> Rob Foehl > Sent: Tuesday, November 12, 2019 3:19 AM > > Given a pair of EX uplinked to a pair of MX, with various downstream CE that > may be single devices or their own layer 2 topologies, as in this terrible > diagram: > > MX1 - MX2 > | / \ | > EX1 EX2 > \ / > CEs > > ...and a need to deliver various EVPN services to access ports on the EX, > which currently run a bunch of layer 3 toward the CE devices (sometimes > including VRRP across the CEs, or eBGP to them, or both): > > Are there any "good" options for running all-active toward the EX while also > moving existing layer 3 up to the MX, or am I stuck with single-active and > carving out IFLs for each use case? > No you can never have active-active setup on L2 -because of the fundamental limitation dictating that you can't have the one MAC address seen on two ports at the same time. In L3 I can have a two routes to a given prefix, each pointing via different interface, you can't have the same with MAC addresses unfortunately. This is due to conversational address learning and the absence of metric at L2.
So that's why we have all these elaborate tricks to make it look as close to active-active as possible while not breaking the fundamental rule. Hence there are several levels of how close you want to get, ME to EX active-active I think it should be possible if you convert the bit between MX-es and EX-es into L2 encapsulated in L3 or MPLS. Say you run VXLAN between the MX-es and EX-es. And then the bit between EX and CEs you can run MC-LAG (where one of the ports in the LAG would be active and one will be backup). adam _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp