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MTU Drops from 1400 to 1200 Causing AVS VM Connectivity Loss

  • 1.  MTU Drops from 1400 to 1200 Causing AVS VM Connectivity Loss

    Posted Dec 08, 2025 08:35 PM

    Hello,

    I am having trouble with MTU to/from VMs in AVS, it keeps dropping down to 1200, this doesn't effect VMs in Azure native - only VMs in AVS. Any ideas?

    When I set the MTU to 1400 on my on-premises VPN and in the HCX network profile, the connection works correctly for a few minutes, but then the MTU drops to 1200. This reduction causes my VMs in Azure VMware Solution (AVS) to lose connectivity.

    Architecture:

    On-prem-Site-to-Site VPN → Hub VNet → Azure Firewall → AVS



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