Differences between SVL and IVL in VLAN

The differences between SVL and IVL in VLANs support L2 Switches of VLANs. The L2 forwarding and MAC address maintenance methods have changed, the following describes two vswitches with different MAC address maintenance methods. The SVL L2 Switch SVL (Shared VLAN Learning) does not attach vlan id when Learning MAC addresses and creating MAC address tables, or its MAC address table is used for all VLAN sharing. The basic process of L2 Forwarding is as follows: (1) Add or refresh the MAC address table items based on the source MAC information of the received Ethernet frame; (2) search for the MAC address table based on the target MAC information. If no matching item is found, broadcast in the VLAN corresponding to the packet. (3) If a match is found, however, if the port corresponding to the table item does not belong to the VLAN corresponding to the packet, the frame is discarded. (4) If a match item is found and the port corresponding to the table item belongs to the VLAN corresponding to the packet, the packet is forwarded to this port. However, if the corresponding port of the table item is the same as the port on which the Ethernet frame is received, the frame is discarded. This type of L2 Switch Forwarding is basically the same as that of a common L2 Switch, but only the VLAN check is added during the forwarding process. Such a switch may encounter the following problems: the host (or network device) located in different VLANs has the same MAC address, because all VLANs of the svl switch share a MAC table, in this way, the ports in the corresponding MAC table will change constantly, and the packet forwarding of the two VLANs will also be affected, as shown in Case 1. In Figure 1, the packet sent by pc a of VLAN 10 to pc B is discarded because the MAC address table search result is inconsistent with the VLAN. Similarly, when mac B learns to PORT 2, communication between pc d and pc c of VLAN 20 may fail. In this way, although different hosts are isolated in different conflicting domains and broadcast domains, MAC addresses may affect communication between different VLANs. In practical applications, L2 switches in the SVL mode are rare. An IVL L2 Switch, IVL (Independent VLAN Learning), attaches a vlan id when Learning a MAC address and creating a MAC address table, the same MAC address can appear in different VLANs. In this way, each VLAN has its own independent MAC address table. The basic process of L2 Forwarding is as follows: (1) Add or refresh the MAC address table item based on the source MAC + VLAN-ID information of the received Ethernet frame; (2) search for MAC address table items based on the destination MAC + VLAN-ID. If no match is found, broadcast in the VLAN corresponding to the VLAN-ID; (3) if match table items can be found, forward to the corresponding port shown in the table, but if the port shown in the table is the same as the port on which the Ethernet frame is received, the frame is discarded. Forwarding problems that may occur on SVL switches can be solved in IVL switches. As shown in figure 2, the forwarding process of layer-2 vswitches in IVL mode is clearer and there is no mutual impact between VLANs, most L2 switches in actual application use this method.