配置 Catalyst 交换机之间的 802.1Q 中继

简介

本文档介绍运行Cisco IOS®软件的Cisco Catalyst交换机之间的IEEE 802.1Q (dot1q)中继的区别。

先决条件

要求

尝试进行此配置之前，请确保满足以下要求：

• 了解 IEEE 802.1Q 中继

• 使用命令行界面(CLI)配置Catalyst 3560和Catalyst 6500系列交换机的知识

使用的组件

本文档中的信息基于以下软件和硬件版本：

• 运行 Cisco IOS 软件版本 12.2(25)SEA 的 Catalyst 3560 交换机

• 运行 Cisco IOS 软件版本 12.1(26)E1 的 Catalyst 6509 交换机

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您的网络处于活动状态，请确保您了解所有命令的潜在影响。

背景信息

本文档提供了运行Cisco IOS^®软件的Cisco Catalyst 3560交换机与Catalyst 6500系列交换机之间的IEEE 802.1Q (dot1q)中继的示例配置。中继是一种在两个设备之间点到点链路上传输来自若干 VLAN 的流量的方式。

在传统平台上，有两种实施以太网中继的方法：

1. 交换机间链路协议 (ISL) - Cisco 专有协议

2. 802.1Q - IEEE标准

Catalyst组件

本文档中的Catalyst 3560和6500配置也适用于运行Cisco IOS软件的其他Catalyst交换机。

注意：请参阅以下文档以了解各种Catalyst交换机所支持的中继方法：

• 在Catalyst交换机上实施中继的系统要求

注意：本文档仅包含交换机的配置文件和相关示例 show   命令的输出。有关如何在Catalyst交换机之间配置802.1Q TRUNK的详细信息，请参阅以下文档：

• 配置 VLAN 的配置 VLAN 中继部分 - Catalyst 3560 系列交换机

• 配置第2层以太网接口的了解VLAN中继部分-运行Cisco IOS软件的Catalyst 4500系列交换机

背景理论

IEEE 802.1Q 使用内部标记机制。中继设备先插入 4 字节标记来识别帧所属的 VLAN，再重新计算帧校验序列 (FCS)。有关详细信息，请参阅以下文档：

• 交换机间链路和 IEEE 802.1Q 帧格式

注意：下面是此配置要记住的重要说明：

• Catalyst 3560/3750系列交换机上的任何以太网接口都可以支持802.1Q和ISL封装。默认情况下，Catalyst 3550 交换机上的以太网接口是第 2 层 (L2) 端口。

• Catalyst 6500/6000 系列交换机上的所有以太网端口均可支持 802.1Q 和 ISL 封装。

• 默认情况下，运行 Cisco IOS 软件的 Catalyst 4500 系列交换机支持 ISL 和 802.1Q 中继模式。这在 WS-X4418-GB 和 WS-X4412-2GB-T 模块上阻塞千兆端口以外的所有接口上均受到支持。这些端口不支持 ISL 而只支持 802.1Q 中继。端口 3 至 18 是 WS-X4418-GB 模块上的阻塞千兆端口。端口 1 至 12 是 WS-X4412-2GB-T 模块上的阻塞千兆端口。

注意：如果端口与背板的连接超订用，则该端口为阻塞端口。

• Catalyst 6500和Catalyst 4500平台之间的主要区别在于默认接口配置。默认情况下，运行Cisco IOS软件的Catalyst 6500交换机的接口处于关闭模式，即第3层(L3)路由端口。运行Cisco IOS软件的Catalyst 4500交换机启用了所有的接口。默认情况下，接口是 L2 交换机端口。

• 当802.1Q封装用于Catalyst 3750交换机上的中继接口时，可在 show interface 输出中看到残帧，因为61-64字节的有效802.1Q封装数据包（包括q标记）被Catalyst 3750交换机算作是过小帧，即使这些数据包被正确地转发。

注意：请注意，运行Cisco IOS XE的最新Catalyst交换机（例如3650/3850和更高版本）不再支持ISL协议。

配置

本部分提供有关如何配置本文档所述功能的信息。

网络图

本文档使用以下网络设置：

注意：Catalyst 3560上的千兆以太网接口是10/100/1000 Mbps协商以太网接口。因此，在此网络图中，Catalyst 3560 上的千兆端口连接到 Catalyst 6500 上的快速以太网 (100 Mbps) 端口。

网络图

配置

本文档使用以下配置：

• Catalyst 3560 交换机

• Catalyst 6500 交换机

!--- Notice: This example creates VLAN 1 and VLAN 2 
!--- and sets the VLAN Trunk Protocol (VTP) mode to transparent. Use your 
!--- network as a basis and set the VTP mode accordingly. For more details, 
!--- refer to Configuring VLANs.


 version 12.2 
 no service pad 
 service timestamps debug uptime 
 service timestamps log uptime 
 no service password-encryption 
 ! 
 hostname 3560 
 ! 

