Wednesday, February 10, 2016

CCNAv1 Chapter 6 Notes

Chapter 6
Network Layer
  • Four Processes
    • 1. Addressing End Devices
      • IP Addresses, must be unique. (Within network)
    • 2. Encapsulation
      • Receives a PDU from the transport layer, adds the IP information for destination and source. At this point the PDU is now called a packet.
    • 3. Routing
      • Directs packets to destinations on remote networks. (LANs use Switching)
    • 4. Decapsulation
      • Checks the IP header- if it is the destination, the IP header is removed and the PDU is sent to the transport layer.

  • Network Layer Protocols
    • IPv4
      • 4.2 Billion
    • IPv6
      • 340 undecillion
    • IP
  • Connectionless: No link with remote site before sending.
    • Unreliable; called ‘best effort’
    • Media Independent
  • Developed in 1983 by arpnet.


  • IPv4 Header
    • Version
      • IPv4 value 0100

  • Differential Services
    • Determines Priority

  • TTL (Time to Live)
    • Limits life of a packet.

  • Protocol - Data Payload Type
  • ICMP
  • Used to send error messages /  control messages.

  • TCP/UDP
  • Source IP
  • Destination IP

  • ID - Router might have to split the packet when transferring
  • Flags  between types.
  • Fragment Offset
Why IPv6?
(Over IPv4)
  • Running out of IPv4 Addresses.
  • Routing tables get too large.
  • Lack of end to end connectivity.

(For IPv6)
  • Increased address space. (128bits vs 320bits)
  • Improved packet handling. (fewer header fields)
  • Eliminates the need for NAT.
  • Integrated security.

IPv6 Header
  • Version (IPv6 = 0110)
  • Traffic Clas
  • Author's Note: This is a screenshot from our school PC's cmd.

    It won't be the same if you try to replicate the same command from your PC. 

    • Equal Capture.PNG

  • Flow Label
    • Real time apps
  • Payload Length
  • Next Header
    • IPv4 Protocol Field
  • Hop Limit
    • Same as TTL
  • Source Address
  • Destination Address

IPv4
25: Local Default Route

281: Local Network Addr

306: Loopback

276: Wifi?

276/306/281: Multicast

Same as ^: Limited Broadcast IP Address

IPv6
Ipv6 loopback
local link network addr
global unicast ip addr
ipv6 reserved multicast addr


Things to learn from ‘show ip route’;
 D - Learned
 C - Connected
 L - Local
 S - Static
 O - OSPF

A B C
C | 192.168.10.0/24 is directly connected, GigabitEthernet0/0
L  | 192.168.10.1/32 is directly connected, GigabitEthernet0/0

A B      C       D                    E                                   G
D | 10.1.1.0/24 [90/2170112] via 209.165.200.226, 00:00:05, Serial0/0/0

A: Identifies how the network was learned by the router.
B: Identifies the destination network and how it’s connected.
C: Identifies the interface on the router. (Administrative distance)
D: Identifies the metric to reach the remote network. (Smaller the number, better the route)
E: Identifies the next IP hop address to reach the remote network.
F: Identifies the amount of elapsed time since network was discovered.
G: Identifies the outgoing interface on the router to reach the destination network.

Show Version
  • Memory
  • Interfaces it has / kinds
  • Non-volatile config memory
  • How much flash it has
  • ROM Info
  • OS info

Router Configuration Steps
 > enable Shortened: en
 # config t Shortened: config t
 # hostname R1 Shortened: #ho R1
 # enable secret class

 # line console 0
 L# password cisco
 L# login
 L# exit

 # line vty 0 4 (Telnet/SSH)
 # password cisco
 # login
 # exit

 # service password-encryption
 # copy running-config startup-config Shortened: wr / copy run start
 # banner motd #
Configuring LAN Interfaces (Gigabit / Ethernet)
R1:
 # config t
 # int G0/0
 if# ip address 192.168.1.1 255.255.255.0
 if# description Link to LAN-10
 if# no shutdown
 if# exit
 #
 # int g0/1
 if# ip add 192.168.11.1 255.255.255.0
 if# no shut
 if# exit
 

Verify Interface Configuration
#show ip interface brief
-  Status should be up.
-  Administratively down means they haven’t been ‘no shutdown’
-  Port should be up.

Default Gateways on a Host
  • If you’re pinging a local host (does not pass through a RT) you don’t need a gateway, otherwise you do.

honey came in and she caught me red handed creeping with the girl next door;
Picture this we were both naked bangin on the bathroom floor.
How could I forget that I had given her the extra hey.
All this time she was standing there she never took her eyes off me.

Review Questions A
What IPV4 header field defines packet priority?
  • Differentiated Services

Why do we not need IPV6?
  • There are enough addresses for all devices.

What is the router boot sequence?
  • Preform POST
  • Load Bootstrap
  • Find/Get IOS
  • Locate Startup Config & Load

What prompt was the command entered at?
  • Enable
    • R1>
  • Login
    • R1(config-line)#
  • Interface FastEthernet 0/0
    • R1(config)#
  • copy running-config startup-config
    • R1#
  • No Shutdown
    • R1(config-if)#

What are the two commands in windows to display the routing table?
  • netstat -r
  • route print

You are working on a router after making several changes w/o saving the power is lost. What 3 types of info is lost?
  • Running Configuration
  • IP Routing Table
  • ARP Table

What are the 2 types of interfaces that allow access via the vty lines?
  • LAN
  • WAN
What command saves the current config so the system will use it on next boot?
  • WR or copy running-config startup-config

For a manual pc network configuration, what 4 pieces of information have to be entered?
  • IP Address
  • Subnet Mask
  • Default Gateway
  • DNS Server

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