Chp 6. Intro to Networking Flashcards
The network layer provides services to allow end devices to exchange data across the network. To accomplish this end-to-end transport, the network layer uses four basic processes:
- Addressing end devices
- Encapsulation
- Routing
- De-Encapsulation
The network layer encapsulates the protocol data unit (PDU)
from the transport layer into a packet.
Each router a packet crosses to reach the destination host is called
a hop.
Does the IP Header remain the same from the time the packet leaves the source host until it arrives at the destination host?
Yes
Best Effort IP Characteristics: (2)
Packet delivery is not guaranteed The packet may be delivered with errors
The header Differentiated Services or DiffServ (DS) field is an
is an 8-bit field used to determine the priority of each packet.
The header Time-to-Live (TTL) field
Contains an 8-bit binary value that is used to limit the lifetime of a packet.
What happens if the TTL field decrements to zero?
the router discards the packet and sends an Internet Control Message Protocol (ICMP) Time Exceeded message to the source IP address
The header Protocol Field is an 8-bit binary value that
indicates the data payload type that is being carried, which enables the network layer to pass the data to the appropriate upper-layer protocol.
IPv4 still has three major issues:
- Address Depletion
- Internet Routing and Table Expansion
- Lack of end-to-end connectivity
Ipv6 improvements to Ipv4 (5)
- Improved Packet Handling
- Larger Payload for increased throughput
- Hierarchical Architecture for routing efficiency
- Autoconfiguration for addresses
- No Need for Nat
IPv6 Packet Header: Flow Label - This 20-bit field suggests that all packets with the same flow label receive
the same type of handling by routers.
IPv6 Packet Header: Next Header - This 8-bit field is equivalent to the IPv4 Protocol field.
Identifies the application type to the upper-layer protocols
IPv6 Packet Header: Hop Limit - This 8-bit field replaces the IPv4
Time To Live (TTL) field.
IPv6 Packet Header: Traffic Class
Classifies packets for congestion control
On a Cisco IOS router, which command can be used to display the router’s IPv4 routing table
show ip route
When a router interface is configured with an IPv4 address, a subnet mask, and is activated, the following two routing table entries are automatically created:
C - Identifies a directly-connected network
L - Identifies that this is a local interface.
C - Identifies a directly-connected network. Directly-connected networks are automatically created when
an interface is configured with an IP address and activated
L - Identifies that this is a local interface.
This is the IPv4 address of the interface on the router.
What are the three Routing Table entries you need to know
Route Source Destination Network Outgoing Interface
Routing Source identifies how the
network was learned by the router
Outgoing interface identifies the exit
interface to forward a packet toward the final destination
Route TimeStamp Identifies
when the router was last heard from
Next Hop Identifies
the IP address of the next router to forward the packet.
Aux Port
A port to manage routers using telephone lines and modems
Switch Configuration Commands
Switch Configuration Tasks Commands
Configure the device name (1)
Switch> enable
Switch# configure terminal
Switch(config)# hostname rayswitch
Commands to Secure access to console port aka
Secure user EXEC mode (3)
Switch> enable
Switch# configure terminal
Switch(config)# line console 0
Switch(config)# password cisco
Switch(config)# login
Secure Remote Telnet/SSH Access (3)
Switch> enable
Switch# configure terminal
Switch(config)# line vty 0 15
Switch(config)# password cisco
Switch(config)# login
Secure Privileged Exec Mode: (1)
Secure all passwords in the config file: (1)
Switch(config)# enable secret password
Switch(config)# service password-encryption
These are usually turned on at the same time
Provide Legal Notification aka banner message (1)
Switch> enable
Switch# configure terminal
Switch(config)# banner motd ” Place the keep out message here”
Configure VLANS (Remote access) or Configure the management SVI
Switch> enable
Switch# configure terminal
Switch(config)# interface vlan 1
Switch(config)# ip address 10.18.0.19 255.255.255.0
Switch(config)# no shutdown
Switch(config)# end
Save Running Configuration
R1# copy running-config startup-config
What is not required but good practice to perform when configuring a networking device?
configure a description on each interface to help document the network information.
The description text is limited to 240 characters.
Commands to add a description to router aka as adding documentation (4)
R1# conf t
R1(config)# interface type_space_number
R1(config)# ip address subnet mask
R1(config)# description anything you type afte description will show up on scree,
R1(config)# no shutdown
Exp: interface gigabitethernet 0/0
What do the coded int the IPv4 routing table codes in the comman line:
C – ?
S – ?
D – ?
* – ?
C – directly connected
S – static
D – EIGRP
* – candidate default
Which two pieces of information are in the RAM of a Cisco router during normal operation?
- The IP routing table
- The Cisco IOS file is stored in flash memory and copied into RAM during the bootup.
Startup configuration file in a cisco router is stored in..
NVRAM
The connections in a Cisco 1941 router include two types of ports that are used for initial configuration and command-line interface management access. The two ports are the regular RJ-45 port and a new USB Type-B (mini-B USB) connector. In addition, the router has an AUX port for remote management access, and two Gigabit Ethernet interfaces for LAN access. Compact Flash can be used increase device storage, but it does not perform the functions of the CPU, which is required for operation of the device.
What are two types of router interfaces?
LAN interfaces – Used for connecting routers to each other.
WAN interfaces – Used for connecting routers to external networks, usually over a larger geographical distance.
A router boots and enters setup mode. What is the reason for this?
The configuration file is missing from NVRAM.
When a connectionless protocol is in use at a lower layer of the OSI model, how is missing data detected and retransmitted if necessary?
Upper-layer connection-oriented protocols keep track of the data received and can request retransmission from the upper-level protocols on the sending host.
