Solved: CDP

ahmedsalahomar · ‎02-24-2010

As I know the main objective for CDP message is existence notes, but I have a question for that.

Does the CDP message could conatins information about VLANs in a switch?

I ask this question because I was work with an Optiview in a network discovery, I noticed that the device discovered the Network VLANs (SNMP is not configured), as I know we need to configure SNMP to get VLANs, but this didn't happen.

If CDP message not contains VLANs, any body have any explanation How Fluke Optiview get the information about VLANs?

Ganesh Hariharan · ‎02-25-2010

As I know the main objective for CDP message is existence notes, but I have a question for that.

Does the CDP message could conatins information about VLANs in a switch?

I ask this question because I was work with an Optiview in a network discovery, I noticed that the device discovered the Network VLANs (SNMP is not configured), as I know we need to configure SNMP to get VLANs, but this didn't happen.

If CDP message not contains VLANs, any body have any explanation How Fluke Optiview get the information about VLANs?

Hi,

CDP is a media- and protocol-independent protocol that runs on all Cisco-manufactured equipment including routers, bridges, access and communication servers, and switches. Using CDP, you can view information about all the Cisco devices directly attached to the switch. In addition, CDP detects native VLAN and port duplex mismatches.

CDP runs on all media that support Subnetwork Access Protocol (SNAP). CDP runs over the data link layer only.

Network management applications can retrieve the device type and SNMP-agent address of neighboringCisco devices using CDP. This allows applications to send SNMP queries to neighboring devices. CDP allows network management applications to discover Cisco devices that are neighbors of already known devices, in particular, neighbors running lower-layer, transparent protocols.

Hope to Help

Ganesh.H

View solution in original post

Giuseppe Larosa · ‎02-25-2010

Hello Ahmed,

CDP messages provide information about the native vlan of a port.

for example CDP can detect a vlan mismatch between two switch ports configured as access ports (switchport mode access).

To see this from IOS CLI you can use sh cdp neigh detail

example:

sh cdp n g1/14 det
-------------------------
Device ID: SW-TO-CRN-P2-VOICE
Entry address(es):
IP address: 10.84.48.43
Platform: cisco WS-C3560G-48PS, Capabilities: Switch IGMP
Interface: GigabitEthernet1/14, Port ID (outgoing port): GigabitEthernet0/52
Holdtime : 87 sec

Version :
Cisco IOS Software, C3560 Software (C3560-IPBASE-M), Version 12.2(25)SEB4, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Tue 30-Aug-05 14:19 by yenanh

advertisement version: 2
Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27, value=00000000FFFFFFFF010221FF000000000000001647A22000FF0000
VTP Management Domain: 'cernaia'
>>> Native VLAN: 100
Duplex: full
Management address(es):
IP address: 10.84.48.43

as you see the native vlan is reported if the port were an access port the field would provide the vlan to which the port is associated

Hope to help

Giuseppe

Ganesh Hariharan · ‎02-25-2010

As I know the main objective for CDP message is existence notes, but I have a question for that.

Does the CDP message could conatins information about VLANs in a switch?

I ask this question because I was work with an Optiview in a network discovery, I noticed that the device discovered the Network VLANs (SNMP is not configured), as I know we need to configure SNMP to get VLANs, but this didn't happen.

If CDP message not contains VLANs, any body have any explanation How Fluke Optiview get the information about VLANs?

Hi,

CDP is a media- and protocol-independent protocol that runs on all Cisco-manufactured equipment including routers, bridges, access and communication servers, and switches. Using CDP, you can view information about all the Cisco devices directly attached to the switch. In addition, CDP detects native VLAN and port duplex mismatches.

CDP runs on all media that support Subnetwork Access Protocol (SNAP). CDP runs over the data link layer only.

Network management applications can retrieve the device type and SNMP-agent address of neighboringCisco devices using CDP. This allows applications to send SNMP queries to neighboring devices. CDP allows network management applications to discover Cisco devices that are neighbors of already known devices, in particular, neighbors running lower-layer, transparent protocols.

Hope to Help

Ganesh.H