Foundry Networks Switch and Router Installation And Configuration Manual page 227

• NetBIOS
• Others
For more details on the value and configuration of VLANs, see "Configuring Virtual LANs (VLANs)" on page 25-1.
Routing Between VLANs
In addition to supporting the assignment of VLANs, Foundry routers support routing between VLANs using virtual
interfaces.
VLAN Tagging
VLAN tagging (802.1q) extends the boundaries of the VLAN by allowing creation of VLANs that cross switch
boundaries. This eases network management and ensures interoperability with other devices. See "VLAN
Tagging" on page 8-17.
IP Router Acceleration
IP router acceleration (IP switching) enables a Foundry Layer 2 Switch to perform ASIC-based forwarding and
aging of IP packets at wire speed. IP router acceleration is useful for off-loading IP routers, thus enhancing overall
throughput on the network. Figure 8.3 shows an example of a typical IP switching configuration.
NOTE: Router acceleration is supported only on the FastIron Backbone and TurboIron Backbone Layer 2
Switches.
Route once...
Link Link
Activity Activity
FDX
100
Console Link / Act
FDX
100
Power Link / Act
H1
209.157.1.1
Figure 8.3 Example IP router acceleration configuration
In this example, the Foundry Layer 2 Switch forwards the first IP packet it receives for IP address 209.157.2.1 to
the attached router. This is shown by the solid arrow pointing from the Foundry Layer 2 Switch to the router. The
router alters the packet for forwarding (updates the destination address and decrements the Time-to-Live) and
sends the packet back to the Foundry Layer 2 Switch for forwarding. The Foundry Layer 2 Switch forwards the
packet and also makes an entry in its CAM (Content Addressable Memory) containing the destination IP address
and the egress port, which is the port out of which the Layer 2 Switch sends the packet to reach its destination.
December 2000
FDX FDX
100 100
Link / Act Link / Act
FDX FDX
100 100
Link / Act Link / Act
Switch many
Router
Software Overview
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209.157.2.1
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