ip route del 1.2.3.4/24 via 1.2.3.4
ip route add 1.2.3.4/24 via 1.2.3.4 metric 1234
root@proxmox:~# ip route show
default via 172.16.1.1 dev vmbr0 proto kernel onlink
172.16.1.0/24 dev vmbr0 proto kernel scope link src 172.16.1.13
172.16.1.0/24 dev vmbr2 proto kernel scope link src 172.16.1.101
172.16.1.0/24 dev vmbr1 proto kernel scope link src 172.16.1.100