Comment 2 for bug 1804861

Seems to work here. With the config below; 'ip link' does show the bond device and the physical interfaces having a MTU of 9000, and the two VLANs having a MTU of 1500, as per the configuration.

What could be the difference that breaks this deployment?

network:
    version: 2
    ethernets:
        ens6:
            set-name: ens6
            match:
                macaddress: 52:54:00:25:ba:4f
            mtu: 9000
        ens7:
            set-name: ens7
            match:
                macaddress: 52:54:00:02:86:3b
            mtu: 9000
    bonds:
        bond0:
            interfaces:
            - ens6
            - ens7
            macaddress: 00:de:ad:be:ef:01
            mtu: 9000
            parameters:
                down-delay: 0
                lacp-rate: fast
                mii-monitor-interval: 100
                mode: 802.3ad
                up-delay: 0
                transmit-hash-policy: layer3+4
    vlans:
        bond0.804:
            mtu: 1500
            id: 804
            link: bond0
            addresses:
                - 10.20.16.50/24
        bond0.1:
            mtu: 1500
            id: 1
            link: bond0
            addresses:
            - 10.3.67.31/20
            gateway4: 10.3.67.1
            nameservers:
                addresses:
                - 10.3.67.22
                search:
                - cloud