and FreeBSD. Though I've also needed to set them up under Linux, I
never seemed to get around to writing up how to do so. To remedy this,
the following are our setup details:
HOST: tux PROMPT: tux [0] LINUX DISTRO: CentOS 5.4 (Red Hat EL clone) INTERFACE: eth0 VLANs: 487 (7.7.4.0/23), 519 (10.19.3.0/24)To get started, VLAN tagging (802.1q trunking) has been supported by Linux
for a while, first as a patch, then included in the kernel since 2.4.14.
Given that the following details the setup on CentOS 5.4, the specifics
for config retention through a reboot may be different for other distros.
The command line syntax should be about the same, though. To ensure
that the Linux kernel supports VLAN tagging, check for the kernel module
(8021q), and if necessary, load it:
tux [0] /sbin/lsmod | /bin/grep 8021q tux [1] /sbin/modprobe 8021q tux [0] /sbin/lsmod | /bin/grep 8021q 8021q 24649 0In the above, since the first 'lsmod' didn't report the 8021q module,
we had loaded it via 'modprobe' and the second 'lsmod' verifies such.
It isn't explicitly necessary to load the module as configuration of
a VLAN tagged interface should take care of it. The purpose above is
to simply identify kernel support for 802.1q trunking. Assuming that the
network switch port that our interface is connected to has already been
configured to support VLAN trunking, we can add a couple of VLANs (487
and 519) to the network interface (eth0) on our host (tux):
tux [0] /sbin/vconfig add eth0 487 ERROR: trying to add VLAN #487 to IF -:eth0:- error: Invalid argumentThe error above is because interface 'eth0' is not up, so we'll need to
try again:
tux [3] /sbin/ifconfig eth0 up tux [0] /sbin/vconfig add eth0 487 Added VLAN with VID == 487 to IF -:eth0:- tux [0] /sbin/vconfig add eth0 519 Added VLAN with VID == 519 to IF -:eth0:-Now that the new interfaces are configured, we can identify them in
'ifconfig' output and configure them much like a normal interface:
tux [0] /sbin/ifconfig -a | /bin/awk '/^eth0/ {print $1}'
eth0
eth0.487
eth0.519
tux [0] /sbin/ifconfig eth0.487 7.7.4.129 netmask 255.255.254.0 up
tux [0] /sbin/ifconfig eth0.519 10.19.3.78 netmask 255.255.255.0 up
tux [0] /sbin/ifconfig -a
eth0 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:2736 (2.6 KiB)
Interrupt:169 Base address:0xd020
eth0.487 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8
inet addr:7.7.4.129 Bcast:7.7.5.255 Mask:255.255.254.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
eth0.519 Link encap:Ethernet HWaddr 08:00:27:9E:A8:A8
inet addr:10.19.3.78 Bcast:10.19.3.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
<snip...>
As seen above, the supporting interface (eth0) doesn't need to beconfigured, only brought up in order to support a trunked interface.
As an aside, Linux retains a listing of the VLAN interface name, the VLAN
ID, and the supporting device listed in file '/proc/net/vlan/config'.
Linux also retains various statistics regarding the VLAN interface
name (ex: eth0.487) in unique interface files in the same directory.
The following is a sample of this:
tux [0] /bin/cat /proc/net/vlan/config VLAN Dev name | VLAN ID Name-Type: VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD eth0.487 | 487 | eth0 eth0.519 | 519 | eth0 tux [0] /bin/cat /proc/net/vlan/eth0.487 eth0.487 VID: 487 REORDER_HDR: 1 dev->priv_flags: 81 total frames received 0 total bytes received 0 Broadcast/Multicast Rcvd 0 total frames transmitted 0 total bytes transmitted 0 total headroom inc 0 total encap on xmit 0 Device: eth0 INGRESS priority mappings: 0:0 1:0 2:0 3:0 4:0 5:0 6:0 7:0 EGRESSS priority Mappings:The only thing left now is to configure our bootup scripts to retain
our configuration:
tux [0] cd /etc/sysconfig/network-scripts/ tux [0] /bin/cat ifcfg-eth0 # Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE] DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=no TYPE=Ethernet HWADDR=08:00:27:9e:a8:a8The config file for 'eth0' gets updated to:
tux [0] /bin/cat ifcfg-eth0 DEVICE=eth0 BOOTPROTO=none ONBOOT=yes TYPE=Ethernet HWADDR=08:00:27:9e:a8:a8Additionally, after creating 'ifcfg-eth0.487', the contents are:
tux [0] /bin/cat ifcfg-eth0.487 # vlan 487, 7.7.4.0/23 DEVICE=eth0.487 ONBOOT=yes TYPE=Ethernet IPADDR=7.7.4.129 NETWORK=7.7.4.0 NETMASK=255.255.254.0 BROADCAST=7.7.5.255 VLAN=yesAnd for interface 'eth0.519':
tux [0] /bin/cat ifcfg-eth0.519 # vlan 519, 10.19.3.0/24 DEVICE=eth0.519 ONBOOT=yes TYPE=Ethernet IPADDR=10.19.3.78 NETWORK=10.19.3.0 NETMASK=255.255.255.0 BROADCAST=10.19.3.255 VLAN=yes
