Networking and Virtual Switch Configuration
The virtual switch
AHV networking is built on Open vSwitch. Every host has a default bridge, br0, which carries the host management IP, the controller VM's IP, and VM traffic unless you separate them. A cluster also has a virtual IP (VIP) used to reach Prism Element, plus an optional iSCSI data services IP for external hosts using the Volumes block service.
Uplinks and bonds
Physical NICs are bonded into an uplink set. The bond mode decides behaviour: active-backup keeps one link live, balance-slb spreads flows by hash with no switch configuration required, and LACP (802.3ad) aggregates links but needs a matching port-channel on the switch. LACP configured on the host without switch-side setup is the classic outage.
VLANs
VLANs are created on the virtual switch as tagged networks; a VM attaches to a VLAN by selecting that network. The CVM does not need an address on every VLAN, and untagged traffic rides the native VLAN.
Traps
Questions often present 'just enable LACP on the host' as a safe fix - it is not, unless the switch is prepared. Another trap is treating the cluster VIP as a per-host address: it floats and serves management/API access only. Changing a bond or adding a VLAN on a live cluster can briefly interrupt traffic, so plan a window.
Rule of thumb
If you do not control the switch, choose balance-slb; it gives link redundancy with zero switch-side configuration.