Foundry Networks Switch and Router Installation And Configuration Manual page 1022

Foundry Switch and Router Installation and Configuration Guide
Router Acceleration Policies
You can configure Foundry Layer 2 and Layer 3 Switches to perform router acceleration by enabling Layer 3 IP or
IPX 3 switching. When you enable router acceleration, the device switches all IP or IPX route packets by default
after learning the outbound ports for the packets. By switching an IP or IPX packet, the Foundry Layer 2 or Layer
3 Switch provides increased network performance by bypassing slow routers.
NOTE: Router acceleration is supported only on the FastIron Backbone and TurboIron Backbone Layer 2
Switches.
NOTE: Foundry Layer 3 Switches route at wire speed. Router acceleration is useful for routers that do not route
at wire speed.
Switching the IP or IPX packets to bypass the router is the default router acceleration policy. You can modify the
policy by adding IP or IPX filters. The CLI commands and Web management panels for router acceleration filters
are the same as those used for IP and IPX forward filters. You configure the filters globally, then apply them to
specific ports. When you apply an IP or IPX filter to a port, you specify whether the filter applies to inbound
packets or outbound packets.
NOTE: A Foundry device can either route or switch IP or IPX, but cannot be configured to both route and switch
the same protocol.
IP and IPX forwarding filter behavior differs depending on whether the device is switching or routing:
• If the device is routing, the behavior is as described in "IP Access Policies" on page C-9.
• If the device is switching, the device accelerates packets that match a filter with a permit action. The device
does not drop packets that match a filter with a deny action; instead, the device sends these packets to the
router.
Figure C.2 shows an example of router acceleration policies. In this example, all outbound IP traffic on Port 2/1
except traffic destined for IP sub-net 128.24.26.0/24 is permitted to be directly switched at Layer 3, bypassing the
router. The traffic that is denied Layer 3 switching by policy 1 is sent to the router instead. The policies in this
example are applied to a port's outbound policy group. Therefore, all packets enter the Foundry device before
being filtered.
C - 18 December 2000