Routing Flashcards
Generalize the Routing Proccess
Routers receive the frame Checks for FCS error If error, drop frame If no error de-encapsulate into packet Read destination IP Check IP Routing Table for route Re-encapsulate packet into frame Send off frame
What first happens when a router receives a frame?
The router checks for any FCS errors. If there are any errors the frame is dropped. If there are no errors the Router will confirm that the MAC address was destined for the router
What happens after a router confirms that a frame was sent to it?
The packet is de-encapsulated.
The data-link header and trailer are discarded leaving only the IP packet.
What does a router do after a frame has been de-encapsulated?
The destination IP address of the packet will checked against the IP Routing Table.
Depending on the “Routing Protocol”, a destination will be set for the packet to be forwarded.
Extra info will be sent with the packet in order to tell the next router where to send the packet.
What happens after the a received packet is given a destination for routing?
The packet is encapsulated into a frame.
B/c it is being forwarded a data-link header and trailer is attached to the packet.
In HDLC and PPP encapsulation is simple.
What are connected routes?
Added by the use of the configuration of the “ip address int # “ subcommand.
Given to interfaces.
What are static routes?
Added by the use of the “ip route” global command.
What are routing protocols?
Added as a function by configuration on all routers
Resulting in a process by which routers “dynamically” tell each other about the network so that they all learn routes.
What are local routes?
Defines a route for the one specific IP address configured on the router interface.
Briefly describe Routed Protocols. What are some examples?
Carries user data
Each router making independent decisions in determining paths
EX: IPv4, IPv6
Briefly describe Routing Protocols. What are some examples?
Communicate info about networks
determine the best route b/t networks
EX: EIGRP (bandwidth and delay), OSPF (bandwidth), RIP (hop-count)
Briefly describe Static Routes. What are the advantages and disadvantages?
Routes are manually entered
Default routes or Gateway of last resort => tells router where to go if no specific route to send packet
Advantages:
No overhead on network
Disadvantages:
Manual update required when topology changes
Briefly describe Dynamic Routes.
Uses a routing protocols
Automatically adjusts based on topology changes or traffic changes
Learns and maintains routes by exchanging network updates w/ each other
can enable be enabled w/ less commands
What is AS? Describe AS. What is IGPs? What is EGPs?
AS = Automated Systems
AS is a grouping of networks in a single administrative domain
IGPs = Interior (or internal) Gateway Protocols => w/n AS
EGPs = Exterior (or external) Gateway Protocols => outside AS
What is an AS number?
W/n an AS no need to register or apply for an AS number
When communicating onto the internet apply for an AS number