VMware: vMotion migration socket connected returned: Already disconnected

Today a customer told me that he couldn’t vMotion virtual machines between a few hosts, he received this warning message:

Migration to host <<unknown>> failed with error Already disconnected

An unknown error has occurred.

vMotion migration socket connected returned: Already disconnected

Solution:

After some troubleshooting I’ve checked and tested:

– Same VMkernel (+ case sensitive) name;
– Same VLAN;
– Same subnet;
– Same default gateway;
– They configured unique ip-addresses;
– Host A can ping host B, vice versa;
– Ping is stable < 1 ms;
– But…

…reading KB1030267 I checked the MTU size, somebody configured the MTU size with a 9000 value at the Management / vMotion VMkernel..

The 9000 value was configured (at the hosts with the vMotion problem) but not at the physical switches, after revert to default value (1500) I was able to vMotion again, problem solved

Result:

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Sander

Sander Daems is founder and author of this blog and working as a Lead (Sr.) Consultant / Technical Project Lead at Unica ICT Solutions. Sander has 15+ years experience in IT, primary focus: virtualization, security and modern worksplace.

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