The same considerations for ES and AD routes, and DF election apply for all-active multihoming as for single-active multihoming; the difference is in the behavior on the NDF DCGW. The NDF for a specified service performs the following tasks:
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From a data path perspective, the NDF blocks ingress and egress paths for broadcast and multicast traffic on the VXLAN instance bindings associated with the I-ES, while unknown and known unicast traffic is still allowed. The unknown unicast traffic is transmitted on the NDF if there is no risk of duplication. For example, unknown unicast packets are transmitted on the NDF if they do not have an ESI label, do not have an EVPN BUM label, and they pass a MAC SA suppression. In the example in Figure: All-active multihoming and unknown unicast on the NDF, the NDF transmits unknown unicast traffic. Regardless of whether DCGW1 is a DF or NDF, it accepts the unknown unicast packets and floods to local SAPs and EVPN destinations. When sending to DGW2, the router sends the ESI label identifying the I-ES. Because of the ESI-label suppression, DCGW2 does not send unknown traffic back to the DC.
Figure: All-active multihoming and unknown unicast on the NDF
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The MAC/IP routes and the FDB process
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MAC/IP routes associated with the VXLAN instance are advertised normally.
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MACs are installed as normal in the FDB for received MAC/IP routes associated with the VXLAN instance.
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The IMET routes process
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As with single-active multihoming, IMET-AR-R routes must be withdrawn on the NDF (MhStandby state). Only the DF advertises the IMET-AR-R routes.
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The IMET-IR advertisements in the case of the NDF (or MhStandby) are controlled by the command config>service>vpls>bgp-evpn>vxlan [no] send-imet-ir-on-ndf, as in single-active multihoming.
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The behavior on the non-DF for BUM traffic can also be controlled by the command config>service>vpls>vxlan>rx-discard-on-ndf {bm | bum | none}, where the default option is bm. However, the user can change this option to discard all BUM traffic, or forward all BUM traffic (none).
The I-ES DF PE for the service continues advertising IMET and MAC/IP routes for the associated VXLAN instance as usual. When the DF DCGW receives BUM traffic, it sends the traffic with the egress ESI label if needed.