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tools/oskit/doc/211bsd_ethernet.md

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+## Ethernet setup for 211bsd
+
+### Basic setup
+The w11a uses an emulated `DEUNA` interface which interacts via a _tap_
+device with the linux host system. The _tap_ device in turn is usually
+connected to an internal _bridge_. This way the w11a can exchange packets
+with the linux host as well as with any other node.
+
+### Setup of _tap_ and _bridge_
+The _tap_ device should be created such that it is accessible by the
+account under with _ti_w11_ executes. This way only setting up _tap_
+and _bridge_ require root access, but not subsequent usage.
+
+Two support scripts help in the setup
+```
+    ip_create_br
+```
+
+creates a bridge named _br0_ and re-connects the physical ethernet interface.
+The script works on a PC with a single physical Ethernet interface.
+```
+    ip_create_tap [tap-name]
+```
+
+add a user-mode _tap_ device to the bridge _br0_. If the bridge doesn't exist
+`ip_create_br` is called. If no name is given _tap0_ is used.
+
+### Used MAC addresses
+The MAC addresses used by w11a are
+```
+    52:65:74:72:6f:??
+```
+
+which are in the range of locally administered MAC addresses. The first
+five bytes mean in ASCII "Retro", easy to pick out in tcpdump -xx traces.
+
+### Setup in ti_w11
+Is contained in the boot tcl files, just three lines
+```
+    cpu0xua  set type deuna
+    cpu0xua  set dpa  retro:00
+    cpu0xua0 att tap:tap0
+```
+
+to select DEUNA emulation, the MAC address, and connect to _tap0_.
+
+### Setup in 211bsd
+The current setup is very simple, expects to live in a 192.168.2.* subnet,
+and does not use DNS, /etc/resolv.conf is empty, uses only /etc/hosts
+```
+    127.0.0.1       localhost
+    192.168.2.150   w11a
+    192.168.2.25    athome
+```
+
+The parameters in /etc/netstart are
+```
+    hostname=w11a
+    netmask=255.255.255.0
+    broadcast=192.168.2.255
+    default=192.168.2.1
+```
+