VM Networking¶

How to configure an experiment network

Overview¶

minimega uses software-defined networking to connect VMs on one or more virtual networks. These networks can span a single node, a cluster, or across clusters.

See Module 14 for more information about VM networking on a cluster.

APIs¶

This module covers the following APIs:

vm config networks
vlans
tap
bridge

Configuring networks¶

When configuring a VM, the user decides the bridge, VLAN, MAC, and driver for each VM interface. Endpoint VMs typically have a single interface while routers may have several.

vm config networks [netspec]...

Where netspec is:

<bridge>,<VLAN>,<MAC>,<driver>

Only the VLAN is mandatory -- the other fields have sane defaults.

What is a VLAN?¶

A VLAN is an extra 12-bit identifier in the MAC frame that logically separates LANs that share the same physical network.

VMs on the same VLAN are in the same LAN. VMs in different VLANs must be connected by a router that spans the VLANs.

The 12-bit identifier means that there are 4,094 possible VLANs. 0x000, 0xFFF, and 0x001 are typically reserved.

Configuring networks, examples¶

To connect a VM to VLANs 100 and 101:

vm config net 100 101

To connect a VM to VLANs 100 and 101 with specific mac addresses:

vm config net 100,00:00:00:00:00:00 101,00:00:00:00:01:00

To connect a VM to VLAN 100 on bridge0 and VLAN 200 on bridge1:

vm config net bridge0,100 bridge1,200

To connect a VM to VLAN 100 on bridge0 with a specific mac:

vm config net bridge0,100,00:11:22:33:44:55

To specify a specific driver, such as i82559c:

vm config net 100,i82559c

VLAN aliases¶

In the previous example, we used explicit VLAN identifiers like 100 and 101. minimega support VLAN aliases to make them easier to work with:

vm config net DMZ CORE

DMZ and CORE will automatically be assigned to an available VLAN identifier on their first use. Otherwise, they will mapped to the stored value.

VLAN aliases¶

The vlans API allows users to print, add, and configure VLAN aliases:

minimega$ vlans
alias | vlan
CORE  | 102
DMZ   | 101

You can manually add a VLAN using vlans add:

vlans add FOO 1000

To limit aliases to a particular identifier range, use vlans range.

VLAN blacklist¶

You may also blacklist identifiers that minimega should not use for new aliases:

minimega$ vlans blacklist 1000
minimega$ vlans blacklist
vlan
1000

This happens automatically if you specify a VLAN identifier in vm config networks:

minimega$ vm config net 1001
minimega[minimega]$ vlans blacklist
vlan
1000
1001

Creating host taps¶

Once VMs are running, it can be useful to access the VM network from the host. This is achieved by creating a host tap on the DMZ VLAN:

minimega$ tap create DMZ
mega_tap0

This interface can be given an IP using external tools or directly in minimega:

tap create DMZ ip 10.0.0.1/24

See this article for how to connect a VM to the Internet.

Mirrors and trunks¶

Accessing the "live" VM traffic can be useful to understand what the VMs are doing. There are two ways to do so: tap mirror and bridge trunk.

tap mirror mirrors one tap to another.

bridge trunk mirrors all traffic from the bridge to an interface.

See this article on tap mirroring for more information.

minimega also supports capturing packets. You can read up on the capture API in the API Documentation.

Next up…¶

Module 06: Experimental network