!--- This is the privileged mode password for the example.

 enable password mysecret
 ! 
 ip subnet-zero  
 ! 
 vtp mode transparent
 ! 

!--- VLAN 2 is created. This is visible only when you set VTP mode 
!--- to transparent. 

 vlan 2
 !


!--- The Gigabit Ethernet interface on the Catalyst 3560 is a 10/100/1000 Mbps 
!--- negotiated Ethernet interface. Therefore, the Gigabit port on the 
!--- Catalyst 3560 is connected to a Fast Ethernet port on the Catalyst 6500. 
!--- Configure the trunk on the Gigabit Ethernet 0/1 interface.

 interface GigabitEthernet0/1 

!--- Configure trunk encapsulation as dot1q. 
!--- For details on trunking, refer to Configuring VLANs.

  switchport trunk encapsulation dot1q 

!--- Enable trunking on the interface.

  switchport mode trunk 
  no ip address 
  snmp trap link-status 
 !
 !

!--- Interfaces Gigabit Ethernet 0/2 through 0/5 are placed in VLAN 1. 
!--- In order to configure the interface as an L2 port, 
!--- refer to the Configuring Ethernet Interfaces section 
!--- of Configuring Interface Characteristics. All L2 ports are placed 
!--- in VLAN 1, by default.

 interface GigabitEthernet0/2 
  switchport mode access
  no ip address 
  snmp trap link-status 
 ! 
 interface GigabitEthernet0/3
  switchport mode access
  no ip address 
  snmp trap link-status 
 !
 !
 interface GigabitEthernet0/4 
  switchport mode access 
  no ip address 
  snmp trap link-status 
 ! 
 interface GigabitEthernet0/5 
  switchport mode access 
  no ip address 
  snmp trap link-status 
 ! 
 !

!--- Interfaces Gigabit Ethernet 0/6 through 0/12 are placed in VLAN 2.

 interface GigabitEthernet0/6 
 switchport access vlan 2 
 switchport mode access
 no ip address 
 snmp trap link-status 
 ! 
 
!--- Output suppressed.

 ! 
 interface GigabitEthernet0/12 
  switchport access vlan 2 
  switchport mode access 
  no ip address 
  snmp trap link-status 
 ! 
 interface Vlan1

!--- This is the IP address for management.

 ip address 10.1.1.1 255.255.255.0 
 ! 
 ip classless 
 ip http server 
 ! 
 ! 
 line con 0 
 transport input none 
 line vty 0 4 

!--- This is the privileged mode password for the example.

 password mysecret
 login 
 line vty 5 15 
 login 
 ! 
 end

!--- Notice: This example creates VLAN 1 and VLAN 2 and sets 
!--- the VTP mode to transparent. Use your network as a basis and set the VTP 
!--- mode accordingly. For more details, refer to Configuring VLANs.


 Current configuration : 4812 bytes
 version 12.1 
 service timestamps debug uptime 
 service timestamps log uptime 
 no service password-encryption 
 ! 
 hostname Cat6500 
 ! 
 vtp mode transparent
 ip subnet-zero
 !
 !
 mls flow ip destination 
 mls flow ipx destination 
 !

!--- This is the privileged mode password for the example.

 enable password mysecret
 ! 
 redundancy 
 mode rpr-plus
 main-cpu 
 auto-sync running-config
 auto-sync standard 
 ! 
 ! 

!--- This enables VLAN 2.

 vlan 2
 !
 interface GigabitEthernet1/1 
  no ip address 
  shutdown 
 ! 
 interface GigabitEthernet1/2 
  no ip address 
  shutdown 
 ! 

