cdp/dtp/pagp/vtp

CDP= Cisco Discovery Protocol

  • Encapsulation:              802.3 : 802.2 - SNAP HDLC
  • Protocol Type Code:     0x2000
  • Multicast Address:        01:00:0C:CC:CC:CC
  • Timer:                         60 sec
  • Holdtime:                    180 sec

DTP = Dynamic Trunking Protocol

  • Encapsulation:              802.3 : 802.2 - SNAP HDLC
  • Protocol Type Code:     0x2004
  • Multicast Address:        01:00:0C:CD:CD:CD
  • 802.1Q                        Sent on the Native Untagged VLAN
  • ISL                             Sent encapsulated as VLAN 1

DTP Modes, Combinations and Configuration Example

Access (Off)
         sw1 (config-if) switchport mode access

  • Puts the interface into permanent nontrunking mode and negotiates to convert the link into a nontrunking link. The interface becomes a nontrunk interface even if the neighboring interface does not change.

Dynamic Auto
         sw1 (config-if) switchport mode dynamic auto

  • Makes the interface convert the link to a trunking link if the neighboring interface is set to trunk or desirable mode. This is the default mode for all Ethernet interfaces.

Dynamic Desirable
         sw1 (config-if) switchport mode dynamic desireable

  • Makes the interface actively attempt to convert the link to a trunking link. The interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode.

Trunk
         sw1 (config-if) switchport mode trunk

  • Puts the interface into permanent trunking mode and negotiates to convert the link into a trunking link. The interface becomes a trunk interface even if the neighboring interface does not change.

Nonegotiate (Access)
         sw1(config-if) switchport nonegotiate
         sw1(config-if) switchport mode access

  • Puts the interface into permanent access mode but prevents the interface from generating DTP frames. You must configure the neighboring interface manually as a access interface to make sure you establish a usable access link.

Nonegotiate (Trunk)
         sw1(config-if) switchport nonegotiate
         sw1(config-if) switchport mode trunk

  • Puts the interface into permanent trunking mode but prevents the interface from generating DTP frames. You must configure the neighboring interface manually as a trunk interface to make sure you establish a usable trunking link.

DTP Modes

access
(off)

dynamic
auto

dynamic 
desirable

trunk
(on) 

nonegotiate
(access) 

nonegotiate
(trunk)

access
(off)

static
access

static
access

static
access

unexpected
results

static access

unexpected
results

dynamic
auto

static
access

static
access

trunk

trunk

static
access

unexpected
results

dynamic
desireable

trunk

trunk

trunk

trunk

static
access

unexpected
results

trunk
(on)

unexpected
results

trunk

trunk

trunk

unexpected
results

trunk

nonegotiate
(access)

static
access

static
access

static
access

unexpected
results

static
access

unexpected
results

nonegotiate
(trunk)

unexpected
results

unexpedted
results

unexpected
results

trunk

unexpected
results

trunk

PaGP = Port Aggragation Protocol

 

UDLD = Unidirectional Link Detection

  •  

VTP = VLAN Trunking Protocol

  • triggered update
  • every 5 minutes / 300 seconds

本文转自:http://www.ubernet.us/8.html

Mode
Description

on

Mode that forces the LAN port to channel unconditionally. In the on mode, a usable EtherChannel exists only when a LAN port group in the on mode is connected to another LAN port group in the on mode. Because ports configured in the on mode do not negotiate, there is no negotiation traffic between the ports. You cannot configure the on mode with an EtherChannel protocol. If one end uses the on mode, the other end must also.

auto

PAgP mode that places a LAN port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not initiate PAgP negotiation. (Default)

desirable

PAgP mode that places a LAN port into an active negotiating state, in which the port initiates negotiations with other LAN ports by sending PAgP packets.

passive

LACP mode that places a port into a passive negotiating state, in which the port responds to LACP packets it receives but does not initiate LACP negotiation. (Default)

active

LACP mode that places a port into an active negotiating state, in which the port initiates negotiations with other ports by sending LACP packets.

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