Exam 300-410 topic 1 question 256 discussion

Correct: B - Both static routes must have a separate Track object and IP SLA probe. C - Each SLA probe must originate from a different ISP, therefore a different IP address. Wrong: A - Only a separate Track object won't help with anything, we need also a separate IP SLA probe. D - This is redundant, the router knows which interface to use for both next hops (based on ARP and MAC address table). E - This is just messy and not needed, we just need to set a different source for each probe (answer C).

Maybe someone get confused about this cause they are seeing the community post. But there is a why they use the /32 route: "The first two static routes are there to make sure that the tested IP address inside the ISP1 is truly reached only via link to ISP1, and if that link is down, then the pings are going to be thrown away (this is to prevent pinging 8.8.8.8 via ISP2 thanks to the default route)." The key point is that they want that only ISP1 is going to reach 8.8.8.8 so we want that if that specific route is not reachable they will fallback to the second default route but they will no be able to contact 8.8.8.8 cause there is a null0 route because this is on purpose

A -> No, separate probes and track objects for each static route B -> Correct C -> Correct, if we configured the probe as: icmp-echo 8.8.8.8 source-ip <RoutersWANaddress> D -> No, including the egress interface is redundant E -> No, there is nothing wrong with the current static routes besides the attached track objects

im going with B & C

Im going for B and C, because the alternative E it's isn't needed, with the default route u already have communication with google DNS, so you only need to separate the tracks between static routes and WAN's

It is not clearly described what they want to configure with "E". It could be a valid option with the correct configuration. Based on this: https://community.cisco.com/t5/routing/ip-sla-tracking-a-far-ip/td-p/1971337 The first two static routes are there to make sure that the tested IP address inside the ISP1 is truly reached only via link to ISP1, and if that link is down, then the pings are going to be thrown away (this is to prevent pinging 8.8.8.8 via ISP2 thanks to the default route). ip route 8.8.8.8 255.255.255.255 Ethernet0/0 10.0.0.1 ip route 8.8.8.8 255.255.255.255 Null0 2 ip sla 1 icmp-echo 8.8.8.8 source-interface Ethernet0/0 threshold 800 timeout 1000 frequency 30 ip sla schedule 1 start-time now life forever track 1 rtr 1 reachability ip route 0.0.0.0 0.0.0.0 10.0.0.1 track 1 ip route 0.0.0.0 0.0.0.0 20.0.0.1 2

D & E are correct

I would vote for B and C. Setting the static route to 8.8.8.8 for both ISP doesn't make sense. It would make sense if it is only one static route for that.

https://community.cisco.com/t5/routing/ip-sla-tracking-a-far-ip/td-p/1971337