[mythtv-users] Network Bridging my Ceton InfiniTV 4

Tom Bongiorno two.bits.11 at gmail.com
Mon Aug 8 23:35:32 UTC 2011

On Mon, Aug 8, 2011 at 3:25 PM, Ronald Frazier <ron at ronfrazier.net> wrote:
> On Mon, Aug 8, 2011 at 1:23 PM, Tom Bongiorno <two.bits.11 at gmail.com> wrote:
>> This sorta worked, but had some negative side effects.  Since I use IP
>> reservations on my router and the InfiniTV 4 MAC address changes upon every
>> reboot, the IP would jump all over.  Is there any way to get the InfiniTV 4
>> to retain a static MAC address?  There may be a couple more problems, but I
>> will have to look into it when I get home.
> I misread this the first time. I thought you were talking about the IP
> address changing, but you were talking about the MAC. Yeah, I know
> what you are talking about. Every time the Ceton reboots, it seems to
> have a different MAC address for the ctn0 interface. However, that
> doesn't matter because when you setup bridging, you don't actually
> assign ctn0 an IP. Let me give a little background info first.
> When you install and setup a ceton infinitv 4 card, it creates sort of
> a virtual LAN in your linux box (not a VLAN, that's a different
> concept...this is just a regular LAN that just doesn't physically
> exist). On this virtual LAN, there are 2 clients. The first client is
> your linux box, and it communicates on this LAN via the ctn0 network
> interface. The other client is resides on the ceton card itself. The
> ceton card itself runs a linux OS, so you can think of it as a
> computer on a card that you plug into the PCIe bus, rather than a
> traditional computer you plug into a network port on your
> router/switch.
> So now, on this virtual LAN, there are actually the two host...ctn0
> and the card itself. For configuration, ctn0 is configured just like
> any other ethernet card (using /etc/network/interfaces or whatever
> management tool your distribution uses), and the card is configured
> using it's web interface. You can set either (or both) clients to get
> their configuration from DHCP.
> Now, when you bridge 2 network interfaces (ctn0 and eth0) together,
> what you end up doing is assigning neither interface an IP address.
> Instead, it creates another virtual network interface called br0. You
> assign an IP address to only br0, and it handles routing all the
> packets between eth0, ctn0, and br0 as appropriate.
> Now, lets step back a minute to before you setup the bridge. You had
> had an eth0 with an IP of (for example), you had ctn0
> with an IP of (for example), and you had the ceton card
> itself (the client on the other end of that virtual LAN) with an IP
> address of
> When you install the bridge, you have it assign the br0 interface the
> IP (instead of assigning it to eth0). If you are using
> DHCP to do this assignment, you probably don't have to do anything
> because (if it works like it did for me) it just cloned the MAC
> address from eth0 to br0, so br0 automatically got the same IP. As I
> said, ctn0 and eth0 don't get an IP address. The bridge will handle
> all of the magic of forwarding packets to each interface as
> appropriate.
> So now, the question is...what IP is your Ceton card? Well, if you
> didn't change it already, it's still going to be,
> however there is an issue here. By default, the 200.* and the 0.* IP
> ranges are 2 entirely different subnets. Normally you can work around
> this by telling each system to use a /16 mask instead of /24, making
> one big subnet of 192.168.*.*, but unfortunately in my experience, the
> ceton doesn't seem to handle this properly. Instead, you have to
> reassign the ceton card an IP on the 0.* subnet. If you setup the
> ceton (not the ctn0 interface, but rather setup the card using the web
> interface) to use DHCP, the bridge will forward the DHCP request from
> the card to your primary network, and then forward the DHCP response
> back to the card, and it will get an IP assigned by your DHCP server.
> Then, as usually, you can configure your router (or whatever serves
> your DHCP) to serve a fixed IP based on the MAC.
> So, to summarize the steps:
> 1) configure the ceton for DHCP, or configure it for a statuc IP
> address on the same subnet as the rest of your network. As soon as you
> do this, the card may instantly stop responding to all your requests
> (meaning the page won't even reload when you click submit). If that
> happens (it does if you set it to a static addres...I don't recall
> what it does if you use DHCP), the card will NOT be accessible via the
> web interface until you complete the rest of this process. So, make
> absolutely sure you know what address you set it to, and double/triple
> check that you didn't make a typo.
> 2) Enable bridging by configuring /etc/network interfaces. Set eth0
> and ctn0 as static, but do not actually assign them an IP address.
> Setup br0 to get configured by DHCP or with static settings.
> 3) Reboot, and now everything will be on the same subnet, your
> interfaces will be bridged, and you can access the ceton web interface
> by it's new IP address.
> FYI, here is my current /etc/network/interfaces
> auto lo
> iface lo inet loopback
> allow-hotplug eth0
> iface eth0 inet static
> allow-hotplug ctn0
> iface ctn0 inet static
> auto br0
> iface br0 inet static
>        address
>        netmask
>        network
>        broadcast
>        gateway
>        dns-nameservers
>        bridge_ports eth0 ctn0
>        bridge_fd 0
>        bridge_stp off
> --
> Ron Frazier
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> mythtv-users at mythtv.org
> http://www.mythtv.org/mailman/listinfo/mythtv-users


Thanks for the input.  I did know and understand just about everything
you said.  I guess I knew more than I thought.  From what I have read
and witnessed, the bridge takes on the lowest MAC address of all the
interfaces, and my eth0 is pretty high starting with f4.  The Ceton
MAC address is almost always lower than eth0.  Since the ctn0 is
random, then br0 is random.  It may not be possible to set an IP
reservation in my router.  I tried the bridge_hw option to set the br0
MAC to that of eth0, but I get a "SIOCSIFHWADDR: Operation not
supported" error.


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