AHV use Open VSwitch(OVS) to connect the CVM, Hypervisor and gest Virtual machines to each other and to physical network.

Open VSwitch:

Open VSwitch is an opensource software switch implementation in the Linux Kernel. OVS acts like a Layer-2 switch which means its maintain the MAC Address table. Host, VMs connect to Virtual Ports on the switch.OVS support common switch features like VLAN Tagging, Load Balancing and link Aggregation Control Protocol (LACP). Each AHV Host server maintain and OVS instance and all OVS instance combine to form a single logical switch.

Bridges:

Bridges act as virtual switch to manage traffic between physical and virtual network interfaces. By default AHV configuration includes an OVS called Br0 / Br0-up and a native Linux Bridge call Virbr0. The virbr0 Linux bridge is responsible for management and storage communication between CVM and AHV host. All the other traffic (storage, host, VM) flows through br0 OVS bridge.

Ports:

Ports are logical entity created in bridge that represent connectivity to virtual switch.

Bonds:

Bonded ports aggregate the physical interfaces on the AHV host. By default, the system creates a bond named br0-up /Br0 having all physical interfaces.

OVS bonds supports multiple load-balancing modes, including active-backup, balance-slb, and balance-tcp.

I faced the strange issues with one of my customer, where Exchange Database was not getting list in GUI, as well as when I try to list the Databases using Exchange Management Shell I got the error saying unable to find “Mailbox XXXXX “ DB.

After seen this error, I opened ADSI Edit and found someone didn’t decommission the old Exchange properly. Old Exchange Sever was removed and Old Databases still exists in Active Directory Schema. After identify this , I just clean-up the old Database entries and do a refresh on ECP all databases got list immediately.

• Login to domain controller with administrative account.
• Navigate to Start –> Run –> ADSIEdit.msc and hit enter
• Click on Action –> Connect to –> Select Configuration under “Select a well known naming Context:”

Navigate to CN=Configuration, DC=DOMAINNAME, DC=COM

Replace DC=DOMAINNAME, DC=COM with your domain name

Expand the CN=Services –> CN=Microsoft Exchange

After Removing the all old DBs, my current DBs started getting listed in Exchange GUI & Management Shell.

Note: I would recommend always use proper methods to old exchange servers, use adsi edit only incase Exchange server is no more in the environment or its got crashed. Improper use of ADSI edit may harm the active directory schema, so be very careful while modifying/deleting any values /keys.