!--- The Gigabit Ethernet interface on the Catalyst 3560 is a 10/100/1000 Mbps 
!--- negotiated Ethernet interface. Therefore, the Gigabit port on the Catalyst 3560 
!--- is connected to a Fast Ethernet port on the Catalyst 6500.

 interface FastEthernet3/1 
  no ip address 

!--- You must issue the switchport command once, 
!--- without any keywords, in order to configure the interface as an L2 port for the 
!--- Catalyst 6500 series switch that runs Cisco IOS Software. 
!--- On a Catalyst 4500 series switch that runs Cisco IOS Software, all ports are L2 
!--- ports by default. Therefore, if you do not change the default configuration, 
!--- you do not need to issue the switchport command.


  switchport 

!--- Configure trunk encapsulation as dot1q. 
!--- For more details on trunking, refer to 
!--- Configuring LAN Ports for Layer 2 Switching for the Catalyst 6500 series switch 
!--- that runs Cisco IOS Software, or  Configuring Layer 2 Ethernet Interfaces 
!--- for the Catalyst 4500/4000 series switch that runs Cisco IOS Software.

  switchport trunk encapsulation dot1q 


!--- Enable trunking on the interface.


  switchport mode trunk 
 ! 

!--- Configure interfaces Fast Ethernet 3/2 through 3/24 to be in access mode. 
!--- By default, all access ports are configured in VLAN 1. 

 interface FastEthernet3/2
  no ip address
  switchport
  switchport mode access
 ! 
 

!--- Output suppressed.

 !
 interface FastEthernet3/24
  no ip address 
  switchport 
  switchport mode access
 !

!--- Fast Ethernet 3/25 through 3/48 are placed in VLAN 2. 


 interface FastEthernet3/25
  no ip address 
  switchport 
  switchport access vlan 2 
  switchport mode access 
 ! 
  

!--- Output suppressed.

 ! 
 interface FastEthernet3/48
  no ip address 
  switchport 
  switchport access vlan 2 
  switchport mode access 
 ! 
 ! 
 interface Vlan1 

!--- This is the IP address for management.

  ip address 10.1.1.2 255.255.255.0 
 ! 
 !
 ip classless 
 no ip http server 
 ! 
 ! 
 ip classless
 ip http server
 ! 
 line con 0 
 exec-timeout 0 0 
 transport input none 
 line vty 0 4 

!--- This is the Telnet password for the example.

 password mysecret
 login 
 
 ! 
 end 

注意：如果将接口分配给不存在的VLAN，该接口将关闭，直到您在VLAN数据库中创建VLAN。有关详细信息，请参阅配置 VLAN 的创建或修改以太网 VLAN 部分。

验证

使用本部分可确认配置能否正常运行。在 Catalyst 3560/3750/6500/4500 交换机上，请使用以下命令：

• show interfaces <interface_type module/port> trunk

• show interfaces <interface_type module/port> switchport

• show vlan

• show vtp status

  show

命令输出示例

Catalyst 3560 交换机

• show interfaces <interface_type module/por> trunk —此命令显示接口的中继配置以及能够通过中继为其传输流量的VLAN编号。

  3560#show interface gigabitethernet 0/1 trunk
   
  Port      Mode         Encapsulation  Status        Native vlan
  Gi0/1     on           802.1q         trunking      1
   
  Port      Vlans allowed on trunk
  Gi0/1     1 4094
   
  Port      Vlans allowed and active in management domain
  Gi0/1     1-2
   
  Port      Vlans in spanning tree forwarding state and not pruned
  Gi0/1     1-2

• show interfaces <interface_type module/port> switchport —此命令显示接口的交换机端口配置。

  在显示器中，选中 Operational Mode 和 Operational Trunking Encapsulation 字段。

  3560#show interface gigabitethernet 0/1 switchport
  Name: Gi0/1
  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)
  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 

• show vlan - 此命令提供有关 VLAN 及属于特定 VLAN 的端口的信息。

  3560#show vlan
   
  VLAN Name                             Status    Ports
  ---- -------------------------------- --------- -------------------------------
  1    default                          active    Gi0/2, Gi0/3, Gi0/4, Gi0/5
  2    VLAN0002                         active    Gi0/6, Gi0/7, Gi0/8, Gi0/9
                                                              Gi0/10, Gi0/11, Gi0/12
  
  1002 fddi-default                     act/unsup
  1003 token-ring-default               act/unsup
  1004 fddinet-default                  act/unsup
  1005 trnet-default                    act/unsup
  
  !--- Output suppressed.
  
