Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
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Figure 53 Fabric Extend IP Mode (VXLAN / IPsec) MTU Considerations
Tip
WAN providers will typically use MPLS to deliver their WAN services. MPLS equipment is
perfectly capable to handle oversize frames in excess of 1600 bytes. However, the WAN
provider may choose whether or not to allow larger MTUs in their service offerings.
For Data Center Interconnect (DCI), it is also possible to deploy Fabric Extend with jumbo frame sizes. The
same encapsulation overheads of 22 (Mac-in-Mac) + 50 VXLAN) bytes apply, but the original Ethernet
frame generated by servers/VMs will now have an IP MTU of 9000 bytes, which will result in a maximum
Fabric Extend frame size just short of 9100 bytes. Again, the WAN provider must be able to offer a jumbo
capable service to meet these MTU requirements.
Tip
When using jumbo frame sizes, the IP MTU is set (on the end-stations) to 9000 bytes,
resulting in a maximum Ethernet frame size that is well below the absolute maximum that
jumbo capable equipment can support (typically between the 9200 – 9800 mark).
Extreme VSP platforms can handle maximum frame sizes of up to 9600 bytes.
A special case to consider is using Fabric Extend over the Internet (as opposed to a WAN). The Internet will
not handle any traffic with an IP MTU greater than 1500 bytes so, at first sight, this would not be an option
for Fabric Extend (or the VXLAN Gateway approach). The only way to run Fabric Extend over the Internet
(or a WAN where IP MTUs greater than 1500 are not allowed) is for the Fabric Extend terminating
equipment to support IP fragmentation and re-assembly. Extreme Networks offer this capability on the
Fabric Connect VPN XA 1400 platforms and the VSP4450/4850 platforms (latter must be associated with
an Open Network Adapter - ONA).