ECMS Practice Question - Feb 5th

[rmarta]

ECMS Question

Refer to the exhibit. Assume that the MX in question is a spoke connected via AutoVPN to one hub using split tunnels, all its local subnets have been advertised over the VPN, and both its WAN connections are up. How will the MX route traffic sourced from subnet 172.17.25.0/24 destined for the internet?

1. It will be sent out WAN1 as long as it is up.
2. It will be sent out WAN2 as long as it is up.
3. It will be sent out WAN1 as long as it meets the thresholds in the performance class called “Telepresence”.
4. It will be sent out WAN2 as long as it meets the thresholds in the performance class called “Telepresence”.
5. It will be load balanced between WAN1 and WAN2.

[CMR]

I'm going for Lando Norris

[Philip D'Ath]

Another good question!

Spoiler

D.

[ww^]

E

[Karsten Iwen]

Spoiler

First we have to find out the relevant information:
- AutoVPN is in use, but uses SplitTunnel
- It is traffic to the internet

- Load balancing is enabled
- The only flow-Preference for the source is the last one for 9.9.9.9/32. Although it is an address on the internet, it's not "the internet".

It is not a) or b) as we have load balancing enabled but no flow preference matches

It is not c) or d) as it is no AutoVPN-traffic

The answer should be "e".

[CMR]

@Karsten Iwen indeed, I missed the split tunnels part, so Sebastian Vettel it is...

[Raphael_L]

I'm not getting those F1 references . But I would go with

Spoiler

D

[CMR]

@Raphletourn

[Raphael_L]

oh god... I feel ashamed ...

Now I get it 🙂

[CMR]

🤣just my odd sense of humour! 😇

[ECMS-550-220]

C . It will be sent out WAN1 as long as it meets the thresholds in the performance class called “Telepresence”.

will prefer WAN2 if telepresence performance cross threshold

E may be incorrect As it said load balanced with WAN1 & WAN2 but flow preference marked for WAN1

[bryand2]

It's D.

[BRUCE NEWTON]

Can't wait to see the Meraki answer to this one. In my opinion it should be E.

The key factors are that the AutoVPN is split tunnel and that it is internet traffic.

Being internet traffic with a split tunnel the traffic is not impacted by the SD-WAN policies.

Since there is no Internet Flow Preference for the source address/subnet, and assuming its not going to host 9.9.9.9, then the traffic will be load-balanced out of WAN1 and WAN2 as this is the default routing if no other preferences apply.

Well, that's my theory anyway.....

[rmarta · Accepted solution]

After all the conversations that were had in this chat, I am happy to announce that the correct answer is...

🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁🥁

E! Traffic coming from that subnet bound to the internet will leave through the local breakout (split tunnel), and since there is no specific flow preference for that subnet, it will be load balanced!

Thanks for tuning in. We're soon coming back with another question!