VLAN Tutorial

Next we are going to introduce VLANs.

ETA: ~30 mins.

Prerequisites

  • Install Faucet - Package installation steps 1 & 2
  • Install Open vSwitch - Connect your first datapath steps 1 & 2
  • Useful Bash Functions - Copy and paste the following definitions into your bash terminal, or to make them persistent between sessions add them to the bottom of your .bashrc and run ‘source .bashrc’.
create_ns () {
    NETNS=$1
    IP=$2
    sudo ip netns add ${NETNS}
    sudo ip link add dev veth-${NETNS} type veth peer name veth0 netns $NETNS
    sudo ip link set dev veth-${NETNS} up
    sudo ip netns exec $NETNS ip link set dev veth0 up
    sudo ip netns exec $NETNS ip addr add dev veth0 $IP
    sudo ip netns exec $NETNS ip link set dev lo up
}
as_ns () {
    NETNS=$1
    shift
    sudo ip netns exec $NETNS $@
}
cleanup () {
    for br in $(sudo ovs-vsctl list-br); do
        sudo ovs-vsctl del-br $br
    done
    IFS=$'\n';
    for i in  $(sudo ip netns list); do

        NS=$(echo $i | cut -d ' ' -f1)
        sudo ip netns delete $NS;
        # Sometimes the veth-$NS is not deleted.
        sudo ip link delete veth-$NS;
    done
}
  • to add a tagged network interface to a host namespaces
add_tagged_dev_ns () {
     NETNS=$1
     IP=$2
     VLAN=$3
     sudo ip netns exec $NETNS ip link add link veth0 name veth0.${VLAN} type vlan id $VLAN
     sudo ip netns exec $NETNS ip link set dev veth0.${VLAN} up
     sudo ip netns exec $NETNS ip addr flush dev veth0
     sudo ip netns exec $NETNS ip addr add dev veth0.${VLAN}  $IP
 }

Overview

In this tutorial we will look at how to do the following tasks using Faucet:

  • Use VLANs to segment traffic.
  • Create Trunk links.
  • ACLs for a particular VLAN.

Note

We cover Routing between VLANs in a later tutorial.

A port can be in several VLAN modes: 1. native - where packets come into the switch with no 802.1Q tag. 2. tagged - where packets come into the switch with a 802.1Q tag. 3. Both native and tagged.

If a packet comes in with a tag for a VLAN that the port is not configured for it will be dropped.

Configuring VLANs

To demonstrate these tasks we will use a demo network where a single switch br0 connects to 9 hosts.

Ports 1, 2, 5, 6 will be native (untagged) ports. While ports 3 & 4, 7 & 8, and 9 will be tagged ports.

Here is the structure of the demo setup.

VLAN Network Diagram

Tip

Keep a piece of paper with the network layout and hosts’ names, VLANs, IPs to simplify following the rest of the tutorial.

Network setup

Let’s start. Keep host1, host2 on the native vlan 100 (office vlan) as in the first and second tutorials.

Note

To create the hosts and switch again run

cleanup
create_ns host1 192.168.0.1/24
create_ns host2 192.168.0.2/24
sudo ovs-vsctl add-br br0 \
-- set bridge br0 other-config:datapath-id=0000000000000001 \
-- set bridge br0 other-config:disable-in-band=true \
-- set bridge br0 fail_mode=secure \
-- add-port br0 veth-host1 -- set interface veth-host1 ofport_request=1 \
-- add-port br0 veth-host2 -- set interface veth-host2 ofport_request=2 \
-- set-controller br0 tcp:127.0.0.1:6653 tcp:127.0.0.1:6654

Then add the following hosts with the corresponding vlan:

  • Assign host3 and host4 a vlan interface (vid:100) as they are on a tagged port.
  • Assign host5 and host6 an IP address from the VLAN 200 range.
  • Assign host7 and host8 a vlan interface (vid:300) as they are on a tagged port.
  • Add host9 to all vlans (100, 200, 300) to work as a NFV host.

