Configure Cisco router as a DHCP client

Cisco routers can be configure as both DHCP servers and DHCP clients. An interface on a router that connects to the Internet Service Provider (ISP) is often configured as a DHCP client. This way, the ISP can provide the IP information to the client device.To configure an interface as a DHCP client, the ip address dhcp interface mode command is used. Consider the following example:We have a small network consisting of a router and a DHCP server. We want to configure the interface Gi0/0 on the router Read more [...]

Configure static MAC address

Although Cisco switches dynamically build the MAC address table by using the source MAC address of the received frames, you can also manually add a MAC address to the switch’s MAC address table. The static MAC entries will be retained even after the switch is restarted.To configure a static MAC address, the following command is used:(config)#mac-address-table static MAC_ADDRESS vlan ID interface INTERFACEThe following command will permanently assign the MAC address of 1111.1111.1111┬áto the Read more [...]

Map hostnames to IP addresses

It is possible to define static hostname-to-address mappings on a Cisco device for the purpose of name resolution. This is usually done in environments without a DNS server.The mappings can be defined using the global configuration command ip host HOSTNAME IP_ADDRESS:Floor1(config)#ip host HQ_SERVER 192.168.0.100In the output above we’ve defined the IP address of 192.168.0.100 for the hostname HQ_SERVER. To display the hostname-to-address mappings, the show hosts command is used:Floor1#show Read more [...]

show interfaces status command

The status of an interface on a Cisco switch can be checked using the show interface TYPE exec mode command. Consider the following example:SW1#show interfaces fa0/1 FastEthernet0/1 is up, line protocol is up (connected) Hardware is Lance, address is 0040.0b21.0b01 (bia 0040.0b21.0b01) BW 100000 Kbit, DLY 1000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s input flow-control is off, output flow-control Read more [...]

Erasing configuration files

In certain scenarion you might want to remove the existion configuration of an Cisco IOS device and restore the device to the factory settings. To do this, you will need to access the device over the network or through the console and issue one of the following commands (not all commands are supported on all Cisco devices):write eraseerase nvram:erase startup-config Once you execute one of the commands above, you will need to reload the device. Here is an example:R1#write erase Erasing the nvram Read more [...]

Cisco Discovery Protocol (CDP) overview

CDP (Cisco Discovery Protocol) is a proprietary protocol developed by Cisco used to discovers information about the locally attached Cisco equipment. With CDP, the administrator can gather hardware and protocol information about neighboring devices, which can be helpful when troubleshooting or documenting the network.To discover information, Cisco devices send CDP messages out each of their interfaces. These messages contain information about them, such as their hostname, network and data link addresses, Read more [...]