Refer to the exhibit. An engineer must configure OSPF with R9 and R10 and configure redistribution between OSPF and RIP, causing a routing loop. Which configuration on R9 and R10 meets this objective?
A.
router ospf 1 redistribute rip subnets tag 20 ! route-map deny_tag20 deny 10 match tag 20 route-map deny_tag20 permit 20 ! router ospf 1 distribute-list route-map deny_tag20 in
B.
router ospf 1 redistribute rip subnets tag 20 ! route-map deny_tag20 deny 10 match tag 20 route-map deny_tag20 deny 20 ! router ospf 1 distribute-list route-map deny_tag20 in
C.
router ospf 1 redistribute rip subnets tag 20 ! route-map deny_tag20 deny 10 match tag 20 route-map deny_tag20 permit 20 ! router rip 1 distribute-list route-map deny _tag20 in
D.
router ospf 1 redistribute rip subnets tag 20 ! route-map deny_tag20 permit 10 match tag 20 route-map deny_tag20 permit 20 ! router ospf 1 distribute-list route-map deny_tag20 in
If the objective is to create a loop, i choose D and C because both of them permit subnet with tag 20 into OSPF.
If the objctif is avoid a loop, so i choose A
Funny how the omission of a single word can completely change the objective of a sentence
Question:
Refer to the exhibit. An engineer must configure OSPF with R9 and R10 and configure redistribution between OSPF and RIP "without" causing a routing loop. Which configuration on R9 and R10 meets this objective?
Have they erroneously omitted the word "without"? - right answer is A
Have they intentionally omitted the word "without"? - right answer is D
I am just going to chalk this one up to another one of their stupid questions, sometimes they make them because of errors and sometimes they make them trying to intentionally mislead
"without" --> right answer is C. in A OSPF has a distribute list for the tags after redistributing into OSPF. This may or may not solve suboptimal routing, but it won't solve a loop. C solves the loop.
the description is: "someone MUST configure redistribution and causing a routing loop"
the question is: "which configuration meet this objective"
you are going to select the answer to CAUSE a loop, rather than AVOID a loop
Sobre, i said , if I avoid a loop is the opción A, and if I create a loop the opción is D. For this quesitos is D. Because the question is explicit create a loop for wrong the engineer
team aswer correct is A:
It has to be in the OSPF domain when we deny the prefix to block upstream in the OSPF domain and avoid the loop (remember that ospf has an AD of 110 and RIP of 120) and the routers prefer a lower AD for OSPF even though they have the downstream network. and a loop is generated. Deny traffic on the destination router in OSPF. because the route is received by external OSPF with a distance AD 110
There is no doubt about that right answer is A - just labbed it.
When you are redistributing from RIP into OSPF, it is redistribution from higher AD (RIP=120) to lower AD (OSPF=110).
R10 receives routes from R11 (RIP routes) -> redistributes it into OPSF to R6 -> R5 -> R9.
At the beginning, R9 see routes from R11 too (RIP routes). When R9 receives that redistributed routes via OSPF, populates its routing table with this routes because OSPF AD (lower than RIP AD) -> this also can happen vice versa on R10 = routing loop.
To break routing loop, you have to filter routes redistributed from RIP to OSPF -> tagg them and do filtering based on tag on both R10 and R9 routers.
You are wrong. It blocks it from getting into the RIB of the R9 and R10, therefore R9 and R10 choose RIP route. The answer is A or D. Answer C stops the tag routes from getting back into the RIP AS. However router R9 and R10 still have OSPF E2 route if we choose option C.
The distribute-list in "A" causes the redistributed rip routes (tagged 20) blocked from getting into RIB from ospf LSDB table on the specific device where the distribute list is applied. For example, let's see what happens if we apply it on R9:
The route 11.11.11.11 (from below example) is still there in ospf LSDB, and gets advertised to the other ospf routers as lsa type 5.
