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Software Overview
December 2000
8 - 19
•
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.
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.
H1
H2
Router
209.157.1.1
209.157.2.1
Route once...
Switch many
Link
Activity
Link
Activity
Power
Console
FDX
100
Link / Act
FDX
100
Link / Act
FDX
100
Link / Act
FDX
100
Link / Act
FDX
100
Link / Act
FDX
100
Link / Act
Summary of Contents for Switch and Router
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Page 1070: ...Foundry Switch and Router Installation and Configuration Guide Index 18 December 2000 ...