One or more devices are unreachable. Resolve any communication problems before attempting to sync.

@Hannes Rapp,

Thanks for the reply. Here's the information you requested.

[root@ust-f5ltm-01:Active:Disconnected] config  tmsh list net vlan HA
net vlan HA {
    if-index 320
    interfaces {
        1.3 { }
    }
    tag 74
}

[root@ust-f5ltm-02:Standby:Disconnected] config  tmsh list net vlan HA
net vlan HA {
    if-index 160
    interfaces {
        1.3 { }
    }
    tag 74
}

[root@ust-f5ltm-01:Active:Disconnected] config  tmsh list net self 192.168.74.1net self 192.168.74.1 {
    address 192.168.74.1/24
    allow-service {
        default
    }
    traffic-group traffic-group-local-only
    vlan HA
}

[root@ust-f5ltm-02:Standby:Disconnected] config  tmsh list net self 192.168.74.2
net self 192.168.74.2 {
    address 192.168.74.2/24
    allow-service {
        default
    }
    traffic-group traffic-group-local-only
    vlan HA
}

[root@ust-f5ltm-01:Active:Disconnected] config  tmsh list cm device ust-f5ltm-01.sdtest.local | grep -v modules
cm device ust-f5ltm-01.sdtest.local {
    base-mac 0:50:56:8e:44:6a
    build 39.0
    cert dtdi.crt
    chassis-id 420e0720-8e3c-6e11-72fb91cf1a1f
    configsync-ip 192.168.74.1
    edition "VE Trial 11.3.0-HF1 (based on BIGIP 11.3.0HF6)"
    failover-state active
    hostname ust-f5ltm-01.sdtest.local
    key dtdi.key
    management-ip 172.30.54.14
    marketing-name "BIG-IP Virtual Edition"
    mirror-ip 192.168.74.1
    multicast-ip any
    platform-id Z99
    product BIG-IP
    self-device true
    time-zone EDT
    unicast-address {
        {
            effective-ip 192.168.74.1
            effective-port cap
            ip 192.168.74.1
        }
        {
            effective-ip 172.30.54.14
            effective-port cap
            ip 172.30.54.14
        }
    }
    version 11.3.0
}

[root@ust-f5ltm-02:Standby:Disconnected] config  tmsh list cm device ust-f5ltm-02.sdtest.local | grep -v modules
cm device ust-f5ltm-02.sdtest.local {
    base-mac 0:50:56:8e:2f:3e
    build 39.0
    cert dtdi.crt
    chassis-id 420e4348-0c60-6c83-510c01f5f0f3
    configsync-ip 192.168.74.2
    edition "VE Trial 11.3.0-HF1 (based on BIGIP 11.3.0HF6)"
    failover-state standby
    hostname ust-f5ltm-02.sdtest.local
    key dtdi.key
    management-ip 172.30.54.24
    marketing-name "BIG-IP Virtual Edition"
    mirror-ip 192.168.74.2
    multicast-ip any
    platform-id Z99
    product BIG-IP
    self-device true
    time-zone EDT
    unicast-address {
        {
            effective-ip 192.168.74.2
            effective-port cap
            ip 192.168.74.2
        }
        {
            effective-ip 172.30.54.24
            effective-port cap
            ip 172.30.54.24
        }
    }
    version 11.3.0
}
`

This is all I see in /var/log/ltm during the time frame that I initiated the config sync:

`Apr  9 11:00:01 ust-f5ltm-01 notice mcpd[4828]: 01071431:5: Attempting to connect to CMI peer 192.168.74.2 port 6699
Apr  9 11:00:01 ust-f5ltm-01 notice mcpd[4828]: 01071432:5: CMI peer connection established to 192.168.74.2 port 6699
Apr  9 11:00:01 ust-f5ltm-01 notice mcpd[4828]: 0107143c:5: Connection to CMI peer 192.168.74.2 has been removed
...
Apr  9 11:17:26 ust-f5ltm-01 notice mcpd[4828]: 01071431:5: Attempting to connect to CMI peer 192.168.74.2 port 6699
Apr  9 11:17:26 ust-f5ltm-01 notice mcpd[4828]: 01071432:5: CMI peer connection established to 192.168.74.2 port 6699
Apr  9 11:17:26 ust-f5ltm-01 notice mcpd[4828]: 0107143c:5: Connection to CMI peer 192.168.74.2 has been removed
[root@ust-f5ltm-01:Active:Disconnected] config 

As far as the SOLs, I have tried a few of them. I am actually nearing the end of SOL13946 now. So far, the only thing I found was that I didn't have NTP configured. I went ahead and configured NTP on both LTM's, rebooted, and even rebuilt the trusts to no avail.

Let me know if I can grab anything else that might help,

SDTechOps