Exam 300-410 topic 1 question 41 discussion

Actual exam question from Cisco's 300-410

Question #: 41
Topic #: 1

Refer to the exhibit. Routing protocols are mutually redistributed on R3 and R1. Users report intermittent connectivity to services hosted on the 10.1.1.0/24 prefix.
Significant routing update changes are noticed on R3 when the show ip route profile command is run.
How must the services be stabilized?

A. The routing loop must be fixed by reducing the admin distance of OSPF from 110 to 80 on R3
B. The routing loop must be fixed by reducing the admin distance of iBGP from 200 to 100 on R3
C. The issue with using BGP must be resolved by using another protocol and redistributing it into EIGRP on R3
D. The issue with using iBGP must be fixed by running eBGP between R3 and R4

Show Suggested Answer

Suggested Answer: B 🗳️

by AliMo123 at Nov. 3, 2021, 2:04 p.m.

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AliMo123

Highly Voted 3 years, 9 months ago

B is correct After redistribution, R3 learns about network 10.1.1.0/24 via two paths:+ Internal BGP (IBGP): advertised from R4 with AD of 200 (and metric of 0)+ OSPF: advertised from R1 with AD of 110 (O E2) (and metric of 20)Therefore R3 will choose the path with the lower AD via OSPF But this is a looped path which is received from R3 -> R2 -> R1 -> R3. So when the advertised route from R4 is expired, the looped path is also expired soon and R3 willreinstall the main path from R4. This is the cause of intermittent connectivity.In order to solve this issue, we can lower the AD of iBGP to a value which is lower than 110 so that it is preferred over OSPF-advertised route.

upvoted 21 times

wts

3 years, 6 months ago

Routing protocols are mutually redistributed on R3 and R1. R3 learns about network 10.1.1.0/24 via three paths: OSPF(110[O E2]), EIGRP(170[D EX]), iBGP(200). The IBGP has too much administrative distance. Packets with a destination address from the 10.1.1.0/24 subnet miss this path and travel in a circle. C and D are too strange options. Reducing the administrative distance makes the routes of this protocol more preferable. 10.1.1.0/24 is behind the BGP, hence option B.

upvoted 2 times

Jenia1

3 years, 5 months ago

B should be correct, C is general and we have more specific options. D would be correct if they mentioned public AS/IP, but u can see private on the exhibit

upvoted 2 times

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[Removed]

Most Recent 1 year, 11 months ago

Selected Answer: B

This is one lazy looking diagram.

upvoted 4 times

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Malasxd

2 years, 2 months ago

Selected Answer: B

B is correct

upvoted 2 times

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