vlan 抓包分析

时间 2020-01-24

标签 vlan 抓包分析繁體版

原文原文链接

# vlan (virtual LAN )
# 一台未设置任何VLAN的二层交换机上，任何广播帧都会被转发给除接收端口外的全部其余端口（Flooding）。VLAN经过限制广播帧转发的范围分割了广播域
# 802.1Q也即“Virtual Bridged Local Area Networks”（虚拟桥接局域网，简称“虚拟局域网”）协议，公有协议
# ISL&DISL思科交换链路内协议和动态 ISL协议（ISL & DISL:Cisco Inter-Switch Link Protocol and Dynamic ISL Protocol） 交换链路内协议（ISL），是思科私有协议
# 802.1Q和ISL主要区别：
# ISL 思科私有标准，只用于思科设备之间互联，在数据帧头部和尾部封装30byte的开销；
# 802.1Q 国际标准协议，适用于各个厂商生产的交换机，在数据帧内部增长4byte的开销；

# 以太网帧结构和802.1Q帧结构
# 以太网帧格式
 |-----------------------------------------------------------------------------|
 | DMAC(6bytes) | SMAC(6bytes) | Ether-Type(2bytes) | DATA |
 |-----------------------------------------------------------------------------|
# 802.1Q 以太网帧格式
 |--------------------------------------------------------------------------------------------|
 | DMAC(6bytes) | SMAC(6bytes) | Ether-Type(0x8100)| VLAN(4bytes) | Ether-Type(2bytes) | DATA |
 |--------------------------------------------------------------------------------------------|

 # VLAN TAG的格式
 |--------------------------------------------------------------------------------------|
 | Ether-Type(0x8100)| PRI(3bits) | CFI(1bit) | TAG(12bits) | Ether-Type(2bytes) | DATA |
 |--------------------------------------------------------------------------------------|
# PRI：帧优先级，就是一般所说的802.1p，(LAN Layer 2 QoS/CoS Protocol for Traffic Prioritization ) 有关流量优先级LAN第二层QoS/CoS协议
# 1(background),0(默认，没有优先级),2 (excellent effort),3(关键应用),4 (视频),5 (语音),6 (网间控制),7 (网络控制)
# CFI：规范标识位，0为规范格式，用于802.3或EthII。1为非规范格式，它被用在令牌环/源路由FDDI介质访问方法中来指示封装帧中所带地址的比特次序信息
# TAG：就是咱们一般说的VLAN ID，12bit，指明VLAN的ID，一共4096个
# 12bit 0-4095
#  1:系统vlan
#  2-1001:以太vlan
#  1002/1003/1004/1005: tocken ring
#  1006-2095:扩展vlan vtp3 vtp1/2 transparant
# Ether-Type：标识紧随其后的数据类型。

# VLAN TAG处理过程
# PC    ：大部分的PC（专用的，或用于测试的除外）是工做在应用层的，缺省状况下是不支持(其实也不须要)VLAN TAG的。也就是说，PC发出的都是UNTAGED数据帧。

# Router：路由器是支持VLAN TAG的。也就是说，路由器能够发出TAGED数据帧，也能够发出UNTAGED数据帧。须要说明的是，路由器是处理数据包的三层信息的，对于二层信息#        （包括VLAN信息），路由器只是检查其有效性，以后将其剥离。这个过程就是咱们常说的‘终结’，也就是说，路由器会终结掉报文的VLAN信息的。

# Switch：以太网交换机。VLAN技术就是主要针对于交换机提出的，因此，在讨论VLAN概念时都是立足于交换机来讨论。很显然，交换机既支持收发TAGED数据帧，
#        也支持收发UNTAGED数据帧。从严格意义上讲，引入VLAN后，交换机的行为再也不是‘透明传输’，由于数据帧通过交换机后可能发生了变化。

# 全部能感知VLAN的交换机，报文在交换机内部转发过程当中都是带Tag的。在交给交换芯片处理以前，或者交换芯片交给端口时会根据端口的设置添加或去掉Tag。
# 若是没有进行配置，默认全部的端口都处于Access模式。通常来讲，对端口来讲与VLAN相关的有三个属性，PVID、Tag Vlan、Untag Vlan。PVID有且只有一个，Tag Vlan和Untag Vlan可能有一个，多个，也能够没有，但两个至少其中一个有一个。

