Layer 3 Routing Features - Foundry Networks Switch and Router Installation And Configuration Manual

Foundry Switch and Router Installation and Configuration Guide
After the Layer 2 Switch makes an entry in its CAM for the IP destination, it directly decrements the TTL in and
forwards all subsequent IP packets for that destination address, bypassing the router and thereby reducing router
overhead. The dotted arrow to the router represents the packets that are virtually routed, but actually switched by
the Foundry Layer 2 Switch.
NOTE: Foundry routers typically route at wire speed, so IP switching generally is most useful for off-loading
slower third-party routers.
IPX Router Acceleration
IPX router acceleration (IPX switching), like IP router acceleration, enables a Foundry Layer 2 Switch to off-load a
router. In the case of IPX router acceleration, the Foundry switch performs ASIC-based Ethernet 802.2 and 802.3
forwarding at wire speed to off-load an IPX router.
NOTE: Router acceleration is supported only on the FastIron Backbone and TurboIron Backbone Layer 2
Switches.
IP and IPX Router Acceleration Policies
When IP or IPX router acceleration is enabled on a Foundry Layer 2 Switch, it makes entries in its CAM and
directly forwards IP or IPX traffic by default. If you want to control the addresses for which the Layer 2 Switch
provides Layer 3 router acceleration, you can define route service filters.
The CLI commands and Web management or IronView interface selections for Layer 3 filters are the same as
those for standard IP or IPX filters. However, the action that occurs when a deny filter becomes true is different:
• When you are using standard IP or IPX routing, accept filters forward packets and deny filters drop packets.
• When you are using IP or IPX router acceleration instead, accept filters switch packets and bypass the router.
Deny filters pass traffic to the router instead of switching the traffic directly. In IP and IPX router acceleration,
deny filters do not drop packets.
See "Router Acceleration Policies" on page C-18 for more information.

Layer 3 Routing Features

The following sections describe the Layer 3 routing features listed in Table 8.1 on page 8-2. Foundry routers
provide traditional Layer 3 routing at wire speeds with support for the following routing protocols:
• Internet Protocol (IP)
• IP Routing Information Protocol (RIP)
• Open Shortest Path First (OSPF)
• Internet Packet Exchange (IPX)
• IPX RIP
• IPX Service Advertisement Protocol (SAP)
• AppleTalk
The following sections describe the Foundry router support for the protocols listed above and the additional
routing features.
Multi-Netting
Multi-netting allows you to assign multiple IP or IPX protocol interfaces to the same physