我在eth0上添加了一个标记的VLAN：
#ip link add link eth0 name eth0.20 type vlan id 20
这导致：
#ip link
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 9c:c7:a6:95:65:1c brd ff:ff:ff:ff:ff:ff
....
12: eth0.20@eth0: <BROADCAST,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 9c:c7:a6:95:65:1c brd ff:ff:ff:ff:ff:ff
#ip -d link show eth0.20
70: eth0.20@eth0: <BROADCAST,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 9c:c7:a6:95:65:1c brd ff:ff:ff:ff:ff:ff
vlan id 20 <REORDER_HDR>
#cat /proc/net/vlan/config
VLAN Dev name | VLAN ID
Name-Type: VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD
eth0.234 | 234 | eth0
eth0.20 | 20 | eth0
现在我开始dhclient：
#dhclient -d -v -1 eth0.20
我在tcpdump中看到的是一个未标记的DHCP发现帧：
#tcpdump -i eth0 -XX
0x0000: ffff ffff ffff 9cc7 a695 651c 0800 4500
^^^^
为什么没有标记？
似乎使用802.1q模块：
#lsmod | grep 8021q 8021q 28324 0 garp 14311 1 8021q
(OS：SLES11SP2内核3.0.13-0.27-默认)
10月16日更新
# tcpdump -Uw - | tcpdump -i eth0 -en -r - &
[1] 7310
# tcpdump: WARNING: eth0: no IPv4 address assigned
tcpdump: listening on eth0,link-type EN10MB (Ethernet),capture size 96 bytes
# dhclient -d -v -1 eth0.20
Internet Systems Consortium DHCP Client 4.2.3-P2
Copyright 2004-2012 Internet Systems Consortium.
All rights reserved.
For info,please visit https://www.isc.org/software/dhcp/
Listening on LPF/eth0.20/9c:c7:a6:95:65:1c
Sending on LPF/eth0.20/9c:c7:a6:95:65:1c
Sending on Socket/fallback
DHCPDISCOVER on eth0.20 to 255.255.255.255 port 67 interval 3
reading from file -,link-type EN10MB (Ethernet)
18:49:14.437882 9c:c7:a6:95:65:1c > ff:ff:ff:ff:ff:ff,ethertype IPv4 (0x0800),length 347: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP,Request from 9c:c7:a6:95:65:1c,length 305
^^^^^^
但实际上,在运行dhclient时,/ proc / net / dev中eth0.20的传输计数器确实会增加…
解决方法
由于VLAN加速,您无法在i686 / x86_64体系结构上看到来自tcpdump -i eth0输出的VLAN标记. VLAN层将由内核过滤,因此它总是看起来没有标记.请参考
Bug 498981 – tcpdump cannot deal with 802.1q vlan tag
tcpdump -i eth0 -Uw - | tcpdump -en -r - vlan 20
您应该看到以下输出：
<timestamp> <mac-addr-of-eth0> > Broadcast,ethertype 802.1Q (0x8100),length 346: vlan 20,p 0,ethertype IPv4,0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP
