二台のサーバをGRE(Generic Routing Encapsulation)を使用したL2トンネルで接続し、その中にタグVLANを流す方法です。
タグVLANの使用できないネットワーク越しのKVMホスト間を接続する際に使用しました。

#構成

NICは192.168.0.0/24のIPアドレスを割り当てる
両サーバでブリッジ(br_dmz,br_lan)を作成する

#やりたいこと
両サーバのブリッジをそれぞれ同じL2ネットワークにしたい

#設定

##SV1側設定

createTunnel_sv1.sh

#!/bin/sh

# 1528 = 1500 + 4(VLANタグ) + 24(GREヘッダ)
ifconfig eth0 mtu 1528

# ---------------------------------------------------------
# GREトンネル作成(gre0とかgretap0だと上手くいかない気がする)
# ---------------------------------------------------------
modprobe ip_gre
ip link add name gretunnel type gretap remote 192.168.0.2
ip link set gretunnel up
ip link set gretunnel mtu 1504

# ---------------------------------------------------------
# VLAN設定
# ---------------------------------------------------------
ip link add link gretunnel name vlan_dmz type vlan id 101
ip link set vlan_dmz up
ip link set vlan_dmz mtu 1500
ip link add link gretunnel name vlan_lan type vlan id 102
ip link set vlan_lan up
ip link set vlan_lan mtu 1500

# ---------------------------------------------------------
#ブリッジ作成
# ---------------------------------------------------------
brctl addbr br_dmz
ip addr add 10.4.0.1/24 dev br_dmz
ip link set br_dmz up

brctl addbr br_lan
ip addr add 10.5.0.1/24 dev br_lan
ip link set br_lan up

# ---------------------------------------------------------
#ブリッジにVLANを割り当て
# ---------------------------------------------------------
brctl addif br_dmz vlan_dmz
brctl addif br_lan vlan_lan

##SV2側設定

createTunnel_sv2.sh

#!/bin/sh

ifconfig eth0 mtu 1500

# ---------------------------------------------------------
# GREトンネル作成
# ---------------------------------------------------------
modprobe ip_gre
ip link add name gretunnel type gretap remote 192.168.0.1
ip link set gretunnel up
ip link set gretunnel mtu 1462

# ---------------------------------------------------------
#VLAN設定
# ---------------------------------------------------------
ip link add link gretunnel name vlan_dmz type vlan id 101
ip link set vlan_dmz up
ip link set vlan_dmz mtu 1458
ip link add link gretunnel name vlan_lan type vlan id 102
ip link set vlan_lan up
ip link set vlan_lan mtu 1458

# ---------------------------------------------------------
#ブリッジ作成
# ---------------------------------------------------------
brctl addbr br_dmz
ip addr add 10.4.0.2/24 dev br_dmz
ip link set br_dmz up

brctl addbr br_lan
ip addr add 10.5.0.2/24 dev br_lan
ip link set br_lan up

# ---------------------------------------------------------
#ブリッジにVLANを割り当て
# ---------------------------------------------------------
brctl addif br_dmz vlan_dmz
brctl addif br_lan vlan_lan

#確認
インターフェースの状態を確認(関係のある部分のみ抜粋)

sv02

# ip a
3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.2/24 brd 192.168.0.255 scope global eth1
       valid_lft forever preferred_lft forever
7: gre0: <NOARP> mtu 1476 qdisc noop state DOWN
    link/gre 0.0.0.0 brd 0.0.0.0
8: gretap0: <BROADCAST,MULTICAST> mtu 1476 qdisc noop state DOWN qlen 1000
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
9: gretunnel@NONE: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1462 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
       valid_lft forever preferred_lft forever
10: vlan_dmz@gretunnel: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1458 qdisc noqueue state UP
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
       valid_lft forever preferred_lft forever
11: vlan_lan@gretunnel: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1458 qdisc noqueue state UP
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
       valid_lft forever preferred_lft forever
12: br_dmz: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1458 qdisc noqueue state UNKNOWN
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
    inet 10.4.0.2/24 scope global br_dmz
       valid_lft forever preferred_lft forever
13: br_lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1458 qdisc noqueue state UNKNOWN
    link/ether **:**:**:**:**:** brd ff:ff:ff:ff:ff:ff
    inet 10.4.1.2/24 scope global br_lan
       valid_lft forever preferred_lft forever