# PVID的做用是：若是此端口收到一个Untag的报文，则交换机会根据PVID的值给此报文打上等于PVID的Tag，而后交给交换芯片处理；若是交换芯片要将一个报文今后端口发送，发现此报文的Tag值与PVID相同，则会将Tag去掉，而后今后端口发送出去。

# Tag Vlan和Untag Vlan主要是用于报文发送的处理，若是交换芯片要将报文今后端口发送，发现报文的Tag在此端口的Tag Vlan中，且不等于PVID，则此报文将以Tag的形式发送出去，若是在Untag Vlan中，则以Untag形式发出去。若是报文的Tag既不在Tag Vlan中，也不在Untag Vlan中，则只有一种可能，交换芯片出毛病了。这就是交换机处理Vlan Tag的基本原则了。能够如图所示，即Tag处理只在交换芯片的进、出时刻。


# 若是是Trunk，端口只能有一个Untag的VLAN，且其等于PVID，有多个Tag的VLAN。端口能够接收在全部容许的VLAN和Untag的报文，若是是Untag的报文，则在PVID所在的VLAN转发。报文发送时，按上述规则转发，便可能是Tag的，也多是Untag的。
# 交换机互联为trunk模式
IOU1#interface Ethernet3/3
IOU1#switchport trunk encapsulation dot1q
IOU1#switchport mode trunk
IOU1#duplex auto

IOU1(config-if)#do sh int e3/3 swi
Name: Et3/3
Switchport: Enabled
Administrative Mode: trunk    
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Appliance trust: none

IOU2#interface Ethernet3/3
IOU2#switchport trunk encapsulation dot1q
IOU2#switchport mode trunk
IOU2#duplex auto

-------------------------------------------------------------------------------------------------------------------
1.1.1.3 ----> | access vlan 10 |-----|     trunk      |---->|     trunk      |-----| access vlan 10 |----> 1.1.1.6
              |     port1      | SW1 |     port2      |     |     port1      | SW1 |     port2      |      
-------------------------------------------------------------------------------------------------------------------

# 一、路由R3 发出 UNTAGED 以太帧
Frame 37: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00), Dst: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Destination: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Source: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00)
    Type: IPv4 (0x0800)    # 
Internet Protocol Version 4, Src: 1.1.1.1, Dst: 1.1.1.3
Internet Control Message Protocol

# 二、从SW1 access vlan 10口进入，并从SW1 trunk 口出
Frame 96: 118 bytes on wire (944 bits), 118 bytes captured (944 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00), Dst: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Destination: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Source: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10    
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10        
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.1, Dst: 1.1.1.3
Internet Control Message Protocol

# 三、从SW2 trunk 口入，并从SW2 access vlan 10 口出
Frame 29: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00), Dst: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Destination: aa:bb:cc:00:04:00 (aa:bb:cc:00:04:00)
    Source: aa:bb:cc:00:06:00 (aa:bb:cc:00:06:00)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.1, Dst: 1.1.1.3
Internet Control Message Protocol


# 若是是Access，端口只能有一个VLAN Tag，且其等于PVID，没有tag的VLAN。所以Access端口只能接收Untag的报文或所属的VLAN，即等于PVID的VLAN。出去的报文都是Untag的。
# 交换机互联为access模式
-------------------------------------------------------------------------------------------------------------------
1.1.1.3 ----> | access vlan 10 |-----| access vlan 10 |---->| access vlan 10 |-----| access vlan 10 |----> 1.1.1.6
              |     port1      | SW1 |     port2      |     |     port1      | SW1 |     port2      |      
-------------------------------------------------------------------------------------------------------------------

# 一、路由R3 发出 UNTAGED 以太帧
Frame 169: 60&n鈙p;b9teq on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:07:00 (aa:bb:cc:00:07:00), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:07:00 (aa:bb:cc:00:07:00)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

# 二、从SW1 access vlan 10口进入，并从SW1 access vlan 10 口出
Frame 296: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:07:00 (aa:bb:cc:00:07:00), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:07:00 (aa:bb:cc:00:07:00)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

# 二、从SW2 access vlan 10口进入，并从SW2 access vlan 10 口出
Frame 151: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:07:00 (aa:bb:cc:00:07:00), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:07:00 (`a:b:cg:00:07:00)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

