Network & Infrastructure / EVPN, VXLAN & Data Center Fabrics
EVPN border-leaf redistribution and unintended tenant transit
A border leaf imports external routes into a tenant, then accidentally re-exports another tenant's learned prefixes. The resulting connectivity violates the intended shared-services boundary.
Environment and inputs: BGP EVPN overlays on a routed underlay; supported route types and multihoming behavior depend on the network OS. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Trace route targets, VRF import/export policy, external redistribution and route origin tags on each border. Test the exact forbidden prefix alongside the required shared-service prefix.
Explain the result
A border combines several policy domains. Permissive redistribution can transform route visibility intended for one service into transitive reachability between otherwise isolated tenants.
Plan the fix
Define explicit permitted prefixes and origin handling at every redistribution boundary. Keep shared services in a reviewed routing model rather than relying on broad reciprocal route-target imports.
Check the result and rollback
Validate positive and negative reachability tests through both redundant borders and during failure. Restore the previous policy immediately if cross-tenant routes become visible or isolation tests fail.