  

  注意：输出中显示的端口仅为接入端口。但是，配置为中继以及未连接状态的端口也显示在show vlan输出中。

• show vtp status - 此命令显示有关 VTP 管理域、状态和计数器的一般信息。

  3560#show vtp status
  VTP Version : 2 
  Configuration Revision : 0 
  Maximum VLANs supported locally : 1005 
  Number of existing VLANs : 6 
  VTP Operating Mode : Transparent      
  VTP Domain Name : 
  VTP Pruning Mode : Disabled 
  VTP V2 Mode : Disabled 
  VTP Traps Generation : Disabled 
  MD5 digest : 0x4A 0x55 0x17 0x84 0xDB 0x99 0x3F 0xD1 
  Configuration last modified by 10.1.1.1 at 0-0-00 00:00:00
  
  3560#ping 10.1.1.2 
  Type escape sequence to abort. 
  Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds: 
  !!!!! 
  Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms 
  3560#

Catalyst 6500 交换机

• show interfaces <interface_type module/port> trunk- 此命令显示接口的中继配置以及能够通过中继为其传输流量的VLAN编号。

Cat6500#show interfaces fastethernet 3/1 trunk
 
Port      Mode         Encapsulation  Status        Native vlan
Fa3/1     on           802.1q         trunking      1
 
Port      Vlans allowed on trunk
Fa3/1     1 4094
 
Port      Vlans allowed and active in management domain
Fa3/1     1-2
 
Port      Vlans in spanning tree forwarding state and not pruned
Fa3/1     1-2

• show interfaces <interface_type module/port> switchport —此命令显示接口的交换机端口配置。 在显示器中，选中 Operational Mode 和 Operational Trunking Encapsulation 字段。  

cat6500#show interface fastethernet 3/1 switchport 
Name: Fa3/1
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)
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

• show vlan - 此命令提供有关 VLAN 及属于特定 VLAN 的端口的信息。

Cat6500#show vlan
 
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa3/2, Fa3/3, Fa3/4, Fa3/5
                                                Fa3/6, Fa3/7, Fa3/8, Fa3/9
                                                Fa3/10, Fa3/11, Fa3/12, Fa3/13
                                                Fa3/14, Fa3/15, Fa3/16, Fa3/17
                                                Fa3/18, Fa3/19, Fa3/20, Fa3/21
                                                Fa3/22, Fa3/23, Fa3/24
2    VLAN0002                         active    Fa3/25, Fa3/26, Fa3/27, Fa3/28
                                                Fa3/29, Fa3/30, Fa3/31, Fa3/32
                                                Fa3/33, Fa3/34, Fa3/35, Fa3/36
                                                Fa3/37, Fa3/38, Fa3/39, Fa3/40
                                                Fa3/41, Fa3/42, Fa3/43, Fa3/44
                                                Fa3/45, Fa3/46, Fa3/47, Fa3/48
1002 fddi-default                      act/unsup
1003 token-ring-default                act/unsup
1004 fddinet-default                   act/unsup
1005 trnet-default                     act/unsup

注意：显示的端口仅限于那些已配置为第2层非中继（接入）端口的端口。配置为中继以及未连接状态的端口也显示在show vlan输出中。有关详细信息，请参阅配置用于第2层交换的LAN端口的“配置用于第2层交换的LAN接口”部分。

• show vtp status - 此命令显示有关 VTP 管理域、状态和计数器的一般信息。

  Cat6500#show vtp status
  VTP Version                     : 2
  Configuration Revision          : 0
  Maximum VLANs supported locally : 1005
  Number of existing VLANs        : 6
  VTP Operating Mode              : Transparent
  VTP Domain Name                 :
  VTP Pruning Mode                : Disabled
  VTP V2 Mode                     : Disabled
  VTP Traps Generation            : Disabled
  MD5 digest                      : 0xBF 0x86 0x94 0x45 0xFC 0xDF 0xB5 0x70
  Configuration last modified by 10.1.1.2 at 0-0-00 00:00:00

• ping

  Cat6500#ping 10.1.1.1
   
  Type escape sequence to abort.
  Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
  !!!!!
  Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

相关信息

• Catalyst 3560 系列交换机配置指南
• Catalyst 4500 系列交换机配置指南
• Catalyst 6500 系列交换机配置指南
• 思科技术支持和下载