Networking
What this domain tests
Basic AHV networking: virtual switches, bridges, bonds, VLANs, uplinks, and IP addressing.
Core rules and concepts
- AHV uses Open vSwitch. vs0 is the default virtual switch, and bridges connect VM NICs to VLANs.
- A bond aggregates physical NICs. Active-backup needs no switch configuration. LACP requires a matching LAG on the switch. balance-slb uses hash-based load balancing and may need switch configuration.
- VLANs are trunked to hosts. A VM NIC is placed on a VLAN-backed bridge. The native/default VLAN is untagged.
- Jumbo frames must be consistent end to end; a mismatch causes fragmentation or drops.
- IPAM can allocate addresses. DNS and NTP must be correct for cluster health.
- Multiple VLANs can share a bond, but check uplink capacity and failover behavior.
Worked example
A web VM needs VLAN 120. Create or verify a bridge for VLAN 120 on the host, attach the VM NIC to it, and ensure the switch port is a trunk allowing VLAN 120. If the port is an access port on VLAN 120, the guest should be untagged instead. For LACP, configure the switch LAG first; otherwise the bond will not pass traffic.
Traps
Do not mix LACP and active-backup on the same bond. Do not assume VM VLAN connectivity because the host management IP works. Do not tag the same VLAN on both the guest and the AHV network unless that is intentional. Do not enable jumbo frames on one side only.