Brocade TurboIron 24X Series Configuration Guide - Manual (Page 408)

374 Brocade TurboIron 24X Series Configuration Guide
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Routing between VLANs
Broadcast leaks
A dynamic port becomes a member of a Layer 3 protocol VLAN when traffic from the VLAN's
protocol is received on the port. After this point, the port remains an active member of the protocol
VLAN, unless the port does not receive traffic from the VLAN's protocol for 20 minutes. If the port
does not receive traffic for the VLAN's protocol for 20 minutes, the port ages out and is no longer
an active member of the VLAN.
To enable a host that has been silent for awhile to send and receive packets, the dynamic ports
that are currently members of the Layer 3 protocol VLAN "leak" Layer 3 broadcast packets to the
ports that have aged out. When a host connected to one of the aged out ports responds to a leaked
broadcast, the port is added to the protocol VLAN again.
To "leak" Layer 3 broadcast traffic, an active port sends 1/8th of the Layer 3 broadcast traffic to the
inactive (aged out) ports.
Static ports do not age out and do not leak broadcast packets.
Super aggregated VLANs
You can aggregate multiple VLANs within another VLAN. This feature allows you to construct Layer 2
paths and channels. This feature is particularly useful for Virtual Private Network (VPN)
applications in which you need to provide a private, dedicated Ethernet connection for an individual
client to transparently reach its subnet across multiple networks.
For an application example and configuration information, refer to “Configuring super aggregated
VLANs” on page 399.
Trunk group ports and VLAN membership
A trunk group is a set of physical ports that are configured to act as a single physical interface.
Each trunk group port configuration is based on the configuration of the lead port, which is the
lowest numbered port in the group.
If you add a trunk group lead port to a VLAN, all of the ports in the trunk group become members of
that VLAN.
Routing between VLANs
Layer 3 Switches can locally route IP, IPX, and Appletalk between VLANs defined within a single
router. All other routable protocols or protocol VLANs (for example, DecNet) must be routed by
another external router capable of routing the protocol.
Virtual routing interfaces (Layer 3 Switches only)
You need to configure virtual routing interfaces if an IP, IPX, or Appletalk protocol VLAN, IP subnet
VLAN, AppleTalk cable VLAN, or IPX network VLAN needs to route protocols to another port-based
VLAN on the same router. A virtual routing interface can be associated with the ports in only a
single port-based VLAN. Virtual router interfaces must be defined at the highest level of the VLAN
hierarchy.