Vlan Overview; Types Of Vlans - Foundry Networks FESX Manual

Foundry Configuration Guide for the FESX, FSX, and FWSX

VLAN Overview

The following sections provide details about the VLAN types and features supported on the FastIron family of
switches.

Types of VLANs

You can configure the following types of VLANs on Foundry devices.
• Layer 2 port-based VLAN – a set of physical ports that share a common, exclusive Layer 2 broadcast domain
• Layer 3 protocol VLANs – a subset of ports within a port-based VLAN that share a common, exclusive
broadcast domain for Layer 3 broadcasts of the specified protocol type
• IP sub-net VLANs – a subset of ports in a port-based VLAN that share a common, exclusive sub-net
broadcast domain for a specified IP sub-net
• IPv6 VLANs – a subset of ports in a port-based VLAN that share a common, exclusive network broadcast
domain for IPv6 packets
• IPX network VLANs – a subset of ports in a port-based VLAN that share a common, exclusive network
broadcast domain for a specified IPX network
• AppleTalk cable VLANs – a subset of ports in a port-based VLAN that share a common, exclusive network
broadcast domain for a specified AppleTalk cable range
When a Foundry device receives a packet on a port that is a member of a VLAN, the device forwards the packet
based on the following VLAN hierarchy:
• If the port belongs to an IP sub-net VLAN, IPX network VLAN, or AppleTalk cable VLAN and the packet
belongs to the corresponding IP sub-net, IPX network, or AppleTalk cable range, the device forwards the
packet to all the ports within that VLAN.
• If the packet is a Layer 3 packet but cannot be forwarded as described above, but the port is a member of a
Layer 3 protocol VLAN for the packet's protocol, the device forwards the packet on all the Layer 3 protocol
VLAN's ports.
• If the packet cannot be forwarded based on either of the VLAN membership types listed above, but the packet
can be forwarded at Layer 2, the device forwards the packet on all the ports within the receiving port's port-
based VLAN.
Protocol VLANs differ from IP sub-net, IPX network, and AppleTalk VLANs in an important way. Protocol VLANs
accept any broadcast of the specified protocol type. An IP sub-net, IPx network, or AppleTalk VLAN accepts only
broadcasts for the specified IP sub-net, IPX network, or AppleTalk cable range.
NOTE: Protocol VLANs are different from IP sub-net, IPX network, and AppleTalk cable VLANs. A port-based
VLAN cannot contain both an IP sub-net, IPX network, or AppleTalk cable VLAN and a protocol VLAN for the
same protocol. For example, a port-based VLAN cannot contain both an IP protocol VLAN and an IP sub-net
VLAN.
Layer 2 Port-Based VLANs
On all Foundry devices, you can configure port-based VLANs. A port-based VLAN is a subset of ports on a
Foundry device that constitutes a Layer 2 broadcast domain.
By default, all the ports on a Foundry device are members of the default VLAN. Thus, all the ports on the device
constitute a single Layer 2 broadcast domain. You can configure multiple port-based VLANs. When you configure
a port-based VLAN, the device automatically removes the ports you add to the VLAN from the default VLAN.
You can configure up to 4094 port-based VLANs on a Layer 2 Switch or Layer 3 Switch. On both device types,
valid VLAN IDs are 1 – 4095. You can configure up to the maximum number of VLANs within that ID range.
11 - 2 © Foundry Networks, Inc. December 2005