If a system has more than one NIC then what happens by default regarding connecting to thre resto f the local network.
Does it simply choose the first NIC that 'appears' during boot to be the one that is used for 'itself'?
I realise that one can have multiple NICs and different routes etc. but I want to know what happens if (as I have at the moment) you have a system with three NICs (one real card and two on board ones). I have nothing clever configured, I just told the installation what the system's IP address was, what the default route was and what the DNS server was.
On Fri, 13 Oct 2006, cl@isbd.net wrote:
If a system has more than one NIC then what happens by default regarding connecting to thre resto f the local network.
Does it simply choose the first NIC that 'appears' during boot to be the one that is used for 'itself'?
This almost certainly varies from distro to distro. On FC4, the default route is, by default, the last interface to be brought up. The order in which the interfaces are brought up is determined by a line in /etc/init.d/network that says
LANG=C sort -k 1,1 -k 2n | \
which (I think) sorts them into alphabetical order of the interface type (e.g. eth, ppp, usb) then into numerical order of their number (e.g. eth0, eth1, ppp0, ppp1, usb0, usb1.)
On 14-Oct-06 Dan Hatton wrote:
On Fri, 13 Oct 2006, cl@isbd.net wrote:
If a system has more than one NIC then what happens by default regarding connecting to thre resto f the local network.
Does it simply choose the first NIC that 'appears' during boot to be the one that is used for 'itself'?
This almost certainly varies from distro to distro. On FC4, the default route is, by default, the last interface to be brought up. The order in which the interfaces are brought up is determined by a line in /etc/init.d/network that says
LANG=C sort -k 1,1 -k 2n | \
which (I think) sorts them into alphabetical order of the interface type (e.g. eth, ppp, usb) then into numerical order of their number (e.g. eth0, eth1, ppp0, ppp1, usb0, usb1.)
What I've never sussed out (on the one machine where I have two physical Ethernet cards) is how the OS (SuSE 7.2 in this case) decides which one is going to be eth0 and which eth1.
In my case, there was initially only one, so that was eth0 anyway. Then I installed the second one, and this is a different model from the first (first is 3Com 3c509, second a 3c590), so this may be the hook. But what would happen if (say) they were both 3x590? It may be that it depends on the order in which they are detected on bootup which would have to do with their PCI identities, but there I'm only guessing!
Best wishes to all, Ted.
-------------------------------------------------------------------- E-Mail: (Ted Harding) Ted.Harding@nessie.mcc.ac.uk Fax-to-email: +44 (0)870 094 0861 Date: 14-Oct-06 Time: 22:45:52 ------------------------------ XFMail ------------------------------
On Sat, 2006-10-14 at 22:45 +0100, Ted.Harding@nessie.mcc.ac.uk wrote:
In my case, there was initially only one, so that was eth0 anyway. Then I installed the second one, and this is a different model from the first (first is 3Com 3c509, second a 3c590), so this may be the hook. But what would happen if (say) they were both 3x590? It may be that it depends on the order in which they are detected on bootup which would have to do with their PCI identities, but there I'm only guessing!
I think that everything else being equal, lowest PCI bus ID wins
Actually I used to have a problem with my old Fujitsu sub notebook because depending on the link status of the ethernet socket at boot it would swap the wired and wireless interfaces.
However I think that was a special case.
On Sun, October 15, 2006 12:14 am, Wayne Stallwood wrote:
On Sat, 2006-10-14 at 22:45 +0100, Ted.Harding@nessie.mcc.ac.uk wrote:
In my case, there was initially only one, so that was eth0 anyway. Then I installed the second one, and this is a different model from the first (first is 3Com 3c509, second a 3c590), so this may be the hook. But what would happen if (say) they were both 3x590? It may be that it depends on the order in which they are detected on bootup which would have to do with their PCI identities, but there I'm only guessing!
I think that everything else being equal, lowest PCI bus ID wins
Actually I used to have a problem with my old Fujitsu sub notebook because depending on the link status of the ethernet socket at boot it would swap the wired and wireless interfaces.
However I think that was a special case.
We have servers from rackservers.com that break this rule, for some unknown reason eth0 and eth1 are switched. We have to modify kickstart rules only for these builds, which use almost identical hardware to others that we have.
Not very helpful, and no answer to the original question, but hey! :)
-Mark
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cl＠isbd.net -
Dan Hatton -
Mark Ridley -
Ted.Harding＠nessie.mcc.ac.uk -
Wayne Stallwood