# native vlan 
# Native VLAN是trunk上才有的概念.主要的目的是不丢弃非标记帧.接收方交换机把全部接收到的未标记的数据包转发到NATIVE VLAN中,而不是丢弃.默认是VLAN1.
# trunk native vlan只对Untag帧加pvid，对tag pvid的帧去除pvid

801.q的TRUNK中能够存在多个VLAN。各个VLAN都被加上一个头，并在该头部说明VLAN号码,可是有一个VLAN，不加头，不进行封装。就是native vlan。交换机在发送数据时候会使用vlan的标记来标记该数据属于哪一个vlan，802.1Q容许一个不打标记的vlan，凡在这个segement上没有打标记，对端交换机读数据时候没有读到802.1Q的标记则认为是native vlan
简单的来讲Native Vlan 是802。1Q协议封装下的一种特殊Vlan,来自该VLAN的流量在穿越TRUNK接口时不打TAG，缺省时VLAN1为Native Vlan .
 而VLAN1 为交换机的缺省VLAN，通常不承载用户DATA也不承载管理流量，只承载控制信息：如CDP，DTP，BPDU，VTP，Pagp等。
 
# arp request： 
------------------------------------------------------------------------------------------------------------------------------------
1.1.1.4 ----> | trunk native vlan 10 |-----| trunk native vlan 20 |---->| trunk native vlan 30 |-----| access vlan 10 |----> 1.1.1.6
              |         port1        | SW1 |        port2         |     |        port1         | SW1 |     port2      |      
------------------------------------------------------------------------------------------------------------------------------------

Frame 2061: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

#arp request： untag数据包进入trunk native vlan 10 ，从trunk native vlan 20转发
Frame 2387: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: ARP (0x0806)
    Padding: 0000000000000000000000000000
    Trailer: 00000000
Address Resolution Protocol (request)

#arp request： vlan 10 数据包进入trunk native vlan 30，从access vlan 10出
Frame 1371: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)


# arp reply
------------------------------------------------------------------------------------------------------------------------------------
1.1.1.6 ----> | access vlan 10 |-----| trunk native vlan 30 |---->| trunk native vlan 20 |-----| access vlan 10 |----> 1.1.1.4
              |     port1      | SW1 |        port2         |     |        port1         | SW1 |     port2      |      
------------------------------------------------------------------------------------------------------------------------------------
                                tag 10                        tag 10                       tag 10            
Frame 1372: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Destination: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (reply)

Frame 2388: 64 bytes on wire (512 bits), 64 bytes captured (512 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Destination: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: ARP (0x0806)
    Padding: 0000000000000000000000000000
    Trailer: 00000000
Address Resolution Protocol (reply)

Frame 2062: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Destination: aa:bb:cc:00:04:11 (aa:bb:cc:00:04:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (reply)
# 


-------------------------------------------------------------------------------------------------------------
              |                    |     |                    |     |                    |  |     |
1.1.1.6 ----> |trunk native vlan 10|-SW1-|trunk native vlan 30|---->|trunk native vlan 20|--|trunk|----> 1.1.1.4
              |                    |     |                    |     |                    |  |     |
-------------------------------------------------------------------------------------------------------------

Frame 7406: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Destination: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.6, Dst: 1.1.1.3
Internet Control Message Protocol

Frame 8211: 118 bytes on wire (944 bits), 118 bytes captured (944 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Destination: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.6, Dst: 1.1.1.3
Internet Control Message Protocol

Frame 4608: 118 bytes on wire (944 bits), 118 bytes captured (944 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11), Dst: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Destination: aa:bb:cc:00:07:11 (aa:bb:cc:00:07:11)
    Source: aa:bb:cc:00:09:11 (aa:bb:cc:00:09:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.6, Dst: 1.1.1.3
Internet Control Message Protocol


1.1.1.3 ping 1.1.1.4 不通
request
-----------------------------------------------------------------------------------------
              |                               |     |                      |     
1.1.1.3 ----> |              trunk            | SW1 | trunk native vlan 10 |----> 1.1.1.4
              |              port1            |     |        port2         |   
-----------------------------------------------------------------------------------------
Frame 307: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

