Cisco Discovery Protocol (CDP) is primarily used to obtain protocol addresses of neighboring devices and discover the platform of those devices. CDP can also be used to show information about the interfaces your router uses. CDP is media- and protocol-independent, and runs on all Cisco-manufactured equipment including routers, bridges, access servers, and switches.
CDP runs on all media that support Subnetwork Access Protocol (SNAP), including local-area network (LAN), Frame Relay, and Asynchronous Transfer Mode (ATM) physical media. CDP runs over the data link layer only. Therefore, two systems that support different network-layer protocols can learn about each other.
Each device configured for CDP sends periodic messages, known as advertisements, to a multicast address. Each device advertises at least one address at which it can receive SNMP messages. The advertisements also contain time-to-live, or holdtime, information, which indicates the length of time a receiving device should hold CDP information before discarding it. Each device also listens to the periodic CDP messages sent by others in order to learn about neighboring devices and determine when their interfaces to the media go up or down.
CDP is a Cisco proprietary Layer 2 protocol that is media- and protocol-independent, and runs on all Cisco-manufactured equipment that includes:
A Cisco device enabled with CDP sends out periodic interface updates to a multicast address in order to make itself known to neighbors. Since it is a layer two protocol, these packets (frames) are not routed. Use of SNMP with the CDP MIB allows network management applications to learn the device type and the SNMP agent address of neighboring devices, and to send SNMP queries to those devices.
Let us apply CDP on packet tracer.
In the above topology, we have different devices attached with each other. So, if we want to look for the information of neighboring devices, we will apply the following command on Router enabled mode, “show cdp neighbors”.
And on Router 2 and 3 as well, as shown in figures below.
It can be seen clearly that it gives us the information of the neighboring devices. Note one thing here, that it gives us the information of the routers and switches that are directly attached to its ports. However, it does not gives us information about the hosts that are attached to it directly.
Sticky MAC addresses are addresses that are dynamically learned once and remain stick to the port, we can adjust the max number of sticky MAC addresses to a single interface. the use of this feature is in large networks usually where we cant afford to waste time doing manual mac addresses to port mapping.
Let us apply this concept on packet tracer.
Let us set up a topology. Apply PCs with the IP addresses dynamically with the DHCP server set on the Server.
DHCP server setup on server.
Assigning IP to PCs.
Now, let us apply Sticky Mac address to the following interface of switch which is currently attach to PC1. It is interface fa 0/3.
The following commands will apply this concept.
Go to enable mode. Apply command, show running-config.
Now, we do not have MAC address of PC here.
For this, remove the interface from PC1 attach it to another PC as shown in the figure below.
Request for DHCP.
Now. we have mac address and our port is sticky as shown in figure below.
MAC address of PC.
Now, re connect to PC1 and request for IP address. It has failed and it has also shutdown the interface because MAC address does not match with the MAC address of the port.
Let us create wireless topology on packet tracer. For this go to the wireless devices and select linksys wireless router, take some PCs and provide them with wireless linksys module so that they can communicate through router wirelessly. For that go to the PC physical mode as shown in the figures below.
Go to PC, and remove wired LAN and install wireless LAN module.
Now, its removed. Let us add wireless module.
NOw, PCs are connected.
Set the IP address.
As this wireless router provides us with the DHCP service, so we can obtain IP automatically by using this service for our PCs.
So now our PCs can communicate.
Now, let us apply authentication to our wireless router. For that, go to Config tab, click on Wireless. Provide it with the information as described below.
Go to PC desktop mode, Click on PC Wireless.
Click on connect. Select the device, you want to connect to, click connect.
Give correct password.
Now, we are done with it. We have successfully applied authentication.
Now, let us use Access point to connect to PCs wirelessly.
We can also connect wired router to access point in order to make our router wireless.
Apply IP addresses and put the status on.
We can also give authentication key to Access Point as well.
In this tutorial we are going apply inter vlan routing. In order to communicate between different vlans, we use this phenomenon. Let us apply vlan on the following topology, then we will apply vtp (vlan trunking protocol).
Now, in order to communicate between different vlans we will have to create sub interfaces of fast ethernet interface of router. Let us do that. Note that, we will create as many sub interfaces as many vlans we are using in our topology. In this case we are using 2 vlans, so we will create two sub interfaces for both vlans.
We will also apply encapsulation of sub interface.
Let us create vlans and assign those vlans to switch interfaces i.e. PCs
In order to apply VTP we will have write the following commands. Apply the domain name, and trunk the ports of switch. Note, trunk only those ports that are connected to router and switches.
Thus, vlans are visible in other switches too after trunking.
Trunk the port of the switch 1 as well.
Now, we see ,in the bottom right corner, we are able to communicate in between vlans and that s what we wanted , isnt it ?
Let us apply ACL (Access Control List) on the topology. First, let us assign IP addresses and change the state of the interfaces.
Here, the status is change as shown in the following diagram.
Then, we will have to assign IP addresses to the PCs.
And the PC attach to the other interface. Please note the difference between default gateways. We assign fast Ethernet interface address to default gateway.
Thus, after applying IP addresses. We see that Packet transfer is successful.
Let us apply ACL and permit and deny Hosts IP’s as we want. We are going to deny and permit certain hosts as follows.
Let us apply ACL and permit and deny Hosts IP’s as we want.
Then, we will have to tell the interface that which ACL to follow. ACL is uniquely identified with the number, in this case 1.
Now, you see that the denied will not be able to send the data while those who we permit can send packet.
Similarly, in the bottom right corner you can see status.
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