配置 DTP动态中继协议
配置 DTP动态中继协议
(Dynamic Trunking Protocol)，思科技术。
动态中继协议DTP，是 VLAN 组中思科的私有协议，主要用于协商两台设备间链路上的中继过程及中继封装 802.1Q 类型。DTP的用途是取代动态ISL（Dynamic ISL，DISL）。
下列是DTP可以配置的几种不同的状态：
* Access：使某个接口无条件进入Access模式，无DTP功能。
* Trunk：使某个接口无条件进入trunk模式并进行trunk链路协商，无论其邻居接口处于何种模式。
* Nonegotiate：指定DTP协商报文不允许在二层接口上发送。非协商状态，使接口成为永久的中继接口。由于接口不使用DTP信息帧进行通信，因此不会有协商发生。如果与非交换机设备相连的交换机接口存在DTP问题，那么在使用trunk之后可以使用nonegotiate，使得接口可以继续中继，但不会发送任何DTP信息。
* Dynamic desirable：使某个接口既主动发送DTP报文，也允许对DTP报文进行响应，这是以太网接口的默认状态。如果邻居接口是中继接口，并且被设置为on，desirable或auto，那么希望desirable状态下的这个接口成为中继接口。
* Dynamic auto：使某个接口可以响应DTP报文，但不允许主动发送DTP报文。只有在相邻接口要求该接口成为中继接口时才会成为中继接口。这是所有交换机接口的默认配置。auto接口不会主动要求对方，如果两个接口都被配置成auto状态，那么这两个接口都不会成为中继端。
* On：无论对端配置如何，该接口始终为中继接口。使用on状态时，必须指明帧的标记方式，因为此状态下接口不与对端进行协商。
* Off：该拉口永远是非中继接口。 第一个问题是，中继电缆（trunk cable）两端最好都能理解它们是中继端口，否则它们将中继帧视为正常帧。终端工作站无法理解信息帧头里另外添加的标签信息，其驱动程序栈也无法识别该标签信息，从而导致终端系统锁定或当机。为解决这个问题，思科推出了用于交换机的协议以实现通信目的。推出的第一版本是 VTP，即 VLAN 中继协议，它与 ISL 共同工作。最新推出的版本，即动态中继协议 （DTP），也可与 802.1q 共同工作。
其次是创建 LAN 。一个交换机的配置 VLAN ，需要做很多工作并且容易引起较多矛盾，如在一台交换机上 VLAN 100 属于工程部，而在另一台交换机上 VLAN100 可能被配置成属于财务部。这就使在故障排除工作中引起混乱，也会破坏精心设计的 VLAN 安全模式。该问题可通过 VTP/DTP 解决。在某台交换机上创建或删除一个 VLAN ，该信息自动传播到相同管理控制区域下的所有交换机上，这些交换机就是一个 VTP 域。
配置实验拓扑：
预备知识：
DTP (Dynamic Trunking Protocol), 用来动态协商端口类型为Access或者Trunk。要完成自动协商，2端口必须在同一个VTP domain中。每30s发送一次DTP的frame. 该协议仅在交换机间协商。
实验要求：
两台3560交换机用两条线相连，配置DTP协议，查看接口类型。
实验过程：
第一步：配置交换机3560-1与3560-2预配置
Switch>
Switch>en
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#hos 3560-1
3560-1(config)#no ip domain-loo
3560-1(config)#line con 0
3560-1(config-line)#no exec-t
3560-1(config-line)#logg syn
3560-1(config-line)#end
3560-1#
%SYS-5-CONFIG_I: Configured from console by console
3560-1#sh ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/1 unassigned YES manual up up
FastEthernet0/2 unassigned YES manual up up
FastEthernet0/3 unassigned YES manual down down
FastEthernet0/4 unassigned YES manual down down
FastEthernet0/5 unassigned YES manual down down
FastEthernet0/6 unassigned YES manual down down
3560-1#sh spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000A.4119.3495
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 000A.4119.3495
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p
Switch>
Switch>en
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#hos 3560-2
3560-2(config)#no ip domain-loo
3560-2(config)#line con 0
3560-2(config-line)#no exec-t
3560-2(config-line)#logg syn
3560-2(config-line)#end
3560-2#
%SYS-5-CONFIG_I: Configured from console by console
3560-2#sh ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/1 unassigned YES manual up up
FastEthernet0/2 unassigned YES manual up up
FastEthernet0/3 unassigned YES manual down down
FastEthernet0/4 unassigned YES manual down down
FastEthernet0/5 unassigned YES manual down down
3560-2#sh spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 000A.4119.3495
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 00D0.D396.CC29
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p //由于生成树自动打开，fa0/2阻塞
第二步：配置DTP动态协议
3560-1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
3560-1(config)#int fa 0/1
3560-1(config-if)#sw mode ?
access Set trunking mode to ACCESS unconditionally
dynamic Set trunking mode to dynamically negotiate access or trunk mode
trunk Set trunking mode to TRUNK unconditionally
3560-1(config-if)#sw mode dy
3560-1(config-if)#sw mode dynamic ?
auto Set trunking mode dynamic negotiation parameter to AUTO
desirable Set trunking mode dynamic negotiation parameter to DESIRABLE
3560-1(config-if)#sw mode dynamic de
3560-1(config-if)#sw mode dynamic desirable
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
3560-1(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
3560-1(config-if)#no sh
3560-1(config-if)#exi
3560-1(config)#int fa 0/2
3560-1(config-if)#sw mode dy
3560-1(config-if)#sw mode dynamic de
3560-1(config-if)#sw mode dynamic desirable
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up
3560-1(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up
3560-1(config-if)#no sh
3560-1(config-if)#end //3560-1 DTP协议配置完
3560-2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
3560-2(config)#int fa 0/1
3560-2(config-if)#sw mode dy de
3560-2(config-if)#sw mode dy desirable
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
3560-2(config-if)#
3560-2(config-if)#no sh
3560-2(config-if)#int fa 0/2
3560-2(config-if)#sw mode dy de
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up
3560-2(config-if)#
3560-2(config-if)#no sh
第三步：DTP检验
3560-1#sh int sw
Name: Fa0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
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)
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 encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: All
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Name: Fa0/2
Switchport: Enabled
Administrative Mode: dynamic desirable
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)
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 encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: All
--More--
3560-1#sh int tru
Port Mode Encapsulation Status Native vlan
Fa0/1 auto n-802.1q trunking 1
Fa0/2 auto n-802.1q trunking 1 //可以看出协商成功
Port Vlans allowed on trunk
Fa0/1 1-1005
Fa0/2 1-1005
Port Vlans allowed and active in management domain
Fa0/1 1
Fa0/2 1
Port Vlans in spanning tree forwarding state and not pruned
Fa0/1 1
Fa0/2 1