Cisco switch port Mode

The port operating mode of a vswitch can be divided into three types: Access, Multi, and Trunk. In cisco networks, there are four main types of interfaces in the final stable state of switches in LAN: access, trunk, multi, dot1q-tunnel. 1. access: it is mainly used to access terminal devices, such as PCs, servers, and print servers. 2. tru

The port operating mode of a vswitch can be divided into three types: Access, Multi, and Trunk. In cisco networks, there are four main types of interfaces in the final stable state of switches in LAN: access, trunk, multi, dot1q-tunnel. 1. access: it is mainly used to access terminal devices, such as PCs, servers, and print servers. 2. tru

VswitchOfPortWorkModeGenerally, there are three types: Access, Multi, and Trunk.

In the cisco network,VswitchThere are four main types of interfaces in the final stable State in LAN: access, trunk, multi, dot1q-tunnel.

1. access: it is mainly used to access terminal devices, such as PCs, servers, and print servers.

2. trunk: Mainly used to connect to otherVswitchTo carry multiple VLANs on the route.

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Cisco supports multiple Trunk methods (I .e. VLAN frame identification ):

2.1. ISL-Cisco proprietary encapsulation protocol, which is also the default protocol. Add 26 bytes first and 4 bytes later. Frame Length: 1518/1548. The number of supported VLANs is 1-1046.

2.2. IEEE 802.1Q-IEEE standard method. VLAN information is written into the frame header, and only four bytes of FCS are added later.

The frame length is 1518/1522. It has a 12-bit vlan ID and supports up to 4096 VLANs.

802.1Q-trunk defines native VLAN (local VLAN) for forwarding untagged frames ).VswitchNativeVLAN can forward layer-2 frames on unlabeled trunks. The receiver forwards all unlabeled frames to the native VLAN. VLAN1 is the default local VLAN. You can also change another VLAN to a local VLAN. If ISL is used, the unencapsulated frame will be discarded, including nativeVLAN. All data will be encapsulated.

2.3-Cisco proprietary protocol for transmitting VLAN information on FDDI, which writes VLAN information into the SAID Security Association identifier Section

2.4. LANE-an IEEE Standard Method for transmitting VLAN information based on ATM.

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3. multi: It carries multiple VLANs in a single line, but unlike trunk, it does not label the bearer data. It is mainly used to access servers that support multiple VLANs or some network analysis devices. Currently, this type of interface is basically not used. It is basically not supported in cisco network devices.

4. dot1q-tunnel: Used in the Q-in-Q tunnel configuration.

Cisco network devices support dynamic negotiationPortIt provides some convenience for the implementation of network devices (but dynamic mode is not recommended ). The cisco dynamic negotiation protocol evolved from the initial DISL (Cisco private Protocol) to DTP (Public protocol ). According to the Implementation of Dynamic protocols, Cisco network device interfaces are divided into the following types:Mode:

1. switchport mode access: forces an interface to become an access interface, and can negotiate with the other party to induce the other party to become an access interface.Mode.

2. switchport mode dynamic desirable: It is possible to negotiate with the other party to become a Trunk interface. If the neighbor InterfaceModeIs one of the Trunk/desirable/auto, the interface will become the trunk interface. If the trunk cannot be formedModeIn the accessMode. ThisModeIs nowVswitchBy defaultMode.

3. switchport mode dynamic auto: only neighborsVswitchIt turns into a Trunk interface only when it actively negotiates with itself, so it is a passiveModeWhen the neighbor interface is Trunk/desirable, it will become Trunk. If the trunk cannot be formedModeIn the accessMode.

4. switchport mode trunk: forces the interface to become a Trunk interface, and actively induces the other party to become a TrunkMode, So when the neighborVswitchWhen the interface is trunk/desirable/auto, it will become a Trunk interface.

5. switchport nonegotiate: strictly speaking, this is not an interface.ModeIt only blocksVswitchInterface to send DTP data packets, that is, prohibitPortSend a negotiation packet to the other party. It must be used with switchport mode trunk or switchport mode access.

6, switchport mode dot1q-tunnel: ConfigurationVswitchThe interface is a tunnel interface (non-Trunk)VswitchThe Trunk interface of to form an asymmetric link.

InCisco4507VswitchView onPortOfMode

Cisco00007 (config-if) # switchport?

Access Set access mode characteristics of the interface

Block Disable forwarding of unknown uni/multi cast addresses

Host Set port host

Mode Set trunking mode of the interface

Nonegotiate Device will not engage in negotiation protocol on this

Interface

Port-security Security related command

Priority Set appliance 802.1 p priority

Private-vlan Set the private VLAN configuration

Trunk Set trunking characteristics of the interface

Voice Voice appliance attributes

Cisco3167 (config-if) # switchport mode access?

Cisco3167 (config-if) # switchport mode trunk?

Cisco00007 (config-if) # switchport mode?

Access Set trunking mode to ACCESS unconditionally

The dot1q-tunnel set trunking mode to TUNNEL unconditionally

Dynamic Set trunking mode to dynamically negotiate access or trunk mode

Private-vlan Set the mode to private-vlan host or promiscuous

Trunk Set trunking mode to TRUNK unconditionally

Cisco3167 (config-if) # switchport mode dynamic?

Auto Set trunking mode dynamic negotiation parameter to AUTO

Desirable Set trunking mode dynamic negotiation parameter to DESIRABLE

ConfigurationVswitchModeExample 1

SW1:

Interface FastEthernet0/1

Switchport mode dynamic desirable

View PortOf ModeAssume that the peer interface is configured as static access. ModeNegotiate as access, as shown below

SW1 # show interface fa0/1 switchport

Name: Fa0/1

Switchport: Enabled

Administrative Mode: dynamic desirable

Operational Mode: static access

Administrative Trunking Encapsulation: negotiate

Operational Trunking Encapsulation: native

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

If two connectedVswitchPortBoth are configured as switchport mode dynamic desirable. First, it is negotiated as trunk and encapsulated as ISL.

Configuration Example 2: (assume that f0/13 of SW1 is connected to F0/13 of SW2)

SW1 (f0/13) -------- (f0/13) SW2

SW1

Interface FastEthernet0/13

Switchport mode dynamic desirable

SW2

Interface FastEthernet0/13

Switchport mode dynamic desirable

SW1 # show interface status | include (Port | Fa0/13)

Port Name Status Vlan Duplex Speed Type

Fa0/13 connectedTrunkA-full a-100 10/100 BaseTX

Pay attention to the bold part, and the final negotiationModeIs trunk, and the encapsulated protocol is ISL

SW1 # show interface fa0/13 switchport

Name: Fa0/13

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)