VMs can't reach the gateway

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pludikovsky

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Nov 8, 2022
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Setup:
  • Network: 10.x.y.0/22
  • Gateway & DNS: 10.x.y.1
  • Proxmox: 10.x.y.241/22
    • vmbr0 contains bond0, which bonds 4 physical interfaces
  • VM: 10.x.(y+1).1/22
  • Firewall is off both on Proxmox and the VM

Situation:
  • I can ping the gateway from Proxmox and vice versa
  • I can ping Proxmox from the VM and vice versa
  • I can ping the VM from the gateway
  • I can't ping the gateway from the VM

Anyone got an idea what I missed? During the setup the VMs had a random IP via DHCP and everything worked as intended, after the setup this was changed to a fixed IP, still assigned via DHCP.
 
I think it would make things easier if you showed the values of 'x' and 'y', as the problem could be that you're assigning addresses which are not valid for the /22 netmask (normally it's 10.x.y.z/8 anyway).

Are the VMs running Linux? what does "ip route" show?

If the gateway is not in the assigned subnet (which depends on your values of 'x' and 'y') you may have to tell the VM that the gateway is on the link ("GatewayOnLink" if using systemd-networkd).
 
@reinob Network is 10.9.8.0/22, so 10.9.8.1-10.9.11.254. Gateway is 10.9.8.1, Proxmox is 10.9.8.241, VM is 10.9.9.1. And like I said, the gateway can ping the VM, it just doesn't work the other way around, but the gateway is pingable from other (non-VM) nodes.

@MarkusKo Just because the 10./8 network can be that size nothing requires it to be that size. It just means that range is reserved for private use.
 
the only thing i could think of is a subnet mask mismatch ...
double check the subnet mask on your vm and the dhcp server config

as you already stated in your 10.9.8.0/22 network it should be 255.255.252.0
 
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