ECMP vs VRRP?

[Chris_Chance]

We are looking at reworking our layout to start growing to have full redundancy.

MLAG between 2x aggregation x670's Feeding each remote site with 1x 10gigabit uplink. We're good on that simple.

MLAG between our L3 Extremes we plan to use for L3 Routing. Those will connect via standard lag to both of the above aggregation switches. Still good here simple LAG+MLAG's.

Now we reach the L3 portion. Hanging off of those L3 Extremes we have our BRAS/PPPoE Boxes, that are connected on their backend via a LAG to both of the aggregation 670's.

We bring up a VLAN to each of the L3 Extremes with a /30(or/31 whatever), But we want to make sure if one of our L3 x670's die that we have complete redundancy.

Simplest idea is just Enable VRRP, but i REALLY hate the idea of waisted tech resources, and the idea that 1 box is just sitting their idle urks me. So I thought Hey Why not just use OSPF ECMP to solve the issue.

And that led me to the question why ever use VRRP if ECMP exists? Where does the drawback exist that i'm missing to using OSPF ECMP? I get connection based load balancing between the main 2 routers, and failover protection if one fails.

We already plan to use OSPF on the BRAS's to deliver customer /32's based on radius so that we have no waisted IPv4 (as we won't be dedicating subnets to specific servers that might not use them all)

So the comparison

BRAS -> LAG to 2-x670's -> VRRP
vs
BRAS -> VLAN to 2 ports of the BRAS to 2-x670 on a /30 each - > OSPF ECMP

[Jeremy_Homan]

Is this the suggested way to setup VRRP? Thanks for answering all my questions!

[Bill_Stritzinge]

Jeremy,

The virtual IP is then broadcast down both links - in your case all you have to do is create the .pol file and then apply to the ISC link, your will see both VRRP sides go MSTR - and then you will see both links go active, there is no additional configuration necessary.

Bill

[Jeremy_Homan]

We're running 15.3.4.6 w/ latest patch.

How does this work given that they share the same logical IP? IE; 1.1.1.1?

For my deployment, I had 10 vlans. I put 5 on VRID1, and 5 on VRID2. I made switch 1 master for all VRID1 sessions, and switch 2 master for all VRID2.

Is your method better?

Thanks,

[Bill_Stritzinge]

Jeremy,

That is correct.. it is a way to make it active/active into your core. There are not any adverse issues in doing so. We have done it a ton... The only caveat would be to make sure you are using 15.3 or later (older code works, but I would suggest that version and beyond).

Bill

[Jeremy_Homan]

Bill, this interests me. As of right now, I have 5 floors all coming down to my core via MLAG. The core is a pair of 460's. I'm utilizing VRRP at my core for L3 redundancy..

With what you're saying is that if I create that policy on one side of my core ISC channel, they won't be able to communicate with their VRRP talk and will bring up all instances of VRRP as active?

Will this pose any other problems? By doing this, both switches will be active forwarding packets?

Thanks,

Jeremy