WAN HA in different remote devices?

[PiEich00]

Hi everyone!
Currently I have a regular WAN connection to 2 MPLS providers with HA using OSPF like image 1:

But I would like to move the 2nd MPLS to a remote location, and connect the switches with fiber like image 2:

Is it possible? How? The switches are C3850 with ipbase.

Thank you!

[Georg Pauwen]

Hello,

that is definitely possible. What are you running into ?

[PiEich00]

Nice to know it is possible!

Sorry I didn't get what you mean with that question...

[Joseph W. Doherty]

Is there a reason why you cannot run OSPF across the fiber link between your two 3850s?  Or, you can, but you have, perhaps, a load balancing issue?  Or, some other issue?

[PiEich00]

Aaah, got it!

No, in fact I haven't yet done it, because I wasn't sure that a regular OSPF config involving the fiber and the 2 interfaces in the separate devices would work as it is working in 1 device right now...

It seems is much simpler than I was thinking

[Joseph W. Doherty · Accepted solution]

For just HA, two routers are likely better than a single router, and either link could be used if the other fails.  Where you may see a difference, is load distribution across the two links.  With one router, you might be seeing about a 50/50 share.  With two routers, it's possible you might see one link not be used at all (excluding OSPF traffic or if the other links fails).  The latter situation might be considered both good or bad.  Good in that, assuming both links have same capacity, losing one means you lose no operational bandwidth loss, bad in that, with both active, you're only using half your available bandwidth.

[Joseph W. Doherty]

Oh, two other things to note.

First, if your 3850s only have IPBase, they may only have a "mini/stub" version of OSPF, so you might have issues using two of them, as OSPF neighbors.

Second, 3850s can stack.  So, you might consider stacking them, with one WAN link connected to each stack member.  This improves your HA, vs. one unit, (BTW the two stack members should be on separate power circuits, and/or one with UPS backup), and makes the dual unit stack, logically, operate as a single unit (i.e. a "mini/stub" version of OSPF may continue to be okay).

[PiEich00]

They will be separate for several hundred meters, in different branches. That’s the main idea and concern of the WAN HA.

[Joseph W. Doherty]

Okay, that's fine too.  Just be aware you may need the IPServices feature set for full OSPF support.