Tag - Vlans

CCNA Labs Scenario

Scenario Labs For CCNA

  1. Setting up a Serial Interface 
  2. CDP
  3. IP Addressing
  4. Static Routes
  5. Default Routes
  6. RIP Routes
  7. IGRP Routes
  8. Using Loopback Interfaces
  9. RIP v2 Routes
  10. CHAP and RIP
  11. Standard Access-Lists with RIP
  12. Extended Access-Lists with RIP
  13. EIGRP Routes
  14. OSPF Routes
  15. Static NAT
  16. Many to One NAT
  17. NAT Pool
  18. Telnet
  19. 2950 IP Addresses
  20. 2950 Trunk
  21. 2950 Trunk (Dynamic)
  22. 2950 VLANs
  23. 2950 Deleting VLANs
  24. 2950 VTP
  25. 2950 VTP w/ client
  26. 2950 Telnet

DHCP FAQ

Questions

  1. General
    1. What is DHCP?
    2. What is DHCP’s purpose?
    3. Who Created It? How Was It Created?
    4. Can DHCP work with Appletalk or IPX?
    5. How is it different than BOOTP or RARP?
    6. How is it different than VLANs?
    7. What protocol and port does DHCP use?
    8. What is an IP address?
    9. What is a MAC address?
    10. What is a DHCP lease?
    11. What is a Client ID?
    12. Why shouldn’t clients assign IP numbers without the use of a server?
    13. Can DHCP support statically defined addresses?
    14. How does DHCP and BOOTP handle other subnets?
    15. Can a BOOTP client boot from a DHCP server?
    16. Can a DHCP client boot from a BOOTP server?
    17. Is a DHCP server “supposed to” be able to support a BOOTP client?
    18. Is a DHCP client “supposed to” be able to use a BOOTP server?
    19. BOOTP client boot from a DHCP and BOOTPserver
    20. Can a DHCP server back up another DHCP server?
    21. When will the server to server protocol be defined?
    22. Is there a DHCP mailing list?
    23. In a subnetted environment, how does the DHCP server discover what subnet a request has come from?
    24. If a single LAN has more than one subnet number, how can addresses be served on subnets other than the primary one?
    25. If a physical LAN has more than one logical subnet, how can different groups of clients be allocated addresses on different subnets?
    26. Can DHCP support remote access?
    27. Can a client have a home address and still float?
    28. How can I relay DHCP if my router does not support it?
    29. How do I migrate my site from BOOTP to DHCP?
    30. Can you limit which MAC addresses are allowed to roam?
    31. Is there an SNMP MIB for DHCP?
    32. What is DHCP Spoofing?
    33. How long should a lease be?
    34. How can I control which clients get leases from my server?
    35. How can I prevent unauthorized laptops from using a network that uses DHCP for dynamic addressing?
    36. What are the Gotcha’s?
  2. Info on Implementations
    1. What features or restrictions can a DHCP server have?
    2. What are the DHCP plans of major client-software vendors?
    3. What Routers forward DHCP requests?
    4. What Routers include DHCP servers?
    5. What Routers use DHCP to configure their IP addresses?
    6. Which implementations support or require the broadcast flag?
    7. What servers support secondary subnet numbers?
    8. What servers support RFC-based dynamic DNS update?
    9. Do any servers limit the MAC addresses that may roam?

Broadcast Domain

A broadcast domain is simply the group of end hosts that will receive a broadcast sent out by a given host. For example, if there are ten host devices connected to a switch and one of them sends a broadcast, the other nine devices will receive the broadcast. All of those devices are in the same broadcast domain.

Of course, we probably don’t want every device in a network receiving every single broadcast sent out by any other device in the network! This is why we need to know what devices can create multiple, smaller broadcast domains. Doing so allows us to limit the broadcasts traveling around our network – and you might be surprised how much traffic on some networks consists of unnecessary broadcasts.

broadcast-domain

Using the OSI model, we find devices such as hubs and repeaters at Layer One. This is the Physical layer, and devices at this layer have no effect on broadcast domains.

At Layer Two, we’ve got switches and bridges. By default, a switch has no effect on broadcast domains; CCNA candidates know that a switch will forward a broadcast out every single port on that switch except the one upon which it was received. However, Cisco switches allow the creation of Virtual Local Area Networks, or VLANs, that are logical segments of the network. A broadcast sent by one host in a VLAN will not be forwarded out every other port on the switch. That broadcast will be forwarded only out ports that are members of the same VLAN as the host device that sent it.

The good news is that broadcast traffic will not be forwarded between VLANs. The bad news is that no inter-VLAN traffic at all is allowed by default! You may actually want this in some cases, but generally you’re going to want inter-VLAN traffic. This requires the use of a router or other Layer 3 device such as a Layer 3 Switch. (Layer 3 Switches are becoming more popular every day. Basically, it’s a switch that can also run routing protocols. These switches are not tested on the CCNA exam.)

That router we just talked about also defines broadcast domains. Routers do not forward broadcasts, so broadcast domains are defined by routers with no additional configuration.

Knowing how broadcasts travel across your network, and how they can be controlled, is an important part of being a CCNA and of being a superior network administrator. Best of luck to you in both of these pursuits!

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