white berry bold: cdp protocol emulator CDP - The Easy Tutorial

https://sourceforge.net/projects/cdp4win/?source=directory

WinPcap: Packet.dll -- Packet Driver API

http://openmaniak.com/cdp.php

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The CDP protocol:

The Cisco Discovery Protocol (CDP) is a proprietary layer 2 network protocol developed by Cisco Systems.
It runs on Cisco and some HP equipment devices.

It is useful for two reasons:

- -	Getting information about the directly connected CDP devices such as the operating system version and IP address. Checking that the OSI layer 2 connectivity is okay in case of IP (OSI layer 3) connectivity problems

The CDP announcements are sent to the multicast destination address 01-00-0c-cc-cc-cc.

CDP on Linux:

Linux does not natively support the CDP protocol, so we have to use a tool called "cdp-tools" to activate it.

Enabling CDP on Linux systems can be interesting on routers like Quagga and Vyatta in a Cisco environment.

Download CDP-tools in the /root directory.
If you want to download "cdp-tools" directly from the Linux CLI, proceed as follows:

#wget http://gpl.internetconnection.net/files/cdp-tools.tar.gz

Extract "cdp-tools":

#tar -xvf cdp-tools.tar

This will create the "cdp-tools" directory.

Download and install the "build-essential" meta-package containing the tools to compile programs.

#apt-get install build-essential

Download and install libnet0-dev:
Libnet0 is a generic networking API that provides access to several protocols.

#apt-get install libnet0-dev

The libpcap library (in our example libpcap0.8-dev) is installed at the same time.

Compile "cdp-tools":

#make

cc -D_BSD_SOURCE -D__BSD_SOURCE -D__FAVOR_BSD -DHAVE_NET_ETHERNET_H -DLIBNET_LIL_ENDIAN -c -o cdp-listen.o cdp-listen.c
cc cdp-listen.o /usr/lib/libpcap.so -o cdp-listen
cc -D_BSD_SOURCE -D__BSD_SOURCE -D__FAVOR_BSD -DHAVE_NET_ETHERNET_H -DLIBNET_LIL_ENDIAN -c -o cdp-send.o cdp-send.c
cdp-send.c:70: warning: 'packed’ attribute ignored for field of type ‘unsigned char[6]'
cdp-send.c:71: warning: 'packed' attribute ignored for field of type 'unsigned char[6]'
cdp-send.c:74: warning: 'packed' attribute ignored for field of type 'u_int8_t'
cdp-send.c:75: warning: 'packed' attribute ignored for field of type 'u_int8_t'
cdp-send.c:77: warning: 'packed' attribute ignored for field of type 'u_int8_t'
cdp-send.c:78: warning: 'packed' attribute ignored for field of type 'u_int8_t[3]'
cc cdp-send.o /usr/lib/libnet.so -o cdp-send

If everything goes as planned, you should have two new files called "cdp-send" and "cdp-listen" which are used to respectively send or receive traffic.

1. cdp-send 2. cdp-listen

1. cdp-send

Launch cd-send

cdp-send is used to send CDP traffic to directly connected devices.

Let's launch cdp-send with the minimal setting:

Syntax: cdp-send [options] interfaces... &

/root/cdp-tools/cdp-send eth0

"eth0" is the interface through which we are sending CDP traffic.
"/root/cdp-tools/cdp-send eth1 eth2" would send CDP traffic trough the eth1 and eth2 interfaces.

Check how a directly connected Cisco device sees our Linux machine:

Cisco_device>show cdp neighbours

Capability Codes:	R - Router, T - Trans Bridge, B - Source Route Bridge
	S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID	Local Intrfce	Holdtme	Capability	Platform	Port ID
ubuntu	Fas 1/0/5	176	H	i686	eth0

The Linux system is seen as a layer 3 host "H", on interface "eth0", with a hostname "ubuntu" and a platform "i386".

Cisco_device>show cdp neighbours details

Device ID: ubuntu
Entry address(es):
IP address: 10.1.1.1
Platform: i686, Capabilities: Host
Interface: FastEthernet1/0/5, Port ID (outgoing port): eth0
Holdtime : 120 sec

Version :
Linux 2.6.22-10-generic

advertisement version: 2
Management address(es):

Configure "cdp-tools" to start automatically on startup:

#crontab -u root -e

@reboot /root/cdp-send eth0