A virtualized server might contain multiple virtual NICs over the same physical link. You can assign these VNICs to VMs. Traditionally, a switch does not transmit packets back on the same link on which it receive the packets. Packets between VMs are looped back by the virtual switch within the host itself. Therefore, any policies that are configured on the external switch are not applied to inter-VM packets. With the support for EVB, Oracle Solaris and the switch enable inter-VM packets to be switched by the external switch after enforcing any policies on the inter-VM packets. For more information about VNICs, see Creating and Managing Virtual Networks.
In addition, Oracle Solaris with the support of EVB can exchange information about VNICs with the switch. This exchange of information enables the switch to automatically configure the VNIC properties such as bandwidth limits, bandwidth shares, and MTU on the network. In the absence of this feature, the server administrator and the network administrator must coordinate with each other to make changes on the switch every time a VNIC is created, modified, or deleted on the server. Extending the VNIC properties into the network leads to an efficient use of networking resources based on VNIC properties. For example, enforcing a bandwidth limit on packets after they arrive at the host is not very helpful because the packets might have already used up the link bandwidth.
Reflective relay is a feature that enables VMs that are using the VNICs over the same physical NIC to communicate through the external switch. The switch must support this capability. In Oracle Solaris, LLDP is extended to include an EVB type-length value (TLV) unit, which is used to determine if the switch supports reflective relay capability and to enable or disable reflective relay capability on the switch. Therefore, you can automate the detection and configuration of this capability on the switch by using LLDP only if the switch supports LLDP and EVB TLV unit. Otherwise, reflective relay feature must be manually configured on the switch. For information about how to manually configure reflective relay, refer to the switch manufacturer's documentation.
For more information about the reflective relay support in Oracle Solaris, see Controlling Switching Between VMs Over the Same Physical Port. For more information about the LLDP TLV units, see Information the LLDP Agent Advertises in Managing Network Datalinks in Oracle Solaris 11.3.
Oracle Solaris uses the Virtual Station Interface Discovery and Configuration Protocol (VDP) defined in IEEE 802.1Qbg to exchange VNIC information with the switch. If the switch supports VDP, then VNIC properties are automatically configured on the switch. This is similar to the host and switch exchanging physical link properties by using DCBX. When a VNIC is created, modified, or deleted, a VDP exchange is initiated between the host and the switch. This exchange enables the switch to allocate resources for the packets destined to the VNIC based on properties of the VNIC.
For more information about exchange of VNIC information between a system and an external switch in Oracle Solaris, see Exchanging VNIC Information by Using VDP and How VDP Exchanges VNIC Information.