当我们想在操作系统里面查看网口和交换机连接的状态信息，我们可以使用lldptool这个工具。

LLDP是一个数据链路层发现协议，LLDP协议使得接入网络的一台设备可以将其主要的能力，管理地址，设备标识，接口标识等信息发送给接入同一个局域网络的其它设备。lldptool工具采用的是LLDP协议，一般我们使用lldptool是为了得到设备的物理拓扑结构以及管理配置信息，比如说，和eth1网口相连的网络交换机的Vlan ID是多少？网络交换机的名称是什么？网线插在网络交换机的什么地方？

在这里我们不去讨论LLDP协议的架构和具体时序状态码等，这里仅仅介绍怎么用它。

LLDP协议有四种工作模式：

• TxRx：既发送也接收LLDP 帧
• Tx    ：只发送不接收LLDP 帧
• Rx：只接收不发送LLDP 帧
• Disable：既不发送也不接收

一般设置LLDP工作在TxRx模式。

lldptool [options] [参数]

Options

-i [ifname]

specifies the network interface to which the command applies

-V [tlvid]

specifies the TLV identifier
The tlvid is an integer value used to identify specific LLDP TLVs. The tlvid value is the Type value for types not equal to 127 (the organizationally specific type). For organizationally specific TLVs, the tlvid is the value represented by the 3 byte OUI and 1 byte subtype - where the subtype is the lowest order byte of the tlvid.
The tlvid can be entered as a numerical value (e.g. 10 or 0xa), or for supported TLVs, as a keyword. Review the lldptool help output to see the list of supported TLV keywords.

-n

"neighbor" option for commands which can use it (e.g. get-tlv)

-g [bridge scope]

specify the bridge scope this command operates on. Allows to set and query all LLDP TLV modules for "nearest_bridge" (short: "nb"), "nearest_customer_bridge" ("ncb") and "nearest_nontpmr_bridge" ("nntpmrb") group mac addresses. Configurations are saved into independent sections in lldpad.conf. If no bridge scope is supplied this default to "nearest bridge" to preserve the previous behaviour.

-c

"config" option for TLV queries. Indicates that the query is for the configuration elements for the specified TLV. The argument list specifies the specific elements to query. If no arguments are listed, then all configuration elements for the TLV are returned.

-r

show raw client interface messages

-R

show only raw Client interface messages

Commands

license

show license information

-h, help

show usage information

-v, version

show version information

-S, stats

get LLDP statistics

-t, get-tlv

get TLV information

-T, set-tlv

set TLV information

-l, get-lldp

get LLDP parameters

-L, set-lldp

set LLDP parameters

-q, quit

exit from interactive mode

ip a查看启用网口：

先看一些有没有lldptool工具，如果没有的话yum装一下：

[root@wow ~]# service lldpad status
lldpad is stopped
[root@wow ~]# service lldpad start
Starting lldpad: [ OK ]
[root@wow ~]#

先设置lldptool的工作模式：

[root@wow ~]# lldptool set-lldp -i eth0 adminStatus=rxtx
adminStatus = rxtx　　#这样就和网络交换机建立了邻居关系，接下来就可以查询连接的交换机信息了

使用lldptool查看网口与交换机连接状态：

[root@wow ~]# lldptool -t -n -i eth0
Chassis ID TLV
MAC: :xx:xx:xx:xx:51　　#mac地址
Port ID TLV
Ifname: GE1//1　　　　#网线插在交换机上的端口位置
Time to Live TLV

System Name TLV
xx-xx-CE5850-xxxxx　　#交换机设备名
System Description TLV
Huawei Versatile Routing Platform Software
VRP (R) software, Version 8.150 (CE5855EI V200R002C50SPC800)
Copyright (C) - Huawei Technologies Co., Ltd.
HUAWEI CE5855-xxxx-xxx　　#华为的交换机

