IP Routing Questions 2
Question 1
Explanation
In the five above routes, there are only three different routes which are 10.0.0.0/30 and 10.0.0.0/16 and 10.0.0.1/32. Since each of these routes has a different prefix length (subnet mask), they’re considered different destinations, and they will all be installed in the routing table.
The prefix 10.0.0.0/30 was learned from three different routing protocols IBGP, RIP and OSPF so the route with lowest AD would be chosen. The AD of IBGP is 200 and the AD of RIP is 120 so for the prefix 10.0.0.0/30, only the OSPF route has the lowest AD (110) and it would be chosen to install into the routing table.
In fact this question should have three answers (including answer E), not sure why it only allows to choose two.
Question 2
Explanation
The subnet 10.10.1.20/30 covers the destination 10.10.1.22 as this subnet ranges from 10.10.1.20 to 10.10.1.23 so it is the correct answer.
Question 3
Question 4
Explanation
A router evaluates routes in the following order.
1. Prefix Length – The longest-matching route is preferred first. Prefix length trumps all other route attributes.
2. Administrative Distance – In the event there are multiple routes to a destination with the same prefix length, the route learned by the protocol with the lowest administrative distance is preferred.
3. Metric – In the event there are multiple routes learned by the same protocol with same prefix length, the route with the lowest metric is preferred. (If two or more of these routes have equal metrics, load balancing across them may occur.)
Question 5
Question 6
Question 7
Question 8
Explanation
Floating static routes are static routes that have an administrative distance greater than the administrative distance (AD) of another static route or dynamic routes. By default a static route has an AD of 1 then floating static route must have the AD greater than 1. Floating static route has a manually configured administrative distance greater than that of the primary route and therefore would not be in the routing table until the primary route fails.
Question 9
Question 10
Explanation
R1 uses the last entry (B* 0.0.0.0/0 …) to reach the Internet. The symbol * means this is a default route.
Question 11
Explanation
The static route has the Administrative Distance of 1 so it is preferred over other popular routing protocols.
Question 12
Explanation
Floating static routes are static routes that have an administrative distance greater than the administrative distance (AD) of another static route or dynamic routes. By default a static route has an AD of 1 then floating static route must have the AD greater than 1. Floating static route has a manually configured administrative distance greater than that of the primary route and therefore would not be in the routing table until the primary route fails.
In this question, the floating static route to subnet 209.165.200.224/27 is manually assigned the AD of 254.
can you plz explain qestion 2
any one plz explain
qestion 2
@Haji gu: The subnet 10.10.1.20/30 covers the destination 10.10.1.22 as this subnet ranges from 10.10.1.20 to 10.10.1.24 so it is the correct answer.
How can I view the questions. All I can see are the explanations. Thank you for the reply.
Can someone please explain question 11, how do you recognise a static route to R1 and where is the AD defined?
Question 2 in the explanation “the network this subnet ranges from 10.10.1.20 to 10.10.1.24 so it is the correct answer” / the network ranges from 10.10.1.20 to 10.10.1.23 it jumps in 4 steps.
can someone explain question 4 to me.
what do we mean by the longest prefix /27?
WHY?
Question 2
10.10.1.20 to 10.10.1.23 so it is the correct answer.
please explain Q4. Why AD is not used and why longer prefix rule is right answer?
@ashu: We have just added explanation for Q4 so please check again.
@9tut how can I contact you? Please write your email
slight typo on question 2 explanation that may cause confusion
10.10.1.24 would be the subnet ID for the following subnet, so the subnet range would be 10.10.1.20 – 10.10.1.23, and NOT 10.10.1.20 – 10.10.1.24. See below..
10.10.1.0 – 10.10.1.3 (using zero network)
10.10.1.4 – 10.10.1.7
10.10.1.8 – 10.10.1.11
10.10.1.12 – 10.10.1.15
10.10.1.16 – 10.10.1.19
10.10.1.20 – 10.10.1.23
10.10.1.24 – 10.10.1.27
@glorious_estefan: Thank you for your detection, we updated Q2 explanation.
Hi, Q1. A 10.0.0.1/32 (the /32)
Is this just used in the routing table? send anything starting with a 10.—- send out this way.
hi, everyone is talking about questions here, but i can not see them! am i from an other world ?
@vuhidus you must pay member fee in order to view ans
for Q9 The subnet 10.10.1.20/30 covers the destination 10.10.1.22 as this subnet ranges from 10.10.1.20 to 10.10.1.23 so it is the correct answer.
with subnet mask 255.255.255.252 252 which have 4 hosts start from 20 21 22 23 so it cover 10.10.1.22. its correct ans C
A. ip route 10.10.1.0 255.255.255.240 10.10.255.1 NOT qualify because subnet 240 only have 16 hosts if strat from given 10.10.1.0 then max will be 10.10.1.15
B. ip route 10.10.1.16 255.255.255.252 10.10.255.1 subnet 252 only got 4 hosts
D. ip route 10.10.1.20 255.255.255.254 10.10.255.1 subnet only got 2 hosts
for Q9 is that base on long prefix match?
For this question (question 9):
A packet is sent through router R1 to host 172.16.3.14. What destination does the router send the packet to?
The correct answer should be D:
D. 207.165.200.250 via Serial0 / 0/0
As the static has a Static Route Administrative Distance is 1 compared to OSPF which has 110
Could anyone explain to me why C?
For this question (question 9):
A packet is sent through router R1 to host 172.16.3.14. What destination does the router send the packet to?
I found this article:
https://packetlife.net/blog/2010/aug/16/route-preference/
A router evaluates routes in the following order:
1 – Prefix Length – The longest-matching route is preferred first. Prefix length trumps all other route attributes.
2 – Administrative Distance – In the event there are multiple routes to a destination with the same prefix length, the route learned by the protocol with the lowest administrative distance is preferred.
3 – Metric – In the event there are multiple routes learned by the same protocol with same prefix length, the route with the lowest metric is preferred. (If two or more of these routes have equal metrics, load balancing across them may occur).
So then what is correct answer to Q9? C or D?