VXLAN: Loss of Connectivity Between Two VMs After Idle Time on KVM Hosts – CloudStack 4.20

[lexmora]

Description:

Hello,

I hope you're doing well, I've recently returned to using CloudStack after a few years, and I'm currently facing a VXLAN connectivity issue between two virtual machines deployed on different KVM hosts.

Issue Summary:

Two VM's are deployed on separate KVM Hosts.
VXLAN bridges and interfaces are correctly created by CLoudStack.
Initial connectivity work fine -- VM's can ping each other and the gateway (Virtual Router).
After stopping traffic between them and waiting appoximately 5 minutes, the VMs can no loger communicate with each other.
The issue affects both directions (bi'directional connectivity loss).
The bridge fdb show command no longer shows the remote MAC addresses associated with the VXLAN interface.
This leads to traffic being dropped, and ping fails to resume.
Temporary Workaround:
The only way to restore traffic is by manually bringing down and up the physical interface on the bond carrying the VXLAN traffic.

Environment Details:

3 KVM Hosts (Kernel 6.2.0)

CloudStack version 4.20.0.0

Advaced Zone

Traffic types configured:

Management: VLAN
Storage: VLAN
Guest: VXLAN
public VLAN
VXLAN is configured using multicast
Native Linux bridge is in use (not OVS)

IGMP Snooping is disable on the physical switches

Concers and Question:

Why does VXLAN stop learning or maintaining remote VM MAC addresses after idle time?
is this a know issue with VXLAN multicast setup?
Are there kernel or bridge parameters that should be adjusted (e.g., aging time)?

Thanks you in advance for your help and support

[boring-cyborg]

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