We attempted this approach using active-backup mode with ARP probes directed to one of the member IP addresses, but the interface on gw2 still remains down. Unfortunately, installing a switch is not an option for us. As an alternative, we will create a Link Aggregation interface with 2 member interfaces, where only one will be physically connected. We will keep you updated on the results.
gw2> cphaprob -a if
CCP mode: Manual (Unicast)
Required interfaces: 3
Required secured interfaces: 1
Interface Name: Status:
lo Non-Monitored
WAN UP
LAN1 Non-Monitored
LAN6 Non-Monitored
LAN8 (P) Inbound: DOWN (83331.8 secs)
Outbound: DOWN (506.6 secs)
SYNCBOND (S-HA) UP
S - sync, HA/LS - bond type, LM - link monitor, P - probing
Linux active-backup bond configuration
cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v6.1.0-23-amd64
Bonding Mode: fault-tolerance (active-backup)
Primary Slave: ens6f0 (primary_reselect always)
Currently Active Slave: ens6f0
MII Status: up
MII Polling Interval (ms): 0
Up Delay (ms): 0
Down Delay (ms): 0
Peer Notification Delay (ms): 0
ARP Polling Interval (ms): 1000
ARP Missed Max: 2
ARP IP target/s (n.n.n.n form): x.x.x.x //gw1 interface IP
NS IPv6 target/s (xx::xx form):
Slave Interface: ens6f0
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 1
Permanent HW addr: 6c:fe:54:8c:55:08
Slave queue ID: 0
Slave Interface: ens6f1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 6c:fe:54:8c:55:09
Slave queue ID: 0