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Brad
Asked: 2017-10-20 11:16:51 +0800 CST

How can I configure a NIC on a network with and without a bridge device for a VLAN at same time

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An am working with a CentOS 7 system which has a single physical Ethernet port which connects it to a network. This network primarily is on one subnet ("management network"), but also uses a tagged VLAN (VLAN 137) which has a separate subnet for VMs.

When configured "normally" - it appears and works on the management subnet.

However, I want to create a bridge device which connects to the same physical adapter, but for the bridge to use the 137 VLAN.

I can't figure out how to do this. I can either have the NIC on the normal (no tag) LAN, and I can create a bridge device, which is either on the (main) LAN or the VLAN. But I cannot figure out how to get the host on the "main" network and the bridge on the VLAN at the same time.

It appears as though a NIC can only be assigned to a single "bridge" at a time, and that one bridge can be assigned to a single VLAN, or no VLAN.

I'm obviously missing something. Any ideas?

(P.S. Preferably doing this without Network Manager - which I assume is a must).

networking

2 Answers

  1. Without using a bridge, I made the following test on virtual server, the server has eth0 configure.

    ip link add link eth0 name eth0.100 type vlan id 100
ip addr add 10.0.0.10/24 dev eth0.100
ip link set eth0.100 up

    If I try to ping google.it

    [root@localhost ~]# tcpdump -i any not port 22 -nne
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
17:49:34.880834 Out 52:54:00:c5:83:ad ethertype IPv4 (0x0800), length 71: 10.0.2.15.57014 > 10.0.2.3.53: 53728+ A? google.it. (27)
17:49:34.928806  In 52:54:00:12:35:02 ethertype IPv4 (0x0800), length 87: 10.0.2.3.53 > 10.0.2.15.57014: 53728 1/0/0 A 216.58.205.99 (43)
17:49:34.929356 Out 52:54:00:c5:83:ad ethertype IPv4 (0x0800), length 100: 10.0.2.15 > 216.58.205.99: ICMP echo request, id 28643, seq 1, length 64
17:49:34.946459  In 52:54:00:12:35:02 ethertype IPv4 (0x0800), length 100: 216.58.205.99 > 10.0.2.15: ICMP echo reply, id 28643, seq 1, length 64
17:49:34.947340 Out 52:54:00:c5:83:ad ethertype IPv4 (0x0800), length 88: 10.0.2.15.35452 > 10.0.2.3.53: 7858+ PTR? 99.205.58.216.in-addr.arpa. (44)
17:49:34.997721  In 52:54:00:12:35:02 ethertype IPv4 (0x0800), length 156: 10.0.2.3.53 > 10.0.2.15.35452: 7858 2/0/0 PTR mil04s26-in-f99.1e100.net., PTR mil04s26-in-f3.1e100.net. (112)

    If try to ping a host in the vlan subnet, you can see the vlan tag:

    [root@localhost ~]# tcpdump -i any not port 22 -nne
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
17:51:12.237624 Out 52:54:00:c5:83:ad ethertype ARP (0x0806), length 44: Request who-has 10.0.0.11 tell 10.0.0.10, length 28
17:51:12.237628 Out 52:54:00:c5:83:ad ethertype 802.1Q (0x8100), length 48: vlan 100, p 0, ethertype ARP, Request who-has 10.0.0.11 tell 10.0.0.10, length 28
17:51:13.238115 Out 52:54:00:c5:83:ad ethertype ARP (0x0806), length 44: Request who-has 10.0.0.11 tell 10.0.0.10, length 28
17:51:13.238123 Out 52:54:00:c5:83:ad ethertype 802.1Q (0x8100), length 48: vlan 100, p 0, ethertype ARP, Request who-has 10.0.0.11 tell 10.0.0.10, length 28
17:51:14.239809 Out 52:54:00:c5:83:ad ethertype ARP (0x0806), length 44: Request who-has 10.0.0.11 tell 10.0.0.10, length 28

    For me, you can have the management ip on the physical interface and the others ips on the vlan interfaces

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  2. Best Answer

    Following config takes one NIC - creates a VLAN interface for it - then adds a bridge device to both the original NIC and the VLAN interface

    ifcfg-br0

    BOOTPROTO="static"
DEFROUTE="yes"
NAME="br0"
DEVICE="br0"
ONBOOT="yes"
DNS1="10.244.53.108"
DNS2="10.245.177.15"
DOMAIN="dssdhop.lab.emc.com"
NM_CONTROLLED="no"
TYPE="Bridge"
IPADDR=10.244.141.171
PREFIX=24
GATEWAY=10.244.141.1
DNS1="10.244.53.108"

    ifcfg-br0.137

    BOOTPROTO="static"
DEFROUTE="yes"
NAME="br0.137"
DEVICE="br0.137"
ONBOOT="no"
DNS1="10.244.53.108"
DNS2="10.245.177.15"
DOMAIN="dssdhop.lab.emc.com"
NM_CONTROLLED="no"
TYPE="Bridge"
# Enable the following 3 IF you want to assign a local address to the host on this network
#IPADDR=10.244.137.54 
#PREFIX=24
#GATEWAY=10.244.137.1  – Generally don't want to specify a gatway - or it'll try using this as a default route!

    ifcfg-eno1

    TYPE=Ethernet
BOOTPROTO=none
NAME=eno1
UUID=8378a1f0-0330-45c8-bba6-7b77190cfb08
DEVICE=eno1
ONBOOT=yes
NM_CONTROLLED="no"
BRIDGE="br0"

    ifcfg-eno1.137

    DEVICE=eno1.137
VLAN=yes
ONBOOT=no
BRIDGE=br0.137
NM_CONTROLLED=NO
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