CDP Layer Same VLAN ?

Daughterofrnbsoul

Does CDP Work even if 2 switches are interconnected with each other Via Access Port, but are on Separate VLANS ?


SW1 Fa0/1 VLan 20

---

SW2 Fa0/3VLAN 30


Can sw1 still get the Ip address and everything else from show CDP Neighbors Detail regardless of VLAN ?

clarson

with cdp version 2, which you should be running, one of the pieces of information that is exchange between interfaces is the vlan id. So, when the vlans are different you should be getting a vlan mismatch error message.

Daughterofrnbsoul

clarson wrote: »

with cdp version 2, which you should be running, one of the pieces of information that is exchange between interfaces is the vlan id. So, when the vlans are different you should be getting a vlan mismatch error message.

I'm using packet tracer , but I have 2950 switches, but I don't see version 2

rob42

I'm sure that someone will correct me if I'm wrong, but my understanding is that CDP packets are not passed through a switch, so you will only see what is directly connected.

To map out the network, use show cdp neighbor, note down directly connected neighbors, then use show
cdp neighbors detail and note the IP addresses. You can then SSH or Telnet into the next device and run the CDP commands again to see what's again directly connected, and so on, until you've mapped out the network.

Using the example on Page 274 of the W. Odom ICND1 100-101 Book...



... if you were at PC1 (or PC2), to know about R1, you'd need to first Telnet to SW1, run the CDP commands and then Telnet from SW1 to SW2, then run the CDP commands again.

The next thing I'm going to do is to expand this topology to include VLANs so that I can see what the CDP output will look like from each device.

CDP Version-2 (CDPv2) is the most recent release of the protocol and provides more intelligent device tracking features.

A good learning question. Thank you.

DCD

It at the bottom of the output.

Sw1#sh cdp neighbors detail

Device ID: Sw3
Entry address(es):
IP address : 10.1.30.1
Platform: cisco 2950, Capabilities: Switch
Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/3
Holdtime: 175


Version :
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA4, RELEASE SOFTWARE(fc1)
Copyright (c) 1986-2005 by cisco Systems, Inc.
Compiled Wed 18-May-05 22:31 by jharirba


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Daughterofrnbsoul

yes I saw after further examination in my lab haha X_X