CDP is showing the wrong information.

[chandra_rc16]

Hi All,

I'm practicing for my CCNA. Now i'm analysing the CDP.

My topology has a router and 2 switches as shows below.

Here i configured the Fa0/2 ports on both switches to be half-duplex. But the "show cdp entry *" is showing that the port is operating in an full duplex mode.

Here is the confirmation that i configured fa0/2 on both switches as half-duplex:

Truncated output from switch0:

switch0#show interfaces fastEthernet 0/2

FastEthernet0/2 is up, line protocol is up (connected)

  Hardware is Lance, address is 00d0.ba12.5102 (bia 00d0.ba12.5102)

BW 100000 Kbit, DLY 1000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Half-duplex, 100Mb/s

  input flow-control is off, output flow-control is off

Truncated output from switch1:

switch1#show interfaces fastEthernet 0/2

FastEthernet0/2 is up, line protocol is up (connected)

  Hardware is Lance, address is 00e0.8f36.6502 (bia 00e0.8f36.6502)

BW 100000 Kbit, DLY 1000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Half-duplex, 100Mb/s

  input flow-control is off, output flow-control is off

Here is the output from switch0 for "show cdp entry *" command:

Truncated o/p:

switch0#show cdp entry *

Device ID: switch1

Entry address(es):

  IP address : 10.11.12.253

Platform: cisco 2960, Capabilities: Switch

Interface: FastEthernet0/2, Port ID (outgoing port): FastEthernet0/2

Holdtime: 144

Version :

Cisco IOS Software, C2960 Software (C2960-LANBASE-M), Version 12.2(25)FX, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2005 by Cisco Systems, Inc.

Compiled Wed 12-Oct-05 22:05 by pt_team

advertisement version: 2

Duplex: full                         //whereas it has to be half //

---------------------------

Thanks in advance for help.

Regards,

Chandu

[Leo Laohoo · Accepted solution]

Chandu,

That's one of the biggest problems with simulators when it comes to discrepancies.

[chandra_rc16]

Thanks Leo.

But can you let me know whose duplex settings will "show cdp entry * " command shows.

Here in this case will it shows the duplex setting of switch0's interface or switch1's interface ?

Regards,

Chandu

[Leo Laohoo · Accepted solution]

In real switches, "sh cdp neighbor" will give you good details better than simulators.  Even old switches like 2900XL/3500XL are very good studying tools for your certification.  You can get working 2900XL/3500XL cheaply from e-bay.

[chandra_rc16]

Will there be any question regarding CDP in the ccna exam ?

[Leo Laohoo]

Will there be any question regarding CDP in the ccna exam ?

Depends on your "luck".  You will get any random questions from the Cisco database.

[chandra_rc16]

Finally, will i pass CCNA with PT ?

Because i cannot offer a real equipment.

Regards,

Chandu

[johnlloyd_13]

Hi,

Yes, you can pass CCNA R/S with PT. There's already a version 6 released which includes ISR G2 routers running IOS 15.0.

I would stay away from "XL" switches as they're limited with commands that it supports.

Sent from Cisco Technical Support iPhone App

[chandra_rc16]

Thanks for you feedback.

Regards,

Chandu