Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
© 2019 Extreme Networks, Inc. All rights reserved. 115
Figure 62 Extending an L2 VSN Across Fabrics with VXLAN Gateway
Figure 62 shows a possible use of VXLAN Gateway to extend a Fabric L2 VSN across two separate Extreme
SPB Fabrics where the VTEPs are Extreme VSP platforms at both ends. The L2 VSN L2 I-SIDs are mapped
to the VXLAN VNI on the VXLAN Gateways so the I-SID value can be different at both ends. The VXLAN
cloud is by definition an IP overlay and can be transported over any L3 capable transport network including
a WAN cloud but on condition that this is capable of handling oversize frames.
Note
The VXLAN encapsulation adds 50 bytes to the maximum size of an Ethernet packet, 1518
(untagged) or 1522 (tagged). The Extreme Networks VXLAN Gateway functionality only
encapsulates in VXLAN the native Ethernet frame and does not include the SPB Fabric
Mac-in-Mac encapsulation.
Caution
The VXLAN Gateway functionality is only supported on Extreme Networks VSP 4900,
7200, 7400, 8200, and 8400 platforms, and these platforms do not support IP
fragmentation of VXLAN frames. The VXLAN underlay network must therefore be able to
support oversized or jumbo frames sizes. It is not possible to run VXLAN Gateway over the
Internet as that would require IP fragmentation.
It should be noted running IP multicast on the resulting end-to-end L2 segment will present challenges. The
Fabric L2 VSNs can be IP Multicast enabled, but no IGMP Sender or Receiver information will be exchanged
on the VXLAN VNI segment. IGMP static entries would thus need to be provisioned in order to always flood
the required IP Multicast streams across the VXLAN cloud. The other alternative is not to IP Multicast enable
the Fabric L2 VSNs, which will result in all IP Multicast traffic to be treated like L2 multicast and be flooded
everywhere. Both approaches will be handled using inefficient ingress replication on the VXLAN overlay.
Tip
Prefer a Fabric Extend approach if there is a requirement for IP Multicast.
Figure 63 shows the use of the same VXLAN Gateways and VXLAN interconnecting cloud to interconnect
an L3 VSN service between the same Extreme SPB Fabrics. This approach essentially simply defines an L2
segment over the VXLAN overlay alone and places IP interfaces on this segment at both ends on the
VXLAN Gateways. Those IP interfaces can belong to a VRF, and thus to an L3 VSN, and can be used to
exchange IP routes for the interconnecting VRFs using a conventional IP or IPv6 routing protocol (RIP,
OSPF, BGP). On the VXLAN Gateway, the VXLAN VNI is still mapped to a Fabric L2 I-SID, which in this case
is used to simply map to a local CVLAN on the same node where the routing IP interface resides.