let us 
know your experience and break it out in to a separate thread for others 
to chime in on?

> BTW, I have a /56 subnet, which is 2^72 addresses, or about a trillion
> times the entire IPv4 address space.

My God... it's full of IPs...

> Neil Watson wrote:
>> Greetings,
>>
>> On a debian laptop I have the following interfaces file. For some
>> reason the
>> IPV6 address will not set. Why?

Neil, I would test if it is setting the IPv6 address at all. Comment out 
the IPv4 DHCP and make sure the IPv6 config is correct on it's own. I 
would then fire up dhclient against the interface and observe it is the 
fault of DHCP changing the address after the fact.

What I'm curious about is if it's a side effect issue. IPv6 gets set 
immediately as it's static, but then the DHCP takes longer waiting for 
the DHCP server, assigns it's address when it get it and clears the IPv6 
in the process.


>> auto lo br0
>> iface lo inet loopback
>> iface lo inet6 loopback
>>
>> allow-hotplug br0 wlan0
>>
>> iface br0 inet dhcp
>>          bridge_ports eth0
>>          bridge_stop off
>>          bridge_fd 0
>>          bridge_maxwait 0
>>
>> iface br0 inet6 static
>>          address 2001:470:1d:a2f::4
>>          netmask 64
>>          gateway 2001:470:1d:a2f::1
>>
>>
>> root at neptune:/etc/network# ifconfig
>> br0       Link encap:Ethernet  HWaddr f0:de:f1:d8:0d:87           inet
>> addr:172.16.100.19  Bcast:172.16.100.255  Mask:255.255.255.0
>>            inet6 addr: fe80::f2de:f1ff:fed8:d87/64 Scope:Link
>>            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>>            RX packets:1965 errors:0 dropped:0 overruns:0 frame:0
>>            TX packets:1647 errors:0 dropped:0 overruns:0 carrier:0
>>            collisions:0 txqueuelen:0
>>            RX bytes:1511472 (1.4 MiB)  TX bytes:217730 (212.6 KiB)
>>
>> eth0      Link encap:Ethernet  HWaddr f0:de:f1:d8:0d:87           UP
>> BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>>            RX packets:7437 errors:0 dropped:0 overruns:0 frame:0
>>            TX packets:4924 errors:0 dropped:0 overruns:0 carrier:0
>>            collisions:0 txqueuelen:1000
>>            RX bytes:7126724 (6.7 MiB)  TX bytes:650467 (635.2 KiB)
>>            Interrupt:20 Memory:f2500000-f2520000
>>
>> 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:10 errors:0 dropped:0 overruns:0 frame:0
>>            TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
>>            collisions:0 txqueuelen:0
>>            RX bytes:1380 (1.3 KiB)  TX bytes:1380 (1.3 KiB)
>>

-- 
Scott Sullivan

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