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36.3. Virtualized Ethernet devices are not found by networking tools

The networking tools cannot identify the Xen Virtual Ethernet networking card inside the guest operation system. Verify this by executing the following (for Red Hat Enterprise Linux 4 and Red Hat Enterprise Linux 5):
cat /etc/modprobe.conf
Or (for Red Hat Enterprise Linux 3):
cat /etc/modules.conf
The output should contain the line and a similar line for each additional interface.
alias eth0 xen-vnif
To fix this problem you will need to add the aliasing lines (for example, alias eth0 xen-vnif) for every para-virtualized interface for the guest.