This post continues the EVPN-VXLAN lab from the previous one.

For now I configured the simplest possible variant of RT assignment – one vrf-target for all ES and VNI routes (vrf-target target:65000:1):

Let’s check some EVPN routes:

Notice that all routes have RT target:65000:1 (except type 4 routes, that has special RT assignment policy).
Effectively this means that all PE routers, participating in this EVPN instance, will learn all routes from all VLANs/VXLANs.

If you need to alter this behaviour, you can configure per-VNI route target assignment for specific VNI (note that this RT applies only to EVPN type-2 and type-3 routes):

But unfortunately that’s not all. After applying this configuration, routes for VNI 100 are advertised with new RT:

But routes for VNI 100 are not recieved on the other side:

And of course connectivity for VNI 100 breaks.

If you familiar with MPLS L3VPN, you should already spot the problem: RT configuration in VNI-options stanza configures only export RT, but doesn’t create corresponding vrf-import policies. So you need to configure it manually:

Notice that you need to permit not only RT for this specific VNI, but also general vrf-target RT, used for EVPN type 1 routes.

After applying this config vMX starts to import routes for both VNI:

And connectivity for VNI 100 restored.

So this option works, but requires manual vrf-import policy configuration.

There is another, more simple option for RT assignment – auto-RT:

Routes on vMX after appying this config:

Notice RT for VNI 200 route – this RT is autoderived from device AS number (configured in routing options stanza) and VNI ID.

There is no need to manually configure vrf-import policies in this case – this policies configured and applied automatically:

Notice that this policy allows to import Auto-RT for both VNI, but for VNI 100 this is not used because we manually configured static RT for this VNI in vni-options stanza. This configuration creates another hidden policy:

So, that’s it. Not so complex after all.

Remember 3 simple rules:
– General vrf-target statement (under switch-options in QFX case and under routing-instance in MX) used for EVPN routes type 1. This RT will be used for all EVPN route-types if you don’t configure anything else.
– vrf-target auto allow you to use different autoderived per-VNI RT for EVPN type 2 and 3 routes (pay attention to AS number configured under routing options stanza – auto-RT use this number).
– protocols evpn vni-options allows you to manually configure RT for specific VNI – you can choose any VNI-to-RT mapping you want. But this configuration apply RT only for vrf-export – you need to manually define and apply vrf-import policies. Also don’t forget to include general RT in this policy.