Frame 13: 68 bytes on wire (544 bits), 68 bytes captured (544 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:21 (aa:bb:cc:00:04:21), Dst: PVST+ (01:00:0c:cc:cc:cd)
    Destination: PVST+ (01:00:0c:cc:cc:cd)
    Source: aa:bb:cc:00:04:21 (aa:bb:cc:00:04:21)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 1
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 0001 = ID: 1
    Length: 50
Logical-Link Control
Spanning Tree Protocol
# trunk收，untag加pvid；trunk发,tag直接转发

1.1.1.4 ping 1.1.1.3 不通
request
--------------------------------------------------------------------------------------------------
              |                               |     |                               |     
1.1.1.4 ----> |      trunk native vlan 10     | SW1 |            trunk              |----> 1.1.1.3
              |             port2             |     |             port1             |   
--------------------------------------------------------------------------------------------------
Frame 6945: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11), Dst: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Destination: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Source: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.4, Dst: 1.1.1.3
Internet Control Message Protocol

Frame 3877: 118 bytes on wire (944 bits), 118 bytes captured (944 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11), Dst: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Destination: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Source: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.4, Dst: 1.1.1.3
Internet Control Message Protocol
# trunk收,untag加pvid；trunk发，tag直接转发

1.1.1.3 ping 1.1.1.4 通
request
--------------------------------------------------------------------------------------------------
              |                               |     |                               |     
1.1.1.3 ----> |         access vlan 10        | SW1 |      trunk native vlan 10     |----> 1.1.1.4
              |             port1             |     |             port2             |   
--------------------------------------------------------------------------------------------------
Frame 1777: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)

Frame 1786: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
    Destination: Broadcast (ff:ff:ff:ff:ff:ff)
    Source: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (request)
# trunk发，tag去pvid


reply
---------------------------------------------------------------------------------------------------
              |                               |     |                                |     
1.1.1.4 ----> |      trunk native vlan 10     | SW1 |          access vlan 10        |----> 1.1.1.3
              |             port2             |     |             port1              |   
---------------------------------------------------------------------------------------------------

Frame 2413: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11), Dst: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Destination: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Source: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (reply)

Frame 1980: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11), Dst: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Destination: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Source: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Type: ARP (0x0806)
    Padding: 000000000000000000000000000000000000
Address Resolution Protocol (reply)
# trunk收，untag加pvid


request 1.1.1.3 Ping 1.1.1.4 不通
--------------------------------------------------------------------------------------------------
              |                               |     |                               |     
1.1.1.3 ----> |         access vlan 10        | SW1 |      trunk native vlan 20     |----> 1.1.1.4
              |             port1             |     |             port2             |   
--------------------------------------------------------------------------------------------------
Frame 2563: 114 bytes on wire (912 bits), 114 bytes captured (912 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11), Dst: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Destination: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Source: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.3, Dst: 1.1.1.4
Internet Control Message Protocol

Frame 4152: 118 bytes on wire (944 bits), 118 bytes captured (944 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11), Dst: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Destination: aa:bb:cc:00:06:11 (aa:bb:cc:00:06:11)
    Source: aa:bb:cc:00:08:11 (aa:bb:cc:00:08:11)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 10
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1010 = ID: 10
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 1.1.1.3, Dst: 1.1.1.4
Internet Control Message Protocol
# trunk发，tag 直接转发

# DTP（DynamicTrunking protocol）是思科私有协议为Trunk服务，前身是DISL。可让交换机间的链路自动协商是否造成Trunk。
# TRUNK介绍过配置Trunk用switchporttrunk encapsulation dot1Q和switchportmode trunk这两条命令便可。
# 如今能够不用手动打这两条命令，而是用DTP来自动协商造成Trunk。另外DTP还能够协商Trunk链路的封装类型（802.1Q或ISL）。配置了DTP的交换机会发送DTP协商包，对方对DTP协商包进行响应，最终决定是否能够造成Trunk。
# 30s发送一次DTP的frame. 该协议仅在交换机间协商。

# DTP有4种模式类型是：auto，dersirable，trunk negotiate，trunk nonegotiate
# auto：被动协商，不主动发送DTP，但收到DTP后能够回复，回复后成功协商成Trunk链路
# desirable：指望把接口置于Trunk模式，会主动发送或回复DTP协商，只要对方能响应，就成功协商成Trunk链路
# negotiate：已经强制将端口配成Trunk模式了，会主动发送或回复DTP协商，只要对方能响应，就成功协商成Trunk链路
# nonegotiate：已经强制将端口配成Trunk模式了，但不主动发送或回复DTP协商。所以只有在对方端口已是negotiate或nonegotiate，即对方端口已经配置成了Trunk的状况下，才能造成Trunk链路