GRE上のVLAN上でICMPのやりとりが行われていることを確認

sv01

$ sudo ping  -d -M do -s 1430 10.4.0.2

sv02


22:41:19.392715 d4:3d:7e:0a:4a:dd > d4:3d:7e:0a:49:bf, ethertype IPv4 (0x0800), length 1514: 192.168.0.1 > 192.168.0.2: GREv0, proto TEB (0x6558), length 1480: 1a:60:64:59:e2:28 > b6:7d:da:4c:cc:29, ethertype 802.1Q (0x8100), length 1476: vlan 101, p 0, ethertype IPv4, 10.4.0.1 > 10.4.0.2: ICMP echo request, id 51530, seq 5, length 1438
	0x0000:  4500 05dc 3b89 4000 402f 7816 c0a8 0001  E...;.@.@/x.....
	0x0010:  c0a8 0002 0000 6558 b67d da4c cc29 1a60  ......eX.}.L.).`
	0x0020:  6459 e228 8100 0065 0800 4500 05b2 0000  dY.(...e..E.....
	0x0030:  4000 4001 2141 0a04 0001 0a04 0002 0800  @.@.!A..........
	0x0040:  8bd5 c94a 0005 7f7d b254 0000 0000 1efb  ...J...}.T......
	0x0050:  0500 0000 0000 1011 1213 1415 1617 1819  ................
	0x0060:  1a1b 1c1d 1e1f 2021 2223 2425 2627 2829  .......!"#$%&'()
	0x0070:  2a2b 2c2d 2e2f 3031 3233 3435 3637 3839  *+,-./0123456789
	(略)
	0x05b0:  6a6b 6c6d 6e6f 7071 7273 7475 7677 7879  jklmnopqrstuvwxy
	0x05c0:  7a7b 7c7d 7e7f 8081 8283 8485 8687 8889  z{|}~...........
	0x05d0:  8a8b 8c8d 8e8f 9091 9293 9495            ............
22:41:19.392754 d4:3d:7e:0a:49:bf > d4:3d:7e:0a:4a:dd, ethertype IPv4 (0x0800), length 1514: 192.168.0.2 > 192.168.0.1: GREv0, proto TEB (0x6558), length 1480: b6:7d:da:4c:cc:29 > 1a:60:64:59:e2:28, ethertype 802.1Q (0x8100), length 1476: vlan 101, p 0, ethertype IPv4, 10.4.0.2 > 10.4.0.1: ICMP echo reply, id 51530, seq 5, length 1438
	0x0000:  4500 05dc 6455 4000 402f 4f4a c0a8 0002  E...dU@.@/OJ....
	0x0010:  c0a8 0001 0000 6558 1a60 6459 e228 b67d  ......eX.`dY.(.}
	0x0020:  da4c cc29 8100 0065 0800 4500 05b2 8657  .L.)...e..E....W
	0x0030:  0000 4001 dae9 0a04 0002 0a04 0001 0000  ..@.............
	0x0040:  93d5 c94a 0005 7f7d b254 0000 0000 1efb  ...J...}.T......
	0x0050:  0500 0000 0000 1011 1213 1415 1617 1819  ................
	0x0060:  1a1b 1c1d 1e1f 2021 2223 2425 2627 2829  .......!"#$%&'()
	0x0070:  2a2b 2c2d 2e2f 3031 3233 3435 3637 3839  *+,-./0123456789
	(略)
	0x05b0:  6a6b 6c6d 6e6f 7071 7273 7475 7677 7879  jklmnopqrstuvwxy
	0x05c0:  7a7b 7c7d 7e7f 8081 8283 8485 8687 8889  z{|}~...........
	0x05d0:  8a8b 8c8d 8e8f 9091 9293 9495            ............

上記PING送信時のイーサネットフレーム

   14Byte         20Byte     4Byte    14Byte       4Byte       20Byte        8Byte     (1430Byte)
|ETH_HEADER] [GRE_IP_HEADER] [GRE] [ETH_HEADER] [802.1Q_TAG] [IP_HEADER] [ICMP_HEADER] [ICMP_DATA]
|            |               |     |            |            |           |(1438)-----------------|
|            |               |     |            |            |(1458)"vlan_lan" MTU SIZE ---------|
|            |               |     |            |(1462)"gretunnel" MTU SIZE ---------------------|
|            |               |     |(1476)-------------------------------------------------------|
|            |               |(1480)-------------------------------------------------------------|
|            |(1500)"eth0" MTU SIZE -------------------------------------------------------------|
|(1514)Ethernet Frame Size ----------------------------------------------------------------------|