pfSense

Set up a CARP VIP between two nodes.
Primary:

vtnet4: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
    description: WAN2
    options=800b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LINKSTATE>
    ether 0e:a5:98:66:d0:cf
    inet6 fe80::ca5:98ff:fe66:d0cf%vtnet4 prefixlen 64 scopeid 0x5
    inet 172.25.227.18 netmask 0xffffff00 broadcast 172.25.227.255
    inet 172.25.227.17 netmask 0xffffff00 broadcast 172.25.227.255 vhid 242
    carp: MASTER vhid 242 advbase 1 advskew 0
    media: Ethernet 10Gbase-T <full-duplex>
    status: active
    nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

Secondary:

vtnet4: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
    description: WAN2
    options=800b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LINKSTATE>
    ether e2:66:f3:ea:8a:ba
    inet6 fe80::e066:f3ff:feea:8aba%vtnet4 prefixlen 64 scopeid 0x5
    inet 172.25.227.19 netmask 0xffffff00 broadcast 172.25.227.255
    inet 172.25.227.17 netmask 0xffffff00 broadcast 172.25.227.255 vhid 242
    carp: INIT vhid 241 advbase 1 advskew 100
    carp: BACKUP vhid 242 advbase 1 advskew 100
    media: Ethernet 10Gbase-T <full-duplex>
    status: active
    nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

Hmm. The old VIP was also not cleared from the interface - CARP INIT state. That is from the prior test in which I changed the VHID from 241 to 242.

Status > CARP shows MASTER/BACKUP

Change the VHID on the primary from 242 to 243. Save. Apply

Status > CARP Shows MASTER/ BLANK

Primary:

vtnet4: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
    description: WAN2
    options=800b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LINKSTATE>
    ether 0e:a5:98:66:d0:cf
    inet6 fe80::ca5:98ff:fe66:d0cf%vtnet4 prefixlen 64 scopeid 0x5
    inet 172.25.227.18 netmask 0xffffff00 broadcast 172.25.227.255
    inet 172.25.227.17 netmask 0xffffff00 broadcast 172.25.227.255 vhid 243
    carp: MASTER vhid 243 advbase 1 advskew 0
    media: Ethernet 10Gbase-T <full-duplex>
    status: active
    nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

Secondary:

vtnet4: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
    description: WAN2
    options=800b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LINKSTATE>
    ether e2:66:f3:ea:8a:ba
    inet6 fe80::e066:f3ff:feea:8aba%vtnet4 prefixlen 64 scopeid 0x5
    inet 172.25.227.19 netmask 0xffffff00 broadcast 172.25.227.255
    carp: INIT vhid 241 advbase 1 advskew 100
    carp: INIT vhid 242 advbase 1 advskew 100
    media: Ethernet 10Gbase-T <full-duplex>
    status: active
    nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

Edit / Save / Apply the VIP on the secondary:

vtnet4: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
    description: WAN2
    options=800b8<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,LINKSTATE>
    ether e2:66:f3:ea:8a:ba
    inet6 fe80::e066:f3ff:feea:8aba%vtnet4 prefixlen 64 scopeid 0x5
    inet 172.25.227.19 netmask 0xffffff00 broadcast 172.25.227.255
    inet 172.25.227.17 netmask 0xffffff00 broadcast 172.25.227.255 vhid 243
    carp: INIT vhid 241 advbase 1 advskew 100
    carp: INIT vhid 242 advbase 1 advskew 100
    carp: BACKUP vhid 243 advbase 1 advskew 100
    media: Ethernet 10Gbase-T <full-duplex>
    status: active
    nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

(I don't have a preview option in redmine any more. Sorry for any misformatting.)