Tagged vlan 100

create_ns  host3 0
create_ns  host4 0
add_tagged_dev_ns host3 192.168.0.3/24 100
add_tagged_dev_ns host4 192.168.0.4/24 100

Native vlan 200

create_ns  host5 192.168.2.5/24
create_ns  host6 192.168.2.6/24

Tagged vlan 300

create_ns  host7 0
create_ns  host8 0
add_tagged_dev_ns host7 192.168.3.7/24 300
add_tagged_dev_ns  host8 192.168.3.8/24 300

Trunk link for host9

create_ns  host9 0
add_tagged_dev_ns host9 192.168.0.9/24 100
add_tagged_dev_ns host9 192.168.2.9/24 200
add_tagged_dev_ns host9 192.168.3.9/24 300

Then connect all the hosts to the switch (br0)

sudo ovs-vsctl add-port br0 veth-host3 -- set interface veth-host3 ofport_request=3 \
-- add-port br0 veth-host4 -- set interface veth-host4 ofport_request=4 \
-- add-port br0 veth-host5 -- set interface veth-host5 ofport_request=5 \
-- add-port br0 veth-host6 -- set interface veth-host6 ofport_request=6 \
-- add-port br0 veth-host7 -- set interface veth-host7 ofport_request=7 \
-- add-port br0 veth-host8 -- set interface veth-host8 ofport_request=8 \
-- add-port br0 veth-host9 -- set interface veth-host9 ofport_request=9

Now we have everything to start working with faucet through its configuration file. Each time we will only need to change the configuration file and restart faucet (or send it HUP signal to reload the configuration file).

Basic vlan settings

Change /etc/faucet/faucet.yaml to reflect our setting.

/etc/faucet/faucet.yaml
vlans:
    vlan100:
        vid: 100
    vlan200:
        vid: 200
    vlan300:
        vid: 300
dps:
    sw1:
        dp_id: 0x1
        hardware: "Open vSwitch"
        interfaces:
            1:
                name: "host1"
                description: "host2 network namespace"
                native_vlan: vlan100
            2:
                name: "host2"
                description: "host2 network namespace"
                native_vlan: vlan100
            3:
                name: "host3"
                tagged_vlans: [vlan100]
            4:
                name: "host4"
                tagged_vlans: [vlan100]
            5:
                name: "host5"
                native_vlan: vlan200
            6:
                name: "host6"
                native_vlan: vlan200
            7:
                name: "host7"
                tagged_vlans: [vlan300]
            8:
                name: "host8"
                tagged_vlans: [vlan300]
            9:
                name: "host9"
                tagged_vlans: [vlan100,vlan200,vlan300]

Send SIGHUP signal to reload the configuration file, and check how its log the new configuration in /var/log/faucet/faucet.log

sudo systemctl reload faucet
cat /var/log/faucet/faucet.log

Let’s do the following simple tests:

  1. Ping between hosts in the same vlan
as_ns host1 ping 192.168.0.2
as_ns host3 ping 192.168.0.4
as_ns host5 ping 192.168.2.6
as_ns host7 ping 192.168.3.8

All should work.

  1. Ping between hosts in the same vlan where the port’s vlan mode is both native and tagged. In particular between host1 (native vlan100) to host3 (tagged vlan100).
as_ns host1 ping 192.168.0.3
  1. Ping between hosts in different vlans. Let’s change host5 (native vlan200) ip to be 192.168.0.5 and try to ping it from host1 (native vlan100).
as_ns host5 ifconfig veth0 192.168.0.5
as_ns host1 ping 192.168.0.5

It will not ping as they are in different vlans. Let’s set host5’s IP back.

as_ns host5 ifconfig veth0 192.168.2.5
  1. Test the trunk link to host9 from different vlans
as_ns host1 ping 192.168.0.9
as_ns host3 ping 192.168.0.9
as_ns host5 ping 192.168.2.9
as_ns host7 ping 192.168.3.9

All of this traffic should go through to host9 as it is connected through the trunk link.

Vlan ACL

Let’s apply an ACL on a particular vlan (e.g. vlan300). We will block any ICMP packets on vlan300. First create an ACL to block the ping. Open /etc/faucet/faucet.yaml and add the ‘acls’ section.

/etc/faucet/faucet.yaml
acls:
    block-ping:
        - rule:
            dl_type: 0x800      # IPv4
            ip_proto: 1         # ICMP
            actions:
                allow: False
        - rule:
            dl_type: 0x86dd     # IPv6
            ip_proto: 58        # ICMPv6
            actions:
                allow: False

Then apply this ACL on vlan300.

/etc/faucet/faucet.yaml
vlans:
    vlan100:
        vid: 100
        faucet_vips: ["192.168.0.254/24"]
    vlan200:
        vid: 200
        faucet_vips: ["192.168.2.254/24"]
    vlan300:
        vid: 300
        acls_in: [block-ping] # Acl apply only on vlan300

Just before we reload the configuration file. Let’s verify that pinging is working between hosts in vlan300.

as_ns host7 ping 192.168.3.8

Now let’s apply the configuration, send SIGHUP signal to reload the configuration file.

sudo systemctl reload faucet

Now if you try to ping from host7 and host8, it will not work as it is specified by their vlan acl.

as_ns host7 ping 192.168.3.8