1、OSI七层协议,OSI(Open System interconnection)开放系统互连参考模型1、物理层 数据单位是位(BIT)，典型设备是集线器HUB。2、链路层 数据单位是帧，实现对MAC地址的访问，典型设备是交换机Switch。3、网络层 数据单位是包，使用的是IP地址，典型设备是路由器Router。4、传输层 提供端到端的服务。可以实现流量控制、负载均衡。传输层信息包含 端口、控制字和校验和。传输层协议主要是TCP和UDP。5、会话层 主要内容是通过会话进行身份验证、会话管理和确定通讯方式6、表示层 主要是解释通讯数据的意义，如代码转换、格式变换等，使不同的终端可以表示。还包括加
2、密与解密、压缩与解压缩等。7、应用层 应用层应该是直接面向用户的程序或服务，包括系统程序和用户程序，例如www、FTP、DNS、POP3和SMTP等都是应用层服务。,数据包封装与解封装,数据在发送时是数据从应用层至物理层的一个打包的过程接收时是数据从物理层至应用层的一个解包的过程,交换机,交换机是根据网桥的原理发展起来的，学习交换机先认识两个概念：(1)冲突域：冲突域是数据必然发送到的区域。HUB是无智能的信号驱动器，有入必出，整个由HUB组成的网络是一个冲突域。交换机的一个接口下的网络是一个冲突域，所以交换机可以隔离冲突域。(2)广播域：广播数据时可以发送到的区域是一个广播域。交换机和集线器
3、对广播帧是透明的，所以用交换机和HUB组成的网络是一个广播域。路由器的一个接口下的网络是一个广播域。所以路由器可以隔离广播域。,STP,交换网络中的环以太网是总线或星型结构，不能构成环路，否则会产两个严重后果：(1)产生广播风暴，造成网络堵塞。(2)克隆帧会在各个口出现，造成地址学习(记录帧源地址)混乱。解决环路问题方案:(1)网络在设计时，人为的避免产生环路。(2)使用生成树STP(Spanning Tree Protocol)功能，将有环的网络剪成无环网络。STP被IEEE802规范为802.1d标准。,生成树协议术语(1)网桥协议数据单元：BPDU(Bridge Protocol Dat
4、a Unit)BPDU是生成树协议交换机间通讯的数据单元，用于确定角色。(2)网桥号：Bridge ID交换机的标识号，它由优先级和MAC地址组成，优先级16位，MAC地址48位。(3)根网桥：Root bridge根网桥定义为网桥号最小的交换机，根网桥所有的端口都不会阻塞。(4)根端口：Root port非根网桥到根网桥累计路径花费最小的端口，负责本网桥与根网桥通讯的接口。(5)指定网桥：Designated bridge网络中到根网桥累计路径花费最小交换机，负责收发本网段数据。(6)指定端口：Designated port网络中到根网桥累计路径花费最小的交换机端口，根网桥每个端口都是指定端
5、口。(7)非指定端口：NonDesignated port余下的端口是非指定端口，它们不参与数据的转发，也就是被阻塞的端口。(根端口是从非根网桥选出，指定端口是网段中选出)。,STP,生成树协议的状态：生成树协议工作时，所有端口都要经过一个端口状态的建立过程。生成树协议通过BPDU广播，确定各交换机及其端口的工作状态和角色，交换机上的端口状态分别为：关闭、阻塞、侦听、学习和转发状态。(1)关闭状态：Disabled 不收发任何报文，当接口空连接或人为关闭时处于关闭状态。(2)阻塞状态：Blocking 在机器刚启动时，端口是阻塞状态(20秒)，但接收BPDU信息。(3)侦听状态：listeni
6、ng 不接收用户数据(15秒)，收发BPDU，确定网桥及接口角色。(4)学习状态：learning 不接收用户数据(15秒)，收发BPDU，进行地址学习。(5)转发状态：Forwarding 开始收发用户数据，继续收发BPDU和地址学习,维护STP。,VLAN,VLAN(Virtual Lan)是虚拟逻辑网络交换机通过VLAN设置，可以划分为多个逻辑网络，从而 隔离广播域。具有三层模块的交换机可以实现VLAN间的路由。,VLAN,(1)端口模式交换机端口有两种模式，access和trunk。access口用于与计算机相连，而交换机之间的连接，应该是trunk。交换机端口默认VLAN是VLAN1
7、，工作在access模式。具有相同VLAN号的端口在同一个广播域中。Trunk又称为干线，可以设置允许多个VLAN通过。(2)VLAN中继协议：VLAN中继协议有两种：ISL(Inter-Switch Link)： ISL是Cisco专用的VLAN中继协议。802.1q(dot1q)：802.1q是标准化的，应用较为普遍。,What Is an End-to-End VLAN?,Users are grouped into VLANs independent of physical location. If users are moved within the campus, their VL
8、AN membership remains the same.,VLAN Configuration Modes,Global Mode,Switch# configure terminal Switch(config)# vlan 3 Switch(config-vlan)# name Vlan3 Switch(config-vlan)# exit Switch(config)# end,VLAN Configuration Modes,Database Mode,Switch# vlan database Switch(vlan)# vlan 3 VLAN 3 added:Name: VL
9、AN0003 Switch(vlan)# exit APPLY completed. Exiting,VLAN Access Ports,The access switch port associated with a single data VLAN,VLAN Implementation Commands,Configuring VLANs vlan 101 switchport mode access switchport access vlan 101 Verifying VLANs show interfaces show vlan,Configuring an Access VLA
10、N,Switch(config)# vlan vlan_id,Create a VLAN.,Switch(config-vlan)# name vlan_name,Provide a VLAN name.,Switch(config-if)# switchport mode access,Place the switch port into access mode.,Switch(config-if)# switchport access vlan vlan_id,Associate the access switch port with a VLAN.,Verifying the Acces
11、s VLAN Configuration,Switch#show vlanVLAN Name Status Ports - - - - 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4Fa0/5, Fa0/7, Fa0/9 11 asw11_data active 12 asw12_data active 95 VLAN0095 active Fa0/8 99 Trunk_Native active 100 Internal_Access active 111 voice-for-group-11 active 112 voice-for-group-12
12、 active 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsupVLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 - - - - - - - - - 1 enet 100001 1500 - - - - - 0 enet 100011 1500 - - - - - 0 . . . . . . . . . . . .,Definin
13、g VLANs,Implementing Trunks,Maintaining Specific VLAN Identification,Specifically developed for multi-VLAN interswitch communications Places a unique identifier in each frame Functions at Layer 2,VLAN Trunking,Comparing ISL and 802.1Q,Trunking with ISL,Is a Cisco proprietary 专利protocol Supports PVST
