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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
2、包括加密与解密、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
3、和集线器对广播帧是透明的，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 Protoco
4、l Data 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
5、桥每个端口都是指定端口。(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
6、听状态：listening 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
7、认VLAN是VLAN1，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,
8、their VLAN membership remains the same.,VLAN Configuration Modes,Global Mode,Switch#configure terminal Switch(config)#vlan 3 Switch(config-vlan)#name Vlan3Switch(config-vlan)#exit Switch(config)#end,VLAN Configuration Modes,Database Mode,Switch#vlan database Switch(vlan)#vlan 3 VLAN 3 added:Name:VLA
9、N0003Switch(vlan)#exit APPLY completed.Exiting.,VLAN Access Ports,The access switch port associated with a single data VLAN,VLAN Implementation Commands,Configuring VLANsvlan 101switchport mode accessswitchport access vlan 101Verifying VLANsshow interfacesshow vlan,Configuring an Access VLAN,Switch(
10、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 Access VLAN Config
11、uration,Switch#show vlanVLAN Name Status Ports-1 default active Fa0/1,Fa0/2,Fa0/3,Fa0/4 Fa0/5,Fa0/7,Fa0/911 asw11_data active12 asw12_data active95 VLAN0095 active Fa0/899 Trunk_Native active100 Internal_Access active111 voice-for-group-11 active112 voice-for-group-12 active1002 fddi-default act/uns
12、up1003 token-ring-default act/unsup1004 fddinet-default act/unsup1005 trnet-default act/unsupVLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1-1 enet 100001 1500-0 enet 100011 1500-0.,Defining VLANs,Implementing Trunks,Maintaining Specific VLAN Identification,Specifically developed for m
13、ulti-VLAN interswitch communicationsPlaces a unique identifier in each frameFunctions at Layer 2,VLAN Trunking,Comparing ISL and 802.1Q,Trunking with ISL,Is a Cisco proprietary 专利protocolSupports PVSTUses an encapsulation process Does not modify the original frame,ISL Encapsulation,Trunking with 802
14、.1Q,An IEEE standardAdds a 4-byte tag to the original frameAdditional tag includes a priority field Does not tag frames that belong to the native VLANSupports Cisco IP telephony,The 802.1Q Tagging Process,802.1Q Native VLAN,Native VLAN frames are carried over the trunk link untagged.,VLAN Ranges,Tru
15、nking Configuration Commands,Configuring a Trunkswitchport trunkswitchport modeswitchport nonegotiate,Trunks can be configured statically or via DTP.DTP provides the ability to negotiate the trunking method.,Switchport Mode Interactions,Note:Table assumes DTP is enabled at both ends.,show dtp interf
16、ace 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 Layer 2 trunk.Specify the trunking native VLAN(for 802.1Q).Configure the allowable VLANs for this trunk.Use the no sh
17、utdown 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)#shutdown Switch(config-if)#switchport trunk encapsulation dot1q Switch(config-if)#switchport trunk allowed vlan 1,5,
18、11,1002-1005 Switch(config-if)#switchport mode trunkSwitch(config-if)#switchport trunk native vlan 99Switch(config-if)#switchport nonegotiate Switch(config-if)#no shutdown,Verifying the 802.1Q Configuration,Switch#show running-config interface fastethernet|gigabitethernet slot/port,Switch#show inter
19、faces fastethernet|gigabitethernet slot/port switchport|trunk,Switch#show interfaces fastEthernet 5/8 switchportName:fa5/8Switchport:EnabledAdministrative Mode:trunkOperational Mode:trunkAdministrative Trunking Encapsulation:dot1qOperational Trunking Encapsulation:dot1qNegotiation of Trunking:OffAcc
20、ess 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 802.1Q Dynamic Trunk Link,Switch#show running-config interface fastethernet 5/8 Building configuration.Current configuration:!interface FastEthernet5/8 sw
21、itchport mode dynamic desirable switchport trunk encapsulation dot1q Switch#show interfaces fastethernet 5/8 trunk Port Mode Encapsulation Status Native vlanFa5/8 desirable 802.1q trunking 99 Port Vlans allowed on trunkFa5/8 1,5,11,1002-1005 Port Vlans allowed and active in management domainFa5/8 1,
