Cisco CCNA Making Your Router a TFTP Server
Now this is a great feature of a Cisco router! If you do not have a laptop or other host that can provide TFTP services, you can make a router a TFTP server with the global configuration command “tftp-server flash:”. You will then need to make sure the file (i.e. IOS image) is available on the router you configured as a tftp server. It is as simple as that, you can now copy the image from the router configured as a tftp server allowing upgrade or downgrade of your other router.
Cisco CCNA Dynamic Host Configuration Protocol
DHCP is used to assign IP addresses automatically and to set TCP/IP stack configuration parameters, such as the subnet mask, default router, and Domain Name System (DNS) servers. DHCP is also used to provide other configuration information as necessary, including the length of time the address has been allocated to the host. DHCP consists of two components: a protocol for delivering host-specific configuration parameters from a DHCP server to a host, and a mechanism for allocating network addresses to hosts.
Using DHCP, a host can obtain an IP address quickly and dynamically. All that is required is a defined range of IP addresses on a DHCP server. As hosts come online, they contact the DHCP server and request address information. The DHCP server selects an address and allocates it to that host. The address is only leased to the host, so the host will periodically contact the DHCP server to extend the lease. This lease mechanism ensures that hosts that have been moved or are switched off for extended periods of time do not hold on to addresses that they do not use. The addresses are returned to the address pool by the DHCP server, to be reallocated as necessary.
Cisco CCNA Making your Router a DHCP Server
This is another great Cisco router feature.
It is important that you understand that the router maps the pool to the interface which has an IP address in the same subnet as the pool.
In the example above, the Fa1/1 interface must be assigned the IP address 192.168.10.1 or the pool will not hand out IP addresses to clients.
Note: The IP address of 192.168.10.1 is excluded from the pool since it is assigned to the router. Additional addresses can be excluded if they are specifically assigned to other devices.
Note: The network, default gateway and DNS server is defined as that information will be passed in the DHCP message to the host requesting to be assigned an address via DHCP.
Cisco CCNA Cisco discovery protocol
Cisco Discovery Protocol (CDP) is a proprietary protocol designed by Cisco to help administrators collect information about both locally attached and remote devices.
By using CDP, you can gather hardware and protocol information about neighbor devices, regardless of the routed protocols enabled on the interface since it operates at layer 2. This is very useful information for troubleshooting and documenting your Cisco-based networks. CDP is turned on by default on all Cisco routers and switches.
Cisco CCNA Cisco Discovery Protocol
The “show cdp neighbor” command (sh cdp nei for short) delivers information about directly connected devices.
It’s important to remember that CDP packets aren’t passed through a Cisco switch, and that you only see what’s directly attached. So this means that if your a router is connected to a switch, you won’t see any of the devices hooked up to that switch, you will need to get that information from the switch itself.
Another valuable CDP command to get more information about a neighbor is the “show cdp neighbor detail” command (show cdp nei de for short). This command can be run on both routers and switches, and it displays detailed information about each device connected to the device you’re running the command on.
The “show cdp entry *” command is the same as “show cdp nei detail”. However, on a router or switch, type “show cdp entry * ?” and you’ll see there are two helpful subcommands you can use.
Cisco CCNA show cdp neighbours
Device ID – The configured ID (name), MAC address, or serial number of the neighbor device.
Local Intrfce – (Local Interface) The protocol being used by the connectivity media.
Holdtime – (Holdtime) The remaining amount of time, in seconds, the current device will hold the CDP advertisement from a transmitting router before discarding it.
Capability – The capability code discovered on the device. This is the type of the device listed in the CDP Neighbors table.
Platform – The product number of the device.
Port ID – The protocol and port number of the device.
show cdp neighbors