14、 Uses an encapsulation process Does not modify the original frame,ISL Encapsulation,Trunking with 802.1Q,An IEEE standard Adds a 4-byte tag to the original frame Additional tag includes a priority field Does not tag frames that belong to the native VLAN Supports Cisco IP telephony,The 802.1Q Tagging
15、 Process,802.1Q Native VLAN,Native VLAN frames are carried over the trunk link untagged.,VLAN Ranges,Trunking Configuration Commands,Configuring a Trunk switchport trunk switchport mode switchport nonegotiate,Trunks can be configured statically or via DTP. DTP provides the ability to negotiate the t
16、runking method.,Switchport Mode Interactions,Note: Table assumes DTP is enabled at both ends.,show dtp interface to determine current setting,How to Configure Trunking,Enter interface configuration mode. Shut down interface. Select the encapsulation (802.1Q or ISL). Configure the interface as a Laye
17、r 2 trunk. Specify the trunking native VLAN (for 802.1Q). Configure the allowable VLANs for this trunk. Use the no shutdown command on the interface to activate the trunking process. Verify the trunk configuration.,802.1Q Trunk Configuration,Switch(config)#interface fastethernet 5/8 Switch(config-if
18、)#shutdown Switch(config-if)#switchport trunk encapsulation dot1q Switch(config-if)#switchport trunk allowed vlan 1,5,11,1002-1005 Switch(config-if)#switchport mode trunk Switch(config-if)#switchport trunk native vlan 99 Switch(config-if)#switchport nonegotiate Switch(config-if)#no shutdown,Verifyin
19、g the 802.1Q Configuration,Switch#show running-config interface fastethernet | gigabitethernet slot/port,Switch#show interfaces fastethernet | gigabitethernet slot/port switchport | trunk ,Switch#show interfaces fastEthernet 5/8 switchport Name: fa5/8 Switchport: Enabled Administrative Mode: trunk O
20、perational Mode: trunk Administrative Trunking Encapsulation: dot1q Operational Trunking Encapsulation: dot1q Negotiation of Trunking: Off Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 99 (trunk_only) Trunking VLANs Enabled: 1,5,11,1002-1005 Pruning VLANs Enabled: 2-1001. . .,Verifying a
21、802.1Q Dynamic Trunk Link,Switch#show running-config interface fastethernet 5/8 Building configuration. Current configuration: ! interface FastEthernet5/8switchport mode dynamic desirableswitchport trunk encapsulation dot1qSwitch#show interfaces fastethernet 5/8 trunk Port Mode Encapsulation Status
22、Native vlan Fa5/8 desirable 802.1q trunking 99Port Vlans allowed on trunk Fa5/8 1,5,11,1002-1005Port Vlans allowed and active in management domain Fa5/8 1,5,1002-1005Port Vlans in spanning tree forwarding state and not pruned Fa5/8 1,5,1002-1005,ISL Trunk Configuration,Switch(config)#interface faste
23、thernet 2/1 Switch(config-if)#shutdown Switch(config-if)#switchport trunk encapsulation isl Switch(config-if)#switchport trunk allowed vlan 1-5,1002-1005 Switch(config-if)#switchport mode trunk Switch(config-if)#switchport nonegotiate Switch(config-if)#no shutdown,Verifying ISL Trunking,Switch#show
24、running-config interface fastethernet | gigabitethernet slot/port,Switch#show interfaces fastethernet | gigabitethernet slot/port switchport | trunk ,Switch#show interfaces fastethernet 2/1 trunk Port Mode Encapsulation Status Native VLANFa2/1 trunk isl trunking 99Port VLANs allowed on trunkFa2/1 1-
25、5,1002-1005Port VLANs allowed and active in management domainFa2/1 1-2,1002-1005Port VLANs in spanning tree forwarding state and not prunedFa2/1 1-2,1002-1005,Summary,Trunk links carry traffic from multiple VLANs. ISL is Cisco proprietary and encapsulates the Layer 2 frames. 802.1Q is an IEEE standa
