3Com CoreBuilder 2500 - Overlapped IP Vlans

About VLANs 2-7
Overlapped IP VLANs You can assign network layer information to IP VLANs so you can manage
your VLANs by subnetwork. The CoreBuilder 2500 system makes
flooding decisions by first matching the incoming frame using the
protocol (IP) and then matching the frame with Layer 3 subnetwork
information. If the received data is IP but does not match any defined IP
subnetwork VLAN, the data is flooded within all IP VLANs using the
relevant switch port.
For example, you can configure two overlapping IP VLANs for ports 1
through 10 as follows:
■ IP VLAN 1 — Subnetwork 158.101.112.0, ports 1 through 10, with
subnet mask 255.255.255.0
■ IP VLAN 2 — Subnetwork 158.101.113.0, ports 1 through 10, with
subnet mask 255.255.255.0
The following example shows how flooding decisions are made using
overlapping IP VLANs. The example assumes a 12-port switch.
VLAN Index VLAN Protocol
Network
Address/Mask
VLAN Ports
1 Default none 1 – 12
2 IP 158.103.122.0/
255.255.255.0
1 – 6
3 IP 158.103.123.0/
255.255.255.0
6 – 12
Data received on
this port
Is flooded on
this VLAN
Because
IP subnetwork
158.103.122.2
on port 6
VLAN 2 The IP network layer matches the Layer 3
address for VLAN 2.
IP subnetwork
158.103.123.2
on port 6
VLAN 3 The IP network layer matches the Layer 3
address for VLAN 3.
IP subnetwork
158.103.124.2
on port 6
VLAN 2 and
VLAN 3
The IP network layer does not match any
Layer 3 address for IP VLANs.
IPX on port 6 VLAN 1 The IPX frame does not match any defined
VLAN.