Considerations For The Core Vrf; Issu Support - Cisco Nexus 7000 Series Configuration Manual

ISSU Support

• Spanning Tree Protocol (STP) domain

Considerations for the core VRF

The following are considerations for the configuration of the core VRF:
• On the VTEP device:
• Throughout the transport network:
ISSU Support
The following are the ISSU support details for VXLAN flood and learn deployment:
• Cisco Nexus 7000 Series switches running Cisco NX-OS Release 6.2.10 or 6.2.12.
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
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multicast group is the way to provide the optimal multicast forwarding. It is possible, however, to have
multiple VXLAN segments share a single IP multicast group in the core network. VXLAN can support
up to 16 million logical Layer 2 segments, using the 24-bit VNID field in the header. With one-to-one
mapping between VXLAN segments and IP multicast groups, an increase in the number of VXLAN
segments causes a parallel increase in the required multicast address space and the amount of forwarding
states on the core network devices. At some point, multicast scalability in the transport network can
become a concern. In this case, mapping multiple VXLAN segments to a single multicast group can
help conserve multicast control plane resources on the core devices and achieve the desired VXLAN
scalability. However, this mapping comes at the cost of suboptimal multicast forwarding. Packets
forwarded to the multicast group for one tenant are now sent to the VTEPs of other tenants that are
sharing the same multicast group. This causes inefficient utilization of multicast data plane resources.
Therefore, this solution is a trade-off between control plane scalability and data plane efficiency.
Despite the suboptimal multicast replication and forwarding, having multiple-tenant VXLAN networks
to share a multicast group does not bring any implications to the Layer 2 isolation between the tenant
networks. After receiving an encapsulated packet from the multicast group, a VTEP checks and validates
the VNID in the VXLAN header of the packet. The VTEP discards the packet if the VNID is unknown
to it. Only when the VNID matches one of the VTEP's local VXLAN VNIDs, does it forward the packet
to that VXLAN segment. Other tenant networks will not receive the packet. Thus, the segregation
between VXLAN segments is not compromised.
Ensure that the root of an STP domain local to the VXLAN fabric is a VTEP, or placed within the fabric.
The STP root should not be outside the VXLAN fabric (below the VTEPs) since it will lead to Layer 2
loops.
◦ Enable and configure IP multicast.
◦ Create and configure a loopback interface with a /32 IP address.
◦ Enable IP multicast on the loopback interface.
◦ Advertise the loopback interface/32 addresses through the routing protocol that runs in the transport
network.
◦ Enable IP multicast on the uplink outgoing physical interface.
◦ Enable and configure IP multicast.
Configuring VXLAN Flood and Learn