The Network Layer Chap 6 Flashcards
4 basic processes of the Network layer
addressing end devices
encapsulation
routing
de-encapsulation
3 basic charecteristics of IP
connectionless
best effort(unreliable)
media independent
what happens if out-of-order or missing packets create problems for the application using the data?
upper layer services, such as TCP, must resolve the issue
What is the only major characteristic of the network-layer of the media considers?
the maximum size of the PDU that each medium can transport or the maximum transmission unit (MTU)
what is it called when and intermediate device such as a router must split up a packet when forwarding it from one medium to a medium with a smaller MTU?
fragmenting the packet or fragmentation
What are the 2 parts to an IPv4 packet?
IP header and Payload
What are the 6 significant fields in an IPv4 header?
- version 2. Differentiated Services(DS) 3. TTL 4. Protocol 5. Source IP 6. Destination IP
what is the 8 bit ipv4 header field that indicates the data payload type that the packet is carrying?
Protocol field
Which ipv4 packet header field uses the traceroute command to identify routers used between source and destination?
TTL field
Which ipv4 packet header field is used to determine the priority of each packet?
Differentiated Serviced (DS)
Which ipv4 packet header field is used to identify the ip packet version?
version field
What is the ipv4 version field always set to?
0100
Which ipv4 packet header field identifies the number of 32-bit words in the header?
internet header length
Which ipv4 packet header field error checks the ip header
header checksum
What happens to the packet if the header checksum is incorrect
the packet is dropped
Which ipv4 packet header field defines the entire packet size?
total length
what is the size range a packet can be?
20 bytes to 65535 bytes
what is the size of a packet header?
20 bytes
What are 3 limitations of IPv4
- IP address depletion 2. Internet routing table depletion 3. Lack of end to end connectivity
Advantages of IPv6
- Improved packet handling 2. eliminate the need for NAT 3. Integrated security
how many addresses does ipv4 provide?
4.2 million
how many addresses does ipv6 provide?
340 undecillion
how many header fields does ipv6 have?
8 fields
4 advantages ipv6 headers offer over ipv4 headers?
- Better routing efficiency for performance and forwarding-rate scalability
- No requirement for processing checksums
- Simplified and more efficient extension header mechanisms ( as opposed to the ipv4 options field)
- A flow label field for per-flow processing with no need to open the transport inner packet to identify the various traffic flows
what are the 8 fields in an ipv6 packet header?
Version, traffic class, flow label, payload length, next header, hop limit, source ip address, destination ip address
Which ipv6 header field is equivalent to the ipv4 DS field?
traffic class field
what is the version number in an ipv6 version header filed always set to?
0110
Which ipv6 packet header can be used to inform routers and switches to maintain the same path for the packet flow so that packets are not reordered?
flow label
Which ipv6 packet header is equivalent to the ipv4 protocol field?
next header
Size of the IPV6 header version
4 bits
Size of the IPV6 header traffic class
8 bit
Size of the IPV6 header flow label
20 bit
Size of the IPV6 header payload length
16 bit
Size of the IPV6 header next header
8 bit
Size of the IPV6 header hop limit
8 bit
Size of the IPV6 header source address
128 bit
Size of the IPV6 header destination address
128 bit
A host can send packets to which 3 destinations?
itself, local host, remote host
what is the router connected to the local network segment referred to as?
default gateway
what command can be used on a Windows host to display the host routing table?
route print or netstat -r
what is the address for the local default route, the route with destinations do not match other specified addresses in the routing table?
0.0.0.0
What is the range for loopback addresses?
127.0.0.0 - 127.255.255.255
which command is used to display the routing table in a cisco ios router
show ip route
Identifies a directly connected network. Directly connected networks are automatically created when an interface is configured with an IP address and activated.
c
Identifies that this is a link local route. Link local routes are automatically created when an interface is configured with an IP address and activated.
L
Identifies that the route was manually created by an administrator to reach a specific network. This is known as a static route.
S
Identifies that the route was learned dynamically from another router using the Enhanced Interior Gateway Routing Protocol (EIGRP)
D
Identifies that the route was learned dynamically from another router using the Open Shortest Path First (OSPF) routing protocol.
O
In a routing table, what identifies the trustworthiness of the route source?
administrative distance
In a routing table, what identifies the value assigned to reach the remote network? Lower values indicate preferred networks
metric
In a routing table, what identifies the IP address of the next router to forward the packet
next-hop
In a routing table, what identifies when the route was last heard from?
route timestamp
in a routing table, what identifies the exit interface to use to forward a packet toward the final destination?
Outgoing interface
in a routing table, what identifies the address of the remote network?
destination network
in a routing table, what identifies how the route was learned?
route source
What is the address of the device that will process the packet next?
next hop
What do Cisco devices require to execute OS instructions, such as system initialization, routing functions, and switching functions.
CPU
system software used in most cisco devices regardless of the size and type of the device.
cisco internetwork operating system (IOS)
Volatile memory that requires continual power to maintain its information.
Random access memory RAM
Memory that stores the bootup instructions
ROM
Memory that contains the startup configuration
NVRAM
Non volatile Memory that contains the IOS
Flash
Memory that contains the running configuration files
RAM
Memory that contains a limited IOS in case the router cannot load the full version
ROM
Memory that contains the basic diagnostic software
ROM
Memory that contains the ip routing and ARP tables
RAM
Memory that contains basic diagnostic software
ROM
Memory that contains the packet buffer
RAM
Router component that connects routers to external networks usually over a large distance
WAN interface
A way to remotely access the CLI across a network interface
Telnet or SSH
Router component that connects computers, switches, and routers for internal networking.
LAN interface
A local port on a router which uses USB or low-speed, serial connections to manage network devices.
Console port
A port to manage routers using telephone lines and modems
aux port
What is the first step in a router boot up process and which part of the router does it boot this process from?
Perform POST and load the bootstrap from ROM.
What is the second step in a router boot up process and which part of the router does it boot this process from?
Locate and load the Cisco IOS software from either flash, a TFTP server, or ROM
What is the third step in a router boot up process and which part of the router does it boot this process from?
Locate and load the configuration file from either NVRAM, a TFTP server, or the console port.
What program searches for the configuration file?
the bootstrap program
Where is the IOS typically located before startup
flash memory
Where does the router look for the IOS if it is not found in flash?
tftp server, but if a full ios image is not located there, a scaled down version can be found in ROM
Which show command is used to verify and troubleshoot some of the basic hardware and software components of the router?
show version
global configuration command to prevent passwords from displaying as plain text in the configuration file.
service password-encryption
what command activates an interface?
no shutdown
Which show command of all interfaces, their ip addresses, and their current status?
show ip interface brief
which show command displays the contents of the ipv4 routing table stored in ram?
show ip route
which show command displays statistics for all interfaces on the device?
show interface
which show command displays the ipv4 statistics for all interfaces on a router?
show ip interface