RDP to VMs in Overlay segments shows blank screen and reconnecting pop-ups
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RDP to VMs in Overlay segments shows blank screen and reconnecting pop-ups

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Article ID: 414100

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Updated On:

Products

VMware NSX

Issue/Introduction

  • Blank screen is displayed when trying to RDP to VMs in overlay segments.

  • This is followed by reconnecting messages as below


  • Packet captures were collected on the source and destination machines , TCP retransmissions and messages highlighting that previous packets are missing were observed.


  • The MSS advertised by both parties is 1460 (default, though it may vary), and frames with an MSS equal to or greater than 1460 are being retransmitted.

  • Ping to the destination machine with higher MTU fails
    ping <destination> -f -l <packet_size>  

 

Environment

VMware NSX

Cause

The packet size, including the overhead from the NSX overlay headers (e.g., 1460 + 20 + 20 + 58 approx. bytes), will exceed the MTU if it is configured to a value less than 1558.

Resolution

Since the geneve header has the do not fragment(DF) bit set , the packets that exceeds the configured MTU will be dropped and hence will be retransmitted.

Check the MTU configured in NSX and switches/routers in the physical network , set it to 1600bytes or more.

Additional Information

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