Networking
AHV host networking
Each AHV host runs Open vSwitch (OVS). The default topology is a bridge (br0), a bond (bond0) aggregating the physical uplinks, and per-VLAN virtual networks that VMs attach to. The CVM also sits on this fabric, so management traffic and guest traffic must be planned.
Bond modes are a favourite exam topic:
- active-backup - the default; no switch-side configuration required; one link active at a time.
- LACP (802.3ad) - requires a matching LAG on the physical switch; aggregates throughput.
- balance-slb / balance-tcp - switch-independent or LACP-assisted load balancing variants.
Other concepts: VLAN segmentation on virtual networks, IPAM for automated address assignment, jumbo frames (MTU must match end-to-end), and Flow Network Security - Nutanix microsegmentation that applies policy to VM NICs using categories, in monitor or enforce mode.
Traps
- Choosing LACP when the switch team cannot configure a port-channel - the bond will not come up correctly. If switch-independent redundancy is the requirement, the answer is active-backup.
- Assuming Flow policies take effect immediately - in monitor mode they only log traffic.
- Forgetting that VLAN 0/untagged is a real choice and that a VM must be on a network with a VLAN that exists on the host.
- Changing bond mode or MTU on a live host can be disruptive; plan maintenance.
Rule of thumb
Two uplinks, no switch cooperation available → active-backup. Switch team can build a LAG → LACP for aggregate bandwidth. Security requirement phrased as "isolate VMs from each other without VLAN sprawl" → Flow with categories.