VXLAN and BGP EVPN Configuration Guide for Dell EMC SmartFabric OS10 Release 10.5.2

In a Clos leaf-spine topology, if you configure the leaf nodes (VTEPs) in separate ASNs, the system cannot use the route targets that are automatically generated using the auto-evi or route-target auto commands. The route target includes the ASN and the route targets derived on each of the leaf nodes differ from one another.

In such eBGP EVPN scenarios, use the disable-rt-asn command to automatically provision route targets in the leaf nodes. When you use this command, the export route-target has the ASN value set to 0 and ensures that identical route targets are generated on all the leaf nodes. The leaf VTEPs can import EVPN routes only based on VNI, even though the leaf VTEPs are on different ASNs.

This command is applicable when you use the auto-evi or route-target auto commands for EVIs, symmetric IRB VRFs, or both.

Note: You must manually configure the route target and set the ASN value to 0 in other vendor switches that do not support the disable-rt-asn feature.

OS10(config)# evpn 
OS10(config-evpn)# auto-evi
OS10(config-evpn)# disable-rt-asn

OS10(config)# evpn 
OS10(config-evpn)# disable-rt-asn
OS10(config-evpn)# evi 1001
OS10(config-evpn-evi-1001)# route-target auto
OS10(config-evpn)# vrf BLUE
OS10(config-evpn-vrf-BLUE)# vni 64001
OS10(config-evpn-vrf-BLUE)# route-target auto 
OS10(config-evpn-vrf-BLUE)#