10.7 Dealing with inconsistent naming of interfaces by the kernel
The names eth0, eth1, etc. are assigned by the
kernel in the order that the kernel creates the interfaces that go by those
names. While adapters that are detected at boot time are usually detected in
the same order every time, and are therefore assigned the same names every
time, the same is not true of adapters that are hot plugged. These can be
detected in any order and end up getting assigned different names by the kernel
on different occasions.
Because of this fact, on a system into which network adapters are hot plugged
it won't always do to define logical interfaces in
/etc/network/interfaces with names eth0,
eth1, etc., and to rely on the default mapping. Instead you must
give distinct names to the logical interfaces and use one of the following two
methods to restrict which logical interfaces can be assigned to which adapters.
One method is to use either the nameif utility (in the
net-tools package) or the more flexible ifrename
utility (in the ifrename package) to make the kernel assign names
to interfaces according to properties of the underlying adapters. With this
naming scheme in effect, the physical interface name can be used to infer which
adapter underlies it.
Another method is to use ifup's mapping mechanism in such a way
that a logical interface is chosen for a physical interface being brought up
according to some property of the adapter that underlies it.
Suppose, for example, you have two different network adapters which you use
with networks net1 and net2, respectively. The
/usr/share/doc/ifupdown/examples/ directory contains a mapping
script that can be used to select a logical interface based on the Media Access
Controller address (MAC address) of the adapter. First install the script to
an appropriate directory.
# install -m770 /usr/share/doc/ifupdown/examples/get-mac-address.sh \
/usr/local/sbin/
Then add a stanza like the following to /etc/network/interfaces:
mapping eth0
script /usr/local/sbin/get-mac-address.sh
map 02:23:45:3C:45:3C net1
map 00:A3:03:63:26:93 net2
See
Multi-stage mapping, Section 10.9
for a more complex example.
In applying either method the property that is most commonly used to identify
the adapter is the MAC address.
