Network Layer Flashcards
What does the Network Layer perform?
Addressing end devices
Encapsulation
Routing
De-encapsulation
When does the IP addressing information change in a packet?
Only when it reaches the destination or when it is translated by the device performing NAT.
What are the properties of IP?
Connectionless (no connection established with destination) Best Effort (unreliable, packet deliver not guaranteed) Media Independent (ie. copper, fiber-optic, wireless)
What is a MTU?
Maximum transmission unit. Established between data link layer and network layer. Determines how large packets can be. If forwarding to a smaller MTU, a router will fragment the packet. This can cause latency.
What makes up a IPv4 header?
Version - identifies as IPv4
Differentiated Services (DS) - priority of packet
Header Checksum - detects corruption
Time to Live (TTL) - how many hops before router discards packet
Protocol - identifies next level protocol
Source and Destination IPv4 address
What makes up a IPv6 header?
Version - identifies as IPv6
Traffic Class - priority of packet
Flow Label - informs device to handle identical flow labels the same way
Payload length - indicates length of payload/data
Next Header - next level protocol
Hop Limit
Source and Destination IPv6 address
What is the difference between IPv6 and IPv4 header?
IPv6 header is much more simplified than IPv4 header but is still similar size. This makes it easier to handle the packet.
Hosts can send packets to?
itself - loopback interface 127.0.0.1 or ::1
local host - destination host on the same local network
remote host - destination host on a remote network
default gateway
What is a loopback interface?
when you send packets to yourself to test the TCP/IP protocol stack is in effect
What types of routes are stored in a routing table
Directly-connected networks - active router interfaces
Remote networks - connected to other routers, learned through static config or dynamic routing protocol
Default route - gateway of last resort
Properties of static routing
good for small networks, used with dynamic routing protocol for configuring a default route. must be manually configured and updated.
Properties of dynamic routing?
automatically learns about remote networks, maintains up-to-date routing information, chooses best path to destination networks, attempts new best path if current path no longer available
What command do you use to view the IPv4 routing table on CISCO IOS router
show ip route in privileged EXEC mode
What letter is used to represent directly connected local interface IP address in CISCO routing table?
L
What letter is used to represent directly connected network in CISCO routing table?
C
