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The following table shows a simple example of how to create a virtual bridge on Linux and how to add TAP interfaces to it using ip commands:

StepCommand
Gather information about the existing network configuration.

List all existing interfaces, their status and their MAC addresses:
   # ip link show

List all configured IP addresses and netmasks:
   # ip addr show

List the routing table entries:
   # ip route show

Create a TAP interface (not needed if emulator automatic creation is used).

# ip tuntap add dev my_tap0 mod tap

Activate TAP interface (can also be done via the initialize command in emulator configuration).# ip link set my_tap0 up
Create a new bridge - if needed.# ip link add name my_bridge type bridge
Activate the bridge - if needed# ip link set my_bridge up
If needed, add a physical interface to the bridge. This interface will connect the bridge to the physical LAN.# ip link set <physical-int> master my_bridge
Remove any configured IP address from the physical interface.# ip addr delete <ip-address>/<netmask> dev <physical-int>
Add the IP address previously configured on the physical interface (or another IP address to be used by the host system) to the bridge interface.# ip addr add <ip-address>/<netmask> dev my_bridge
Add any routes (including the default gateway) to be routed across the bridge interface - if needed.

# ip route add <network>/<netmask> via <gwy-IP> dev my_bridge

# ip route add default via <gwy-IP> dev my_bridge

Add the TAP interface to the bridge (can also be done via the initialize command in the emulator configuration).# ip link set my_tap0 master my_bridge

Please note: The commands above are not persistent. They would need to be scripted and added to the host system startup as required.

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The following table shows a simple example of how to create a virtual bridge on Linux and how to add TAP interfaces to it using nmcli commands (NetworkManager command-line interface):

StepDescription
Gather information about the existing network configuration.


List all existing interfaces, their status and their MAC addresses:
   # ip link show

List all configured IP addresses and netmasks:
   # ip addr show

List the routing table entries:
   # ip route show

If needed, create a new connection for the physical interface to be used with the bridge.

# nmcli conn add type ethernet autoconnect yes \
con-name
<physical-int-name> \
ifname <pysical-int-name> ip4 0.0.0.0

If needed, create a bridge and set a static IP address for it.# nmcli con add type bridge autoconnect yes \
con-name
mybr0 ifname mybr0  \
ipv4.method manual ip4
<ipaddr/mask> stp off
If needed, activate bridge.# nmcli con up bridge-mybr0
If needed, add physical interface to bridge.# nmcli conn modify <physical-int-conn> master mybr0 \
slave-type bridge
Activate changes to interface.# nmcli conn up <physical-int-conn>

After the bridge has been created, you can use the initialize command in the emulator configuration to add the required TAP interfaces for the emulator to the bridge.

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