[How to] Use tcpdump to look at LLDP packet

Here is an example about how to use tcpdump tool to look at LLDP information

> sudo tcpdump -c 1 -lv -v -i eth0 -a -e -s 1514 ether proto 0x88cc

The result:
tcpdump: listening on eth4, link-type EN10MB (Ethernet), capture size 1514 bytes
13:30:46.426056 08:00:27:09:61:e9 (oui Unknown) > 01:80:c2:00:00:0e (oui Unknown), ethertype LLDP (0x88cc), length 156: LLDP, length 142
    Chassis ID TLV (1), length 7
      Subtype MAC address (4): 08:00:27:09:61:e9 (oui Unknown)
      0x0000:  0408 0027 0961 e9
    Port ID TLV (2), length 7
      Subtype MAC address (3): 08:00:27:09:61:e9 (oui Unknown)
      0x0000:  0308 0027 0961 e9
    Time to Live TLV (3), length 2: TTL 120s
      0x0000:  0078
    System Name TLV (5), length 15: Ubuntu-Devstack
      0x0000:  5562 756e 7475 2d44 6576 7374 6163 6b
    System Description TLV (6), length 43
      Ubuntu 11.10\0x0a Linux 3.0.0-14-generic x86_64
      0x0000:  5562 756e 7475 2031 312e 3130 0a20 4c69
      0x0010:  6e75 7820 332e 302e 302d 3134 2d67 656e
      0x0020:  6572 6963 2078 3836 5f36 34
    System Capabilities TLV (7), length 4
      System  Capabilities [Bridge, WLAN AP, Router] (0x001c)
      Enabled Capabilities [Bridge, Router] (0x0014)
      0x0000:  001c 0014
    Management Address TLV (8), length 12
      Management Address length 5, AFI IPv4 (1): Ubuntu-Devstack.local
      Interface Index Interface Numbering (2): 5
      0x0000:  0501 c0a8 7a01 0200 0000 0500
    Port Description TLV (4), length 4: eth4
      0x0000:  6574 6834
    Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
      Link aggregation Subtype (3)
        aggregation status [supported], aggregation port ID 0
      0x0000:  0012 0f03 0100 0000 00
    Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
      MAC/PHY configuration/status Subtype (1)
        autonegotiation [supported, enabled] (0x03)
        PMD autoneg capability [10BASE-T hdx, 10BASE-T fdx, 100BASE-TX hdx, 100BASE-TX fdx, 1000BASE-T fdx] (0x6c01)
        MAU type 1000BASET fdx (0x001e)
      0x0000:  0012 0f01 036c 0100 1e
    Organization specific TLV (127), length 6: OUI IEEE 802.3 Private (0x00120f)
      Max frame size Subtype (4)
        MTU size 0
      0x0000:  0012 0f04 0000
    End TLV (0), length 0



The following is the argument list for reference:
 -a    將網絡地址和廣播地址轉變成名字
 -d    將匹配信息包的代碼以人們能夠理解的彙編格式給出
 -dd    將匹配信息包的代碼以c語言程序段的格式給出
 -ddd   將匹配信息包的代碼以十進制的形式給出
 -e    在輸出行打印出數據鏈路層的頭部信息
 -f    將外部的Internet地址以數字的形式打印出來
 -l    使標準輸出變為緩衝行形式( line buffered mode )
 -n    不把網絡地址轉換成名字
 -t    在輸出的每一行不打印時間戳
 -v    輸出一個稍微詳細的信息,例如在ip包中可以包括ttl和服務類型的信息
 -vv    輸出詳細的報文信息
 -c    在收到指定的包的數目後,tcpdump就會停止
 -F    從指定的文件中讀取表達式,忽略其它的表達式
 -i    指定監聽的網絡接口
 -r    從指定的文件中讀取包(這些包一般通過-w選項產生)
 -w    直接將包寫入文件中,並不分析和打印出來
 -T    將監聽到的包直接解釋為指定的類型的報文,常見的類型有rpc (遠程過程調用)和snmp(簡單網絡管理協議;)

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