See more info on the topic:
https://networklessons.com/ospf/ospf-distribute-list-filtering
r9#show ip ospf database | b External
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
1.1.11.0 1.1.61.10 1463 0x80000002 0x00C272 20
1.1.19.0 1.1.61.10 1463 0x80000002 0x006AC2 20
1.1.19.0 1.1.91.9 1442 0x80000002 0x009D72 20
1.1.91.0 1.1.91.9 1442 0x80000002 0x008245 20
11.11.11.11 1.1.91.9 983 0x80000001 0x008E6B 20
r9#
I tend to agree here, the option A would prevent R9 & R10 to redistribute the tagged OSPF (LSA type 5) routes back to RIP. The fact that the routes still in the OSPF LSDB should not be an issue. So my best option is go with A. I will lab this one later.
r9(config-router)#do sh ip route | b Gateway
Gateway of last resort is not set
1.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O E2 1.1.11.0/24 [110/20] via 1.1.59.5, 00:00:31, GigabitEthernet0/0
C 1.1.19.0/24 is directly connected, GigabitEthernet0/3
L 1.1.19.9/32 is directly connected, GigabitEthernet0/3
C 1.1.59.0/24 is directly connected, GigabitEthernet0/0
L 1.1.59.9/32 is directly connected, GigabitEthernet0/0
O 1.1.61.0/24 [110/3] via 1.1.59.5, 00:00:31, GigabitEthernet0/0
O 1.1.65.0/24 [110/2] via 1.1.59.5, 00:00:31, GigabitEthernet0/0
C 1.1.91.0/24 is directly connected, GigabitEthernet0/2
L 1.1.91.9/32 is directly connected, GigabitEthernet0/2
11.0.0.0/32 is subnetted, 1 subnets
O E2 11.11.11.11 [110/20] via 1.1.59.5, 00:00:31, GigabitEthernet0/0
=> Injected rip routes by redistribution appear as O E2 routes in routing table.
Poorly written question as always, if you read the question it says the engineer must configure redistribution but it caused a routing loop, I don't think they are wanting us to create a routing loop because they are always teaching how to prevent it.
I agree, probably the question is wrong. Typovy already pointed out that the correct answer would be "C" to avoid the loop. Surprisingly, the question instructs to create a loop, which can be achieved by answer "D".
When I tested the configurations in CML, I had a problem with solution "C". Unlike ospf, rip does not have the parameter route-map when using distribution- lists.
R10(config)#router rip
R10(config-router)#distribute-list ?
<1-199> IP access list number
<1300-2699> IP expanded access list number
WORD Access-list name
gateway Filtering incoming updates based on gateway
prefix Filter prefixes in routing updates
Instead, I needed to choose a classic configuration with redistribution and route-map to match and deny the tagged routes (rip routes coming back from ospf):
R10(config)#router rip
R10(config-router)#redistribute ospf 1 route-map MATCH metric 3
objective is to create a loop... like you are testing an interviewer...
upvoted 1 times
...
...
This section is not available anymore. Please use the main Exam Page.300-410 Exam Questions
Log in to ExamTopics
Sign in:
Community vote distribution
A (35%)
C (25%)
B (20%)
Other
Most Voted
A voting comment increases the vote count for the chosen answer by one.
Upvoting a comment with a selected answer will also increase the vote count towards that answer by one.
So if you see a comment that you already agree with, you can upvote it instead of posting a new comment.
Typovy
Highly Voted 2 years agojabal93
8 months, 2 weeks agojabal93
8 months, 2 weeks agoyasmiine
Most Recent 1 week, 1 day agoCiscoTerminator
2 months agoCiscoTerminator
2 months, 3 weeks ago26307ae
9 months ago[Removed]
9 months ago[Removed]
1 year, 3 months agofizzer
1 year, 7 months agobk989
8 months, 1 week agochris110
1 year, 7 months agoyellowswan
1 year, 7 months agoMuste
1 year, 8 months agochaocheng
1 year, 8 months agointeldarvid
1 year, 9 months agointeldarvid
1 year, 9 months agointeldarvid
1 year, 9 months agodaloslav
1 year, 11 months agoHungarianDish_111
1 year, 11 months agobk989
9 months, 1 week agoHungarianDish_111
1 year, 10 months agoHungarianDish_111
1 year, 10 months agoioreskovic
1 year, 10 months agoPietjeplukgeluk
1 year, 3 months agoHungarianDish_111
1 year, 10 months agoHungarianDish_111
1 year, 10 months agoHungarianDish_111
1 year, 10 months agoHungarianDish_111
1 year, 10 months agoGReddy2323
1 year, 11 months agoHungarianDish_111
1 year, 11 months agoHungarianDish_111
1 year, 11 months agoJoeyT
1 year, 10 months ago