Whitebox switching.

I recently sat my CCNP 300-115 – Switch exam. I spent months taking notes on all of the important information needed to pass the exam. This study guide focuses on all things related to CDP and LLDP.

Please see other CCNP Switch Sudy Guides


  • CDP uses TLV to advertise the native vlan
  • CDP is supported on frame relay sub interfaces
  • Link Layer Discovery Protocol – vendor neutral protocol
  • CDP version 2 provides enhanced reporting options
  • To activate CDP – Globally – cdp run Interface – cdp enable
  • LLDP-MED – is an extension to LLDP that operates between endpoint devices and network devices
  • CDP messages contain information on Native VLAN Ids, Port duplex, hardware platform.
  • LLDP cannot provide information about VTP
  • Default interval in which cdp sends advertisements – 60 seconds
  • CDP enabled by default – disabled by the no cdp run command globally
  • LLDP – mandatory TLVs – System capability TLV, System name TLV
  • CDP version 2 carries native vlan information.  CDP v1 doesn’t
  • LLDP global state disabled and interface state enabled
  • LLDP time <secs> – command to set the interval for LLDP
  • LLDP – frame has destination MAC address, frame has CRC
  • CDP – feature carries information about the voice vlan to a Cisco phone
  • LLDP is disabled globally by default, the LLDP interface state is disabled
  • TLVs that are mandatory in an LLDP message – Port ID and Chassis ID
  • 6 optional TLVs- Port description, System name, System description, System capabilities, Management address, Specific TLVs
  • 4 mandatory TLVs – end of LDPDU, Chasis id, port id, time to live
  • 2 organisationally specific TLV – Port vlan id tlv, MAC/ PHY configuration / status tlv
  • 2 advantages of LLDP over CDP – supports topology change notification, supports vendor agnostic
  • Command  that can cause LLDP to accept LLDP packets but not send – no LLDP transmit
  • Switches can run LLDP and CDP simultaneously
  • Devices with LLDP configured send advertisements messages to a multicast address on a periodic basis
  • CDP default interval – 60 seconds
  • LLDP – standards based protocol
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