Netgear XCM8810 Chassis User Manual - Page 634

NETGEAR 8800 User Manual VLAN Aggregation Note: This feature is supported only on the platforms listed for this feature in the license tables in Appendix A, XCM8800 Software Licenses. VLAN aggregation is a feature aimed primarily at service providers. The purpose of VLAN aggregation is to increase the efficiency of IP address space usage. It does this by allowing clients within the same IP subnet to use different broadcast domains while still using the same default router. Using VLAN aggregation, a superVLAN is defined with the desired IP address. The subVLANs use the IP address of the superVLAN as the default router address. Groups of clients are then assigned to subVLANs that have no IP address, but are members of the superVLAN. In addition, clients can be informally allocated any valid IP addresses within the subnet. Optionally, you can prevent communication between subVLANs for isolation purposes. As a result, subVLANs can be quite small, but allow for growth without re-defining subnet boundaries. Without using VLAN aggregation, each VLAN has a default router address, and you need to use large subnet masks. The result of this is more unused IP address space. Multiple secondary IP addresses can be assigned to the superVLAN. Figure 66 illustrates VLAN aggregation. 1 2 3 4 A B 5 6 7 8 OSPF Rtr_Link VLAN_A OSPF Rtr_Link VLAN_B Super VLAN_1 IP address: a.b.c.1 mask: /24 Super VLAN_2 IP address: a.b.d.1 mask: /24 Super VLAN_3 IP address: a.b.e.1 mask: /24 Sub-VLAN n Sub-VLAN 3 Sub-VLAN 2 Sub-VLAN 1 Sub-VLAN n Sub-VLAN 3 Sub-VLAN 2 Sub-VLAN 1 Sub-VLAN n Sub-VLAN 3 Sub-VLAN 2 Sub-VLAN 1 EW_026 Figure 66. VLAN aggregation 634 | Chapter 20. IPv4 Unicast Routing