LESSON 8.3 C700 SECURE NETWORK
DESIGN QUESTIONS WITH CORRECT
ANSWERS
In meshes - ANSWER-How are routers organized?
Gives ore reliability because it allows many possible alternative routes between endpoints - ANSWER-Why are routers organized in meshes?
find all rows that apply to an incoming packet. - ANSWER-What must a router do first when routing a packet? It will will look at every row in the table to see if it is a match to the packet's destination and pick the best alternative route from the list of matches.
routing table - ANSWER-What does a router use to help make routing decisions?
rows; a route for a range of IP addresses - ANSWER-What does a routing table have? What do they represent?
No, it only needs a row for each group of IPv4 addresses - ANSWER-Does a routing table need a row for each IPv4 address?
Yes - ANSWER-Do routers perform calculation on all rows?
Steps 1. find which of the rows in the routing table match the destination IPv4 address in an arriving packet - ANSWER-What is step 1 out of 3 in how a router use its routing table to make routing decisions?
Find the best-match row with the longest match (initial 1s in the row mask) - ANSWER-
What is step 2 out of 3 in how a router use its routing table to make routing decisions?
if there is a tie on longest match, select among the tie rows based on: cost for metric (choose row with longest metric value) or speed metric (choose row with highest metric value) - only when needed - ANSWER-What is the tie-breaker rule in step 2 out of 3 in how a router use its routing table to make routing decisions?
Send the packet back out the interface designated in the best match row - ANSWER-
What is step 3 out of 3 in how a router use its routing table to make routing decisions? It uses the Destination Network or Subnet column and the Mask columns - ANSWER-
How does the router know which IPv4 addresses match a row?
Default Row - ANSWER-Row ensures that at least one row will match the destination IPv4 address of every arriving packet. Has the destination 0.0.0.0 and the mask 0.0.0.0
next-hop router - ANSWER-the router will send the packet to another router; next hop column specifies the router that should receive the packet
decision cache - ANSWER-a router may cache (remember) the decision it made for a destination IPv4 Address and use this decision for successive IPv4 packets going to the same destination. (greatly reduces the work that router will do for each successive packet to the same destination address.)
if used for too long will result in non-optimal routing or even routes that will not work and will effectively send packets into a black hole - ANSWER-Why is decision cache not safe?
go through the entire 3 steps for each - ANSWER-What should a router do if it receives several packets going to the same destination IPv4 address?
the router would simply repeat the decision instead of going through all three steps each
time. - ANSWER-How would decision caching speed the routing decision for packets after the first one?
The same columns that routing tables for IPv4 address have but arriving packets, mask, an destination IP network and subnet are is 128-bit - ANSWER-How do routing tables for IPv6 address look?
Version number field - ANSWER-What do the IPv4 packet first four bits constitute?
Version number field (term) - ANSWER-has the value 0100 (binary for 4) Indicates this is an IPv4 packet
Version, Header length, differentiated services control point, ECN, Total length - ANSWER-What constitute the first row of a IPv4 packet?
Differentiated services control point - ANSWER-use to request special services, such as priority or other quality of service purposes.
Explicit Congestion Notification (ECN) - ANSWER-Notify the receiver of congestion along the route
Destination host uses to reassemble fragmented packets - ANSWER-The second row of IPv4 packet information.
DESIGN QUESTIONS WITH CORRECT
ANSWERS
In meshes - ANSWER-How are routers organized?
Gives ore reliability because it allows many possible alternative routes between endpoints - ANSWER-Why are routers organized in meshes?
find all rows that apply to an incoming packet. - ANSWER-What must a router do first when routing a packet? It will will look at every row in the table to see if it is a match to the packet's destination and pick the best alternative route from the list of matches.
routing table - ANSWER-What does a router use to help make routing decisions?
rows; a route for a range of IP addresses - ANSWER-What does a routing table have? What do they represent?
No, it only needs a row for each group of IPv4 addresses - ANSWER-Does a routing table need a row for each IPv4 address?
Yes - ANSWER-Do routers perform calculation on all rows?
Steps 1. find which of the rows in the routing table match the destination IPv4 address in an arriving packet - ANSWER-What is step 1 out of 3 in how a router use its routing table to make routing decisions?
Find the best-match row with the longest match (initial 1s in the row mask) - ANSWER-
What is step 2 out of 3 in how a router use its routing table to make routing decisions?
if there is a tie on longest match, select among the tie rows based on: cost for metric (choose row with longest metric value) or speed metric (choose row with highest metric value) - only when needed - ANSWER-What is the tie-breaker rule in step 2 out of 3 in how a router use its routing table to make routing decisions?
Send the packet back out the interface designated in the best match row - ANSWER-
What is step 3 out of 3 in how a router use its routing table to make routing decisions? It uses the Destination Network or Subnet column and the Mask columns - ANSWER-
How does the router know which IPv4 addresses match a row?
Default Row - ANSWER-Row ensures that at least one row will match the destination IPv4 address of every arriving packet. Has the destination 0.0.0.0 and the mask 0.0.0.0
next-hop router - ANSWER-the router will send the packet to another router; next hop column specifies the router that should receive the packet
decision cache - ANSWER-a router may cache (remember) the decision it made for a destination IPv4 Address and use this decision for successive IPv4 packets going to the same destination. (greatly reduces the work that router will do for each successive packet to the same destination address.)
if used for too long will result in non-optimal routing or even routes that will not work and will effectively send packets into a black hole - ANSWER-Why is decision cache not safe?
go through the entire 3 steps for each - ANSWER-What should a router do if it receives several packets going to the same destination IPv4 address?
the router would simply repeat the decision instead of going through all three steps each
time. - ANSWER-How would decision caching speed the routing decision for packets after the first one?
The same columns that routing tables for IPv4 address have but arriving packets, mask, an destination IP network and subnet are is 128-bit - ANSWER-How do routing tables for IPv6 address look?
Version number field - ANSWER-What do the IPv4 packet first four bits constitute?
Version number field (term) - ANSWER-has the value 0100 (binary for 4) Indicates this is an IPv4 packet
Version, Header length, differentiated services control point, ECN, Total length - ANSWER-What constitute the first row of a IPv4 packet?
Differentiated services control point - ANSWER-use to request special services, such as priority or other quality of service purposes.
Explicit Congestion Notification (ECN) - ANSWER-Notify the receiver of congestion along the route
Destination host uses to reassemble fragmented packets - ANSWER-The second row of IPv4 packet information.
