VM deployed in NSX-T fails to communicate on segment for approx. 10 minutes
search cancel

VM deployed in NSX-T fails to communicate on segment for approx. 10 minutes


Article ID: 322498


Updated On:


VMware NSX Networking


  • After a VM has been deleted and redeployed using the same IP address, connectivity fails on the redeployed VM.
  • The redeployed VM may be a newly deployed VM or existing VM.
  • The connectivity fails for VM's on different subnet/segments.
  • The redeployed VM can ping and respond to pings from IP addresses on the same segment, on the same or different hosts.
  • The redeployed VM fails to respond to pings from IP address's in a different segment/subnet.
  • The redeployed VM has a new mac address, but uses the same IP address as the deleted VM.
  • Using packet capture tools, no traffic is observed leaving the new VM when not in same subnet/segment.
  • Listing the mac addresses known to the VDR (Virtual Distributed Router), still shows the deleted VM's mac address:
net-vdr -Nl <vdr-instance-ID>

DR 1e85f6db-f088-4f07-89e7-b7865220ede2 ARP Information :
Legend: [S: Static], [V: Valid], [P: Proxy], [I: Interface]
Legend: [N: Nascent], [L: Local], [D: Deleted], [K: linKlif]
Legend: [A: AutoRefresh]

Network Mac Flags Expiry Uptime SrcPort Refcnt Lif UUID
------- --- ----- ------ ------ ------- ------ ---------
<snip> 00:50:56:9d:c1:3d V 441 159 0 6 e5063480-f5ef-4d02-837e-1201beb185e8
Note: To find the VDR instance name used in the command above, use: net-vdr -Il


VMware NSX-T Data Center


The VM's operating system has failed to send out a GARP (Gratuitous ARP) packet when reusing the same IP.
The GARP will refresh all stale IP/MAC entries in NSX and is required by the VDR to update it IP address to MAC address mappings.


It is the VM operating systems responsibility to send out a GARP when the IP address is added.
This issue will not occur if the same IP address has not been used recently with a different MAC address.
It is always a good practice to send out GARP when IP address is added.

From the impacted VM, that is the redeployed VM, you can manually run an 'arping' command to update all devices of the new IP/MAC mapping:
arping -U -I eth0 -c 3
The IP address in the command should be the IP address of the redeployed VM and will result in a GARP being sent out with source and destination IP being the same and that of the newly deployed VM.