Distribution:

RedHat 9.0
Hardware Environment:

ThinkPad R40, 
eth0 device
  bus: PCI
  driver: e100
  desc: "Intel Corp.|82801BD PRO/100 VE (MOB) Ethernet Controller"
  vendorId: 8086
  deviceId: 103d
  subVendorId: 1014
  subDeviceId: 0522
  pciType: 1

Software Environment:

2.4.x, lately tested in 2.4.22-ac4, also the RedHat's kernels suffer from this
problem.

Problem Description:

When a bridge is build over the eth0 and tap0 (driven by tun module) everything
works well until the eth0 cabel is physicaly plugged into the hub. After that I
get kernel panic (the blinking capslock LED).

Steps to reproduce:

Get tun driver using software (creating the tap0 nif - I use this
http://aranym.sf.net) and create a bridge over the real eth0 you are using to go
out and the tap0. Plug the eth0 cabel into the hub. You should get kernel panic.