DHCP relay agent

When a device is configured as a DHCP client, it will send a a broadcast packet to discover DHCP servers on the network. Broadcast packets are not forwarded by routers by default, so if a DHCP server is in a different network than the DHCP client, it will not receive the request. Consider the following scenario:The workstation on the left is configured as a DHCP client. R2 on the right is configured as a DHCP server. The workstation sends a DHCP discover packet, but it receives no request, since Read more [...]

Configure timezone and Daylight Saving Time (DST)

It is recommended to set the correct timezone and adjust the DST setting before configuring a router as an NTP client. The syntax of the command used to set the timezone is:(config)clock timezone NAME HOURS [MINUTES]The name of the timezone can be anything you like. After the name parameter, you need to specify the difference in hours (and optionally minutes) from Coordinated Universal Time (UTC). For example, to specify the Atlantic Standard Time, which is 4 hours behind UTC, we would use the following Read more [...]

Default static route

A default route defines where packets will be sent if no specific route for the destination network is listed in the routing table. If no default route is set, the router will discard all packets with destination addresses not found its routing table.Consider the following example: We have a network of three routers. R1 is directly connected to two subnets – 192.168.0.0/24 and 10.0.0.0/24. R3 is connected to the Internet.Here is the routing table on R1:R1#show ip route Gateway of last resort Read more [...]

The ARP table on a Cisco router

Just like regular hosts, if a Cisco router wants to exchange frames with a host in the same subnet, it needs to know its MAC address. The IP-to-MAC address mapping are kept in the router’s ARP table. Consider the following example:R1 has two connected subnets – 10.0.0.0/24 and 172.16.0.0./16. Before exchanging frames with either host, R1 will need to know their MAC addresses. Here is the output of the R1’s ARP table:R1#show ip arp Protocol Address Age (min) Hardware Addr Read more [...]

Uniform Resource Locator (URL) structure

An URL is a string of characters that contains information about how to fetch a resource from its location. An URL specifies the primary access mechanism and the network location of a resource. A typical URL consists of the following components:the protocol used to connect to the server (e.g. HTTPS)the server hostname (e.g. geek-university.com)the document path (e.g. /course) Here is a graphical representation of these components:URLs can also be used to reference documents other than the web Read more [...]

Create a static host route

In one of the previous lessons we’ve defined a static route for a specific subnet by using the subnet mask of 255.255.255.0 in the ip route command. IOS also allows you to specify a static host route for a single host by specifying the 255.255.255.255 (/32) subnet mask in the ip route command.Static host routes are usually used when redundant paths exist. Consider the following example:In the example above you can see that we have a network of three routers and a switch connected to the 10.0.0.0/24 Read more [...]