26、rd for trunking, which implements a 4-byte tag. The 802.1Q native VLANs forward frames without the tag. VLAN numbers have specific ranges and purposes. Various commands are used to configure and verify ISL and 802.1Q trunk links. Allow only required VLANs over the trunk.,Defining VLANs,Propagating V
27、LAN Configurations with VTP,The VTP Domain,Group of switches that exchange VLAN informationVLANs administered centrally at a chosen switch,The VTP Protocol,Advertises VLAN configuration information Maintains VLAN configuration consistency throughout a common administrative domain Sends advertisement
28、s on trunk ports only,VTP Modes,Client Cannot create, change, or delete VLANs Forwards advertisements Synchronizes VLAN configurations Does not save in NVRAM,Transparent Creates, modifies, and deletes local VLANs Forwards advertisements Does not synchronize VLAN configurations Saves configuration in
29、 NVRAM,Server (default mode) Creates, modifies, and deletes VLANs Sends and forwards advertisements Synchronizes VLAN configurations Saves configuration in NVRAM,Pruning Disabled,Pruning Enabled,VTP Pruning,Uses bandwidth more efficiently by reducing unnecessary flooded traffic Example: Station A se
30、nds broadcast; broadcast flooded only toward any switch with ports assigned to the red VLAN,VTP Operation,VTP advertisements are sent as multicast frames. VTP servers and clients are synchronized to the latest revision number. VTP advertisements are sent every 5 minutes or when there is a change.,VT
31、P Configuration Commands,Configuring VTP vtp domain vtp mode vtp passwordVerifying VTP show vtp status show vtp counters,Configuring a VTP Management Domain,Configure each switch in the following order to avoid dynamic learning of the domain name: VTP password VTP domain name (case sensitive) VTP mo
32、de (server mode is the default),Configuring and Verifying VTP,Verifying the VTP Configuration,Switch#show vtp status VTP Version : 2 Configuration Revision : 28 Maximum VLANs supported locally : 1005 Number of existing VLANs : 17 VTP Operating Mode : Client VTP Domain Name : BCMSN VTP Pruning Mode :
33、 Enabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x45 0x52 0xB6 0xFD 0x63 0xC8 0x49 0x80 Configuration last modified by 10.1.1.1 at 8-12-05 15:04:49 Switch#,Switch#show vtp status,Verifying the VTP Configuration (Cont.),Switch#show vtp countersVTP statistics: Summary adve
34、rtisements received : 7 Subset advertisements received : 5 Request advertisements received : 0 Summary advertisements transmitted : 997 Subset advertisements transmitted : 13 Request advertisements transmitted : 3 Number of config revision errors : 0 Number of config digest errors : 0 Number of V1 s
35、ummary errors : 0VTP pruning statistics: Trunk Join Transmitted Join Received Summary advts received fromnon-pruning-capable device - - - - Fa5/8 43071 42766 5,Switch#show vtp counters,Implementing Inter-VLAN Routing,Describing Routing Between VLANs,Inter-VLAN Routing with External Router,Single tru
36、nk link carries traffic for multiple VLANs to and from router.,Inter-VLAN Routing External Router Configuration Commands,Configure on subinterface encapsulation dot1Q (or isl) 10 ip address 10.10.1.1 255.255.255.0 Verify show vlan 10 show ip route,Inter-VLAN Routing on External Router: 802.1Q Trunk
37、Link,Inter-VLAN Routing on External Router: ISL Trunk Link,Verifying Inter-VLAN Routing,The ping command tests connectivity to remote hosts.,Verifying the Inter-VLAN Routing Configuration,Router#show ip interface brief,Displays the current IP configuration per VLAN,Router#show ip route,Displays IP route table information,Router#show vlan,Displays IP address on interfaces and current state of interface,
