Intel 480T, User Manual

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C H A P T E R 1 0 IP Unicast Routing
Additional verification commands include the following:
•
show iparp
— Displays the IP ARP table of the system.
•
show ipfdb
— Displays the hosts that have been transmitting or
receiving packets, and the port and VLAN for each host.
•
show ipconfig
— Displays configuration information for one
or more VLANs.
VLAN Aggregation
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 super-VLAN is defined with the
desired IP address, but without any member ports (unless it is
running ESRP). The sub-VLANs use the IP address of the super-
VLAN as the default router address. Groups of clients are then
assigned to sub-VLANs that have no IP address, but are members
of the super-VLAN. In addition, clients can be informally allocated
any valid IP addresses within the subnet. Optionally, you can
prevent communication between sub-VLANs for isolation
purposes. As a result, sub-VLANs 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 super-
VLAN. These IP addresses are
only used to respond to ICMP ping
packets to verify connectivity.
Figure 19 illustrates VLAN aggregation.