The completion help show the subnet id could start from 0, but it is not accepted
vyos@r14# set service dhcp-server shared-network-name LANv4 subnet 100.64.0.0/24 subnet-id
Possible completions:
<0-4294967295> Unique subnet ID
[edit vrf name red]
vyos@r14# set service dhcp-server shared-network-name LANv4 subnet 100.64.0.0/24 subnet-id 0
Number is not in any of allowed ranges
Invalid value
Value validation failed
Set failed
[edit vrf name red]
vyos@r14# set service dhcp-server shared-network-name LANv4 subnet 100.64.0.0/24 subnet-id 1
[edit vrf name red]
vyos@r14#