ICND1 Certification Exam: Network Devices and Services
You can be sure to get a few questions on the Cisco ICND1 certification exam that tests your knowledge of types of devices and different network services. The following are some key points to remember about devices and services:
Hub: A hub is a layer 1 device that is used to connect systems together. When a hub receives data in the form of an electrical signal it sends the data to all other ports in hopes the destination system is at one of those ports. All ports on the hub create a single collision domain and a single broadcast domain.
Repeater: A repeater is a layer 1 device that is used to re-amplify the signal. As the signal travels along the network it gets weaker due to interference so the purpose of the repeater is to regenerate that signal so it can travel more distance.
Bridge: A bridge is a layer-2 device that creates multiple network segments. The bridge maintains a table in memory of what systems reside on what segments by their MAC addresses. When data reaches the bridge, the bridge filters the traffic by only sending the data to the network segment that the destination system resides on.
The purpose of the bridge is that it filters traffic by only sending the data to the segment where the destination system resides. Each segment on the bridge creates a separate collision domain, but it is all one broadcast domain.
Switch: The switch, another layer-2 device, is an improvement on a bridge in the sense that each port on the switch acts as a network segment. The switch filters traffic by only sending the data to the port on the switch where the destination MAC address resides. The switch stores each MAC address and the port the MAC address resides on in an area of memory known as the MAC address table. Each port on the switch creates a separate collision domains but all ports are part of the same broadcast domain.
Router: A router is a layer-3 device that handles routing of data from one network to another network. The router stores a listing of destination network in the routing table which is found in memory on the router.
DHCP: The DHCP service is responsible for assigning IP addresses to hosts on the network. When a client boots up it sends a DHCP discover message, which is a broadcast message designed to locate a DHCP server. The DHCP server responds with a DHCP Offer — offering the client an IP address. The client then responds with a DHCP request message asking for the address before the server responds with a DHCP ACK to acknowledge that the address has been allocated to that client.
DNS: The DNS service is responsible for converting the Fully Qualified Domain Name (FQDN) such as www.gleneclarke.com to an IP address.
NAT: Network Address Translation is responsible for converting the internal address to a public address that is used to access the Internet. NAT offers the benefit of being able to only purchase one public IP addresses and have a number of clients on the network use that one IP address for Internet access.
NAT also offers the security benefit that the internal addresses are not used on the Internet - helping to keep the internal addresses unknown to the outside world. There are two types of NAT to know for the CCENT certification exam:
Static NAT: Static NAT is the mapping of one internal address to one public address. With static NAT you will need multiple public addresses to allow internal clients to access the Internet.
NAT Overloading: A more popular form of NAT, NAT overloading is the concept that all internal addresses get translated to the one public address on the NAT device.
Web Services: There are a number of web services you should be familiar with for the CCENT certification exam.
Consider the following:
POP3/IMAP4: POP3 and IMAP4 are the Internet protocols for receiving email over the Internet.
SMTP: SMTP is the Internet protocol for sending email over the Internet. SMTP servers are also known as email servers.
HTTP: HTTP servers are also known as web servers, and are used to host websites. HTTP is a protocol that is used to send the web page from the web server to the web client.
FTP: FTP is an Internet protocol used to transfer files over the Internet. The files are hosted on FTP servers which are then downloaded to any clients on the Internet.