Overlay Routing
Tenants may have multiple overlays across a data center network where different
VLANs belonging to the same tenant are mapped to different VXLAN Network Identifiers (VNIs).
Tenants require routing between the VLANs, and VXLAN gateway nodes would need to act as Layer 3
gateways that are capable of routing traffic between tenant VLANs. Inter-overlay routing involves
routing:
- Routing traffic from a tenant VLAN into a
tunnel with the destination overlay‘s VNI.
- Routing traffic from a tunnel to a tenant
VLAN that is different from the tenant VLAN associated with the VNI in the received packet‘s
VXLAN header.
- Routing traffic from a tunnel to the same or
different tunnel.
A VXLAN tunnel endpoint (VTEP) is designated as the gateway for an overlay by manually
configuring it or by running a first hop redundancy protocol (FHRP), such as
VRRP (Virtual Router Redundancy Protocol) on the tenant VLAN on the gateways and letting the protocol determine the
placement of the router. ARP is not learned by VXLAN tunnels when the destination MAC address is
the VRRP MAC address.
Note
Routing between a normal VLAN and a VXLAN tenant VLAN is not supported and both the VLANs
should be VXLAN tenant VLANs.
Note
When MLAG and VRRP is configured on the tenant VLAN, VRRP should be active-active mode
between the MLAG peers.
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