Skip to main content

Using the boot system command

Using the boot system command
5.1.3
This page will explain how boot system commands are used to specify the fallback boot-up sequence for Cisco IOS software.
The three figures show boot system entries. These entries specify that a Cisco IOS software image will load first from flash memory, then from a network server, and finally from ROM:
  • Flash memory - A system image can be loaded from flash memory. Information stored in flash memory is not vulnerable to network failures that can occur when system images are loaded from TFTP servers. 
  • Network server - If flash memory is corrupted, a system image can be loaded from a TFTP server. 
  • ROM - The final bootstrap option is to boot from ROM. However, a system image in ROM is usually a subset of the Cisco IOS that lacks the protocols, features, and configurations of the full Cisco IOS. Also, if the software has been updated, a router may have an older version stored in ROM.  
The command copy running-config startup-config saves the commands in NVRAM. The router will execute the boot system commands as needed in the order in which they were originally entered into configuration mode.
In the Lab Activities, students will use boot system commands to display information about the Cisco IOS image and boot procedure of a router.
The next page will describe the router configuration register.

Comments

Post a Comment

Popular posts from this blog

OSI layers / Peer-to-peer communications / TCP/IP model

OSI layers 2.3.4 This page discusses the seven layers of the OSI model. The OSI reference model is a framework that is used to understand how information travels throughout a network. The OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media. In the OSI reference model, there are seven numbered layers, each of which illustrates a particular network function. - Dividing the network into seven layers provides the following advantages: • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand. In the foll...
Post a Comment
Read more

Advantages and disadvantages of link-state routing

Advantages and disadvantages of link-state routing 2.1.5  This page lists the advantages and disadvantages of link-state routing protocols. The following are advantages of link-state routing protocols:  Link-state protocols use cost metrics to choose paths through the network. The cost metric reflects the capacity of the links on those paths. Link-state protocols use triggered updates and LSA floods to immediately report changes in the network topology to all routers in the network. This leads to fast convergence times. Each router has a complete and synchronized picture of the network. Therefore, it is very difficult for routing loops to occur. Routers use the latest information to make the best routing decisions. The link-state database sizes can be minimized with careful network design. This leads to smaller Dijkstra calculations and faster convergence. Every router, at the very least, maps the topology of it...
Post a Comment
Read more

Ports for services

Ports for services 10.2.2  Services running on hosts must have a port number assigned to them so communication can occur. A remote host attempting to connect to a service expects that service to use specific transport layer protocols and ports. Some ports, which are defined in RFC 1700, are known as the well-known ports. These ports are reserved in both TCP and UDP.  These well-known ports define applications that run above the transport layer protocols. For example, a server that runs FTP will use ports 20 and 21 to forward TCP connections from clients to its FTP application. This allows the server to determine which service a client requests. TCP and UDP use port numbers to determine the correct service to which requests are forwarded. The next page will discuss ports in greater detail.
Post a Comment
Read more