# 思科交换机端口的主干模式
# OFF(关闭)：使用"switchport mode access"命令，静态配置交换机端口为接入端口（非主干端口）。
# ON（打开）：使用"switchport mode trunk"命令，静态配置交换机端口为主干端口。
# Dynamic auto（动态自动）：使用"switchport mode dynamic auto"命令，静态配置交换机端口为动态自动模式。
# Dynamic desirable（动态指望）：使用"switchport mode dynamic desirable"命令，静态配置交换机端口为动态指望模式。
# Nonegotiate（关闭DTP协议）：使用"switchport nonegotiate"命令，将关闭DTP协议


--------------------------------------------------------------------
        |         SW1         |      |         SW2         | 
        |        trunk        |  --  |        trunk        |  
        |        none         |      |        none         |
--------------------------------------------------------------------      
                
IOU1(config)#do sh int e3/3 swi
Name: Et3/3
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: isl
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Appliance trust: none
IOU1(config)#

IOU2(config)#do sh int e3/3 swi
Name: Et3/3
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: isl
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Appliance trust: none
IOU2(config)#

Frame 5064: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33), Dst: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Destination: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)       # 目的MAC地址 CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc) 
    Source: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 1
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 0001 = ID: 1                                  # 802.1Q封装 vlan 1  
    Length: 34
    Padding: 0000000000000000
Logical-Link Control
    DSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = IG Bit: Individual
    SSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = CR Bit: Command
    Control field: U, func=UI (0x03)
        000. 00.. = Command: Unnumbered Information (0x00)
        .... ..11 = Frame type: Unnumbered frame (0x3)
    Organization Code: Cisco (0x00000c)                          # cisco 私有协议  
    PID: DTP (0x2004)                                            # 采用DTP协议
Dynamic Trunk Protocol:  (Operating/Administrative): Trunk/Desirable (0x83) (Operating/Administrative): ISL/Negotiated (0x40): aa:bb:cc:00:04:33
    Version: 1
    Domain
        Type: Domain (0x0001)
        Length: 5
        Domain: 
    Trunk Status
        Type: Trunk Status (0x0002)
        Length: 5
        Value: Trunk/Desirable (0x83)                            # Trunk Status ：Trunk/Desirable 模式
            1... .... = Trunk Operating Status: Trunk (0x1)
            .... .011 = Trunk Administrative Status: Desirable (0x3)
    Trunk Type
        Type: Trunk Type (0x0003)
        Length: 5
        Value: ISL/Negotiated (0x40)                             
            010. .... = Trunk Operating Type: ISL (0x2)                # trunk 类型为 ISL
            .... .000 = Trunk Administrative Type: Negotiated (0x0)    # 管理配置类型：Negotiated
    Sender ID
        Type: Sender ID (0x0004)
        Length: 10
        Sender ID: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33)
        
Frame 5065: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33), Dst: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Destination: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)        # 目的MAC地址 CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Source: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 1
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 0001 = ID: 1
    Length: 34
    Padding: 0000000000000000
Logical-Link Control
    DSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = IG Bit: Individual
    SSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = CR Bit: Command
    Control field: U, func=UI (0x03)
        000. 00.. = Command: Unnumbered Information (0x00)
        .... ..11 = Frame type: Unnumbered frame (0x3)
    Organization Code: Cisco (0x00000c)
    PID: DTP (0x2004)
Dynamic Trunk Protocol:  (Operating/Administrative): Trunk/Desirable (0x83) (Operating/Administrative): ISL/Negotiated (0x40): aa:bb:cc:00:06:33
    Version: 1
    Domain
        Type: Domain (0x0001)
        Length: 5
        Domain: 
    Trunk Status
        Type: Trunk Status (0x0002)
        Length: 5
        Value: Trunk/Desirable (0x83)
            1... .... = Trunk Operating Status: Trunk (0x1)
            .... .011 = Trunk Administrative Status: Desirable (0x3)
    Trunk Type
        Type: Trunk Type (0x0003)
        Length: 5
        Value: ISL/Negotiated (0x40)
            010. .... = Trunk Operating Type: ISL (0x2)
            .... .000 = Trunk Administrative Type: Negotiated (0x0)
    Sender ID
        Type: Sender ID (0x0004)
        Length: 10
        Sender ID: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33)
        
