Q68Network AssuranceMultiple answers
Refer to the exhibit. What are two causes of IP SLA tracking failure? (Choose two.)
Select 2 answers.
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Community votes
Discussion · 20
16
Another awful question. But it's realistic. It's realistic because poor communication skills are so common in this field.
8
I labbed this up in CML. Only E) is correct. No second matching answer so far.
A. The threshold value is wrong.
=> Threshold is correct, I tested it + see my previous post below. (frequency seconds ) > (timeout milliseconds ) > (threshold milliseconds )
B. The destination must be 172.30.30.2 for icmp-echo.
=> "icmp-echo 172.20.20.2" is correct, no changes are needed.
C. The default route has the wrong next hop IP address.
=> If you have a default route, and also the same default route with tracking, then you can delete the normal default route ("ip route 0.0.0.0 0.0.0.0 172.20.20.2"), and the other default route with tracking won't be affected ("ip route 0.0.0.0 0.0.0.0 172.20.20.2 track 10"). It stays in the configuration. So, the default route configuration looks fine.
D. A route back to the R1 LAN network is missing in R2
=> It is not required to have reachibility from R2 to R1's LAN for IP SLA and tracking to work. IP SLA + track works fine without it, it won't trigger a failure.
E. The source-interface is configured incorrectly.
=> That is true. Based on the picture it should be "icmp-echo 172.20.20.2 source-interface fa1/0".
6
lmao, true
D, E 5
Selected Answer: DE
A, B and C are all wrong.
Idk why you voted A as a correct answer, because setting a threshold of 500 ms is perfectly valid. You are basically saying 'if the ICMP-echo reply comes after 500 ms, then remove the route'.
B and C are wrong because the default routes and ADs are configured correctly for what the track and SLA configs are trying to do.
D and E are technically correct, but they exclude each other:
- If you use fa0/0 then the ISP probably needs a route to the internal network, which makes D correct. But if D is true then E is incorrect, because if the ISP has a route to the internally network, then it has reachability back to FA0/0 and the source-interface is not configured incorrectly anymore, so E is wrong.
- If E is correct, then the ISP no longer needs a route to the internal network, which makes D wrong.
4
Threshold is fine.
(frequency seconds ) > (timeout milliseconds ) > (threshold milliseconds )
(frequency 10 seconds = 10000ms ) > (timeout 5000ms ) > (threshold 500ms)
https://notes.networklessons.com/ip-sla-parameters
D, E 3
Selected Answer: DE
Fa0/0 is probably hidden from R2, so also R2 won't have routing to reach it.
3
I'll say D and E
A. The threshold value is wrong
- Not wrong. Works on routers.
B. The destination must be 172.30.30.2 for icmp-echo.
- It could be either of the two ISP's
C. The default route has the wrong next hop IP address.
- The command "no ip route 0.0.0.0 0.0.0.0 172.20.20.2" will not remove "ip route 0.0.0.0 0.0.0.0 172.20.20.2 track 10" if it exists on the router. And if it does not exist, it will throw this error: "%No matching route to delete"
D. A route back to the R1 LAN network is missing in R2.
- R1 LAN is the source interface. Ideally, the IP SLA source-interface should be the interface facing the ISP (except in cases of BGP redistribution).
E. The source-interface is configured incorrectly.
- Now this means almost the same thing as option D, but since we've been told to choose two options, we have to pick it as well.
C, E 3
Selected Answer: CE
It is CE.
3
It's CE, if you delete the default route to 172.20.20.2 obviously the tracking won't work, and the source interface is clearly wrong.
D, E 3
Selected Answer: DE
Since it's using Source-interface Fa0/0 we can assume R2 will not have a route back to it, so to solve the issue, change the source-interface to Fa1/0.
A, E 2
Selected Answer: AE
A and E
D. I don't think so. The ISP is probably not interested in my LAN IP range, especially when it is private range. So with E (another source interface) it is not necessary to go for D
2
Correction: LAB test threshold=500ms, SLA works normally. Answer: DE is ok
D, E 2
Selected Answer: DE
Guys it´s D and E
Just check the SAME question here Question #253 <- to get the answer
D, E 2
Selected Answer: DE
D and E are correct
2
A. Threshold seems fine
B. Why would we be tracking the secondary link with IP SLA
C. Might be the issue
My understanding is that ip route 0.0.0.0 0.0.0.0 172.20.20.2 track 10 will only get installed when track is up. Track will go up only when 172.20.20.2 is reachable and i believe it is not since our default route is pointing to 172.30.30.2 (ad 5 - is installed since tracked default is unreachable)
no ip route command will not remove static route with track statement
D. No proof of that but real case scenario
E - We can source the echo from any interface
I would go with C & D
1
Actually D and E contradict each other
One of them has to be present
1
Actually Q253 is different but you can still get some information from it.
A. Threshold is OK since it was OK in Q253 so not one of the two answers
B. Destination should not be 172.30.30.2 for icmp-echo so not one of the 2 answers
C. Both default routes are OK (the No removes any previous untracked default route through 172.20.20.2 so not one of the two answers
Clearly E is an answer, should not be using LAN IP as SLA source (this was a possible answer in Q253 but the SLA source interface there was Fa1/0 so wasn't the answer there)
But if you are using LAN IP as SLA source, and R2 needs a route back to it and likely does not and D is the only answer we have left to correctly choose.
A, D 1
Selected Answer: AD
I think the E is not correct because there is no issue with Fa0/0 as the source interface, since we want to check the ping from the LAN interface, so that rules out B and C, leaving only A because we are using "Reachability" tracking, so the threshold value is not important and can be ignored
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/17-5/configuration_guide/ip/b_175_ip_9500_cg/configuring_enhanced___object_tracking.pdf page 3
A, E 1
Selected Answer: AE
A & E. Threshold value is wrong, source should be reachable by ICMP, so the route on R2 is not going to help
D, E 1
Selected Answer: DE
it is D & E :
since this is connected to the internet, it will use NAT.
So the source interface is wrong and as I said (to internet) there is no route for LAN on ISP