22、5,1002-1005 Port Vlans in spanning tree forwarding state and not prunedFa5/8 1,5,1002-1005,ISL Trunk Configuration,Switch(config)#interface fastethernet 2/1 Switch(config-if)#shutdown Switch(config-if)#switchport trunk encapsulation isl Switch(config-if)#switchport trunk allowed vlan 1-5,1002-1005Sw
23、itch(config-if)#switchport mode trunkSwitch(config-if)#switchport nonegotiateSwitch(config-if)#no shutdown,Verifying ISL Trunking,Switch#show running-config interface fastethernet|gigabitethernet slot/port,Switch#show interfaces fastethernet|gigabitethernet slot/port switchport|trunk,Switch#show int
24、erfaces fastethernet 2/1 trunk Port Mode Encapsulation Status Native VLAN Fa2/1 trunk isl trunking 99 Port VLANs allowed on trunk Fa2/1 1-5,1002-1005 Port VLANs allowed and active in management domain Fa2/1 1-2,1002-1005 Port VLANs in spanning tree forwarding state and not pruned Fa2/1 1-2,1002-1005
25、,Summary,Trunk links carry traffic from multiple VLANs.ISL is Cisco proprietary and encapsulates the Layer 2 frames.802.1Q is an IEEE standard 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 comm
26、ands are used to configure and verify ISL and 802.1Q trunk links.Allow only required VLANs over the trunk.,Defining VLANs,Propagating VLAN Configurations with VTP,The VTP Domain,Group of switches that exchange VLAN information VLANs administered centrally at a chosen switch,The VTP Protocol,Advertis
27、es VLAN configuration informationMaintains VLAN configuration consistency throughout a common administrative domainSends advertisements on trunk ports only,VTP Modes,ClientCannot create,change,or delete VLANs Forwards advertisementsSynchronizes VLAN configurationsDoes not save in NVRAM,TransparentCr
28、eates,modifies,and deletes local VLANsForwards advertisementsDoes not synchronize VLAN configurationsSaves configuration in NVRAM,Server(default mode)Creates,modifies,and deletes VLANsSends and forwards advertisementsSynchronizes VLAN configurationsSaves configuration in NVRAM,Pruning Disabled,Pruni
29、ng Enabled,VTP Pruning,Uses bandwidth more efficiently by reducing unnecessary flooded trafficExample:Station A sends 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 synch
30、ronized to the latest revision number.VTP advertisements are sent every 5 minutes or when there is a change.,VTP Configuration Commands,Configuring VTPvtp domainvtp modevtp passwordVerifying VTPshow vtp statusshow vtp counters,Configuring a VTP Management Domain,Configure each switch in the followin
31、g order to avoid dynamic learning of the domain name:VTP passwordVTP domain name(case sensitive)VTP mode(server mode is the default),Configuring and Verifying VTP,Verifying the VTP Configuration,Switch#show vtp status VTP Version:2Configuration Revision:28Maximum VLANs supported locally:1005Number o
32、f existing VLANs:17VTP Operating Mode:ClientVTP Domain Name:BCMSNVTP Pruning Mode:EnabledVTP V2 Mode:DisabledVTP Traps Generation:DisabledMD5 digest:0 x45 0 x52 0 xB6 0 xFD 0 x63 0 xC8 0 x49 0 x80Configuration last modified by 10.1.1.1 at 8-12-05 15:04:49Switch#,Switch#show vtp status,Verifying the
33、VTP Configuration(Cont.),Switch#show vtp countersVTP statistics:Summary advertisements received:7Subset advertisements received:5Request advertisements received:0Summary advertisements transmitted:997Subset advertisements transmitted:13Request advertisements transmitted:3Number of config revision er
34、rors:0Number of config digest errors:0Number of V1 summary errors:0 VTP pruning statistics:Trunk Join Transmitted Join Received Summary advts received from non-pruning-capable device-Fa5/8 43071 42766 5,Switch#show vtp counters,Implementing Inter-VLAN Routing,Describing Routing Between VLANs,Inter-V
35、LAN Routing with External Router,Single trunk link carries traffic for multiple VLANs to and from router.,Inter-VLAN Routing External Router Configuration Commands,Configure on subinterfaceencapsulation dot1Q(or isl)10Verifyshow vlan 10show ip route,Inter-VLAN Routing on External Router:802.1Q Trunk
36、 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,