        
--------------------------------------------------------------------------------------------------
        |                 SW1                 |      |                 SW2                 | 
        |                trunk                |  --  |                trunk                | 
        |switchport trunk encapsulation dot1q |      |switchport trunk encapsulation dot1q |
        |       switchport mode trunk         |      |       switchport mode trunk         | 
--------------------------------------------------------------------------------------------------

IOU1(config-if)#do sh int e3/3 swi
Name: Et3/3
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Appliance trust: none
IOU1(config-if)#

IOU2(config-if)#do sh int e3/3 swi
Name: Et3/3
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Appliance trust: none
IOU2(config-if)#

Frame 6159: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33), Dst: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Destination: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Source: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 1
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 0001 = ID: 1
    Length: 34
    Padding: 0000000000000000
Logical-Link Control
    DSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = IG Bit: Individual
    SSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = CR Bit: Command
    Control field: U, func=UI (0x03)
        000. 00.. = Command: Unnumbered Information (0x00)
        .... ..11 = Frame type: Unnumbered frame (0x3)
    Organization Code: Cisco (0x00000c)
    PID: DTP (0x2004)
Dynamic Trunk Protocol:  (Operating/Administrative): Trunk/On (0x81) (Operating/Administrative): 802.1Q/802.1Q (0xa5): aa:bb:cc:00:06:33
    Version: 1
    Domain
        Type: Domain (0x0001)
        Length: 5
        Domain: 
    Trunk Status
        Type: Trunk Status (0x0002)
        Length: 5
        Value: Trunk/On (0x81)
            1... .... = Trunk Operating Status: Trunk (0x1)              # 
            .... .001 = Trunk Administrative Status: On (0x1)
    Trunk Type
        Type: Trunk Type (0x0003)
        Length: 5
        Value: 802.1Q/802.1Q (0xa5)
            101. .... = Trunk Operating Type: 802.1Q (0x5)               # Trunk Type : 802.1Q 
            .... .101 = Trunk Administrative Type: 802.1Q (0x5)          # 管理配置类型: 802.1Q         
    Sender ID
        Type: Sender ID (0x0004)
        Length: 10
        Sender ID: aa:bb:cc:00:06:33 (aa:bb:cc:00:06:33)
        
Frame 6160: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33), Dst: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Destination: CDP/VTP/DTP/PAgP/UDLD (01:00:0c:cc:cc:cc)
    Source: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, CFI: 0, ID: 1
    000. .... .... .... = Priority: Best Effort (default) (0)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 0001 = ID: 1
    Length: 34
    Padding: 0000000000000000
Logical-Link Control
    DSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = IG Bit: Individual
    SSAP: SNAP (0xaa)
        1010 101. = SAP: SNAP
        .... ...0 = CR Bit: Command
    Control field: U, func=UI (0x03)
        000. 00.. = Command: Unnumbered Information (0x00)
        .... ..11 = Frame type: Unnumbered frame (0x3)
    Organization Code: Cisco (0x00000c)
    PID: DTP (0x2004)
Dynamic Trunk Protocol:  (Operating/Administrative): Trunk/On (0x81) (Operating/Administrative): 802.1Q/802.1Q (0xa5): aa:bb:cc:00:04:33
    Version: 1
    Domain
        Type: Domain (0x0001)
        Length: 5
        Domain: 
    Trunk Status
        Type: Trunk Status (0x0002)
        Length: 5
        Value: Trunk/On (0x81)
            1... .... = Trunk Operating Status: Trunk (0x1)
            .... .001 = Trunk Administrative Status: On (0x1)
    Trunk Type
        Type: Trunk Type (0x0003)
        Length: 5
        Value: 802.1Q/802.1Q (0xa5)
            101. .... = Trunk Operating Type: 802.1Q (0x5)
            .... .101 = Trunk Administrative Type: 802.1Q (0x5)
    Sender ID
        Type: Sender ID (0x0004)
        Length: 10
        Sender ID: aa:bb:cc:00:04:33 (aa:bb:cc:00:04:33)