201, vCenter

VSAN and vSphere 6.5…

There is a not so nice feature in vSphere 6.5 which makes VSAN explicitly dependent on vCenter. It is detailed in the release notes but easily overlooked… http://pubs.vmware.com/Release_Notes/en/vsan/66/vmware-virtual-san-66-release-notes.html

Fixed in the latest update of vSphere/vCenter, but just be aware of the following steps before bouncing vCenter for maintenance or upgrade…

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Making room for NSX… Deleting ESXi VIB’s

VIB’s are kernel modules which make up the various capabilities of the VMware vSphere ESXi hypervisor together with hardware device drivers. When building vSphere ESXi Servers, hardware vendors can assist by providing ISO images which include hardware monitoring VIB’s together with common storage and network driver VIB’s for their servers.

There is a limit to the size of the vSphere ESXi boot image location (bootbank) of around 250MB and unfortunately, some hardware vendor ISO images are filled with so many device drivers, there is no room for additional drivers. This can cause NSX host preparations to fail…

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NSX-V SpoofGuard via API

SpoofGuard is a feature of NSX that provides administrative control of IP and Mac address assignment for VM’s. The two benefits of Spoofguard are to (1) control virtual machine access to virtual network switches, and (2) protect against unauthorized IP address and MAC address changes by virtual machine OS administrators and users.

Like other capabilities of NSX, SpoofGuard administrative control can be accessed via the NSX API…

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Jumbo Frames and Network Virtualization Overlay Networks

In data networking, the standard Maximum Transmission Unit (MTU) for IP frames is 1500 Bytes. Jumbo Frames are MTU’s larger than 1500 Bytes although when we reference Jumbo Frames, we are normally referencing a Frame with an MTU of 9000 Bytes.

Network Virtualization and the addition of an overlay (encapsulation) networking technology (VXLAN, STT, GRE, Geneve) to the data center requires some consideration as to what MTU to use due to the overhead of overlay transport technologies.

VMware NSX using the overlay technology VXLAN requires an MTU of 100 bytes greater than the networks used for Virtual Machines – In a traditional data center using a 1500 byte MTU for virtual machines, this would require the use of a 1600 Byte MTU for the L2 or L3 network(s) associated with the overlay or NSX Transport network…

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RFC 6598 – IANA Reserved Address Space

Just a quick post to make reference to RFC 6598 and the IANA reserved address space which spans –


As detailed in the RFC description, it is intended for use on Service Provider networks however, it may be used in a manner similar to RFC 1918 private address space on routing equipment that is able to do address translation across router interfaces when the addresses are identical on two different interfaces.

From an NSX perspective, optimal use case is between a NSX Distributed Logical Router (NSX Tier-1 Router) and Edge Router (NSX Tier-0 Router). All good!

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