Steps to reproduce:
configure interface and vrrp
set interfaces ethernet eth1 vif 92 address '192.168.112.14/31' set high-availability vrrp group v92 interface 'eth1.92' set high-availability vrrp group v92 no-preempt set high-availability vrrp group v92 priority '110' set high-availability vrrp group v92 virtual-address '172.18.92.1/24' set high-availability vrrp group v92 vrid '4'
my router owns both ip's on same interface eth1.92, because I am not using rfc3768-compatibility
olof@vyos:~$ show interfaces ethernet eth1 vif 92 eth1.92@eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 00:50:56:bc:ff:21 brd ff:ff:ff:ff:ff:ff inet 192.168.112.14/31 scope global eth1.92 valid_lft forever preferred_lft forever inet 172.18.92.1/24 scope global eth1.92 valid_lft forever preferred_lft forever
then configure dhcp-relay
set service dhcp-relay interface 'eth1.92'
When tcpdumping the dhcp-relay packets, I can see that the vyos router is sending with the "wrong" relay-agent-address, it is using 192.168.112.14.
Now, the problem, is that there is no subnet scope defined on the dhcp-server that uses 192.168.112.14/31.
If the dhcp-relay-agent-address would have been the vrrp-IP 172.18.92.1, the server would understand which dhcp-scope to use.