System Capabilities TLV
System capabilities: Bridge, Router
Enabled capabilities: Bridge, Router
Management Address TLV
IPv4: xx.xxx.xxx.xx　　#ip地址
Ifindex:
OID: +[)
Port VLAN ID TLV
PVID:
Port and Protocol VLAN ID TLV
PVID: , not supported, not enabled
VLAN Name TLV
VID : Name VLAN3652
MAC/PHY Configuration Status TLV
Auto-negotiation supported and enabled
PMD auto-negotiation capabilities: 0xxxxx
MAU type: BaseXFD
Link Aggregation TLV
Aggregation capable
Currently not aggregated
Aggregated Port ID:
Maximum Frame Size TLV

End of LLDPDU TLV
[root@wow ~]#

如果想利用lldptool对网口进行一些设置，可以参考手册，下面是在Linux上找男人看到的一些例子：

Configure LLDP adminStatus to Receive and Transmit for interface eth2　　#为网口eth2配置LLDP的收发工作模式
lldptool -L -i eth2 adminStatus=rxtx
lldptool set-lldp -i eth2 adminStatus=rxtx

Disable the LLDP adminStatus for all interfaces　　#让所有网口都不可用LLDP
lldptool set-lldp adminStatus=disabled
Query the LLDP adminStatus for interface eth3　　#查询网口eth3的LLDP状态
lldptool -l -i eth3 adminStatus
lldptool get-lldp -i eth3 adminStatus

Query the LLDP statistics for interface eth3 　　#查询网口eth3的统计信息
lldptool -S -i eth3 adminStatus
lldptool stats -i eth3 adminStatus

Query the local TLVs which are being transmitted for a given interface: 　　#查询为给定接口传输的本地
lldptool -t -i eth3
lldptool get-tlv -i eth3

Query the received neighbor TLVs received on a given interface:　　#查询给定接口上收到的接收邻居TLV
lldptool -t -n -i eth3
lldptool get-tlv -n -i eth3

Query the value of the System Description TLV as received from the neighbor on a given interface:
lldptool -t -n -i eth3 -V sysDesc
lldptool get-tlv -n -i eth3 -V

Disable transmit of the IEEE 802.3 MAC/PHY Configuration Status TLV for a given interface:
lldptool -T -i eth3 -V macPhyCfg enableTx=no
lldptool set-tlv -i eth3 -V 0x120f01 enableTx=no

Enable transmit of the Port Description TLV for all interfaces:
lldptool -T -V portDesc enableTx=yes
lldptool set-tlv -V enableTx=yes

Query value of the transmit setting for the Port Description TLV for a given interface:
lldptool -t -V portDesc -c enableTx
lldptool get-tlv -V -c enableTx

Set a Management Address TLV on eth3 to carry IPv4 address 192.168.10.10
lldptool -T -i eth3 -V mngAddr ipv4=192.168.10.10
Set a Management Address TLV on eth3 to carry IPv6 address ::192.168.10.10
lldptool -T -i eth3 -V mngAddr ipv6=::192.168.10.10

Get the configured IPv4 address for the Management Address TLV on eth3

lldptool -t -i eth3 -V mngAddr

c ipv4

Get all configured attributes for the Management Address TLV on eth3
lldptool -t -i eth3 -V mngAddr -c
Query the current DCBX mode that will be used if lldpad is restarted. (this is not a persistent setting)

lldptool

t -i eth3 -V IEEE-DCBX -c mode

Reset the DCBX mode to be 'auto' (start in IEEE DCBX mode) after the next lldpad restart
lldptool -T -i eth3 -V IEEE-DCBX mode=reset
Enable transmit of the Edge Virtual Bridging TLV for interface eth4

lldptool

i eth4 -T -V evbCfg enableTx=yes

Configure EVB TLV to set reflective relay and RTE,ECP and VDP capabilities
lldptool -T -i eth4 -V evbCfg fmode=reflectiverelay
lldptool -T -i eth4 -V evbCfg capabilities=rte,ecp,vdp

Enable transmit of the VDP for interface eth4
lldptool -i eth4 -T -V vdp enableTx=yes
Configurations per port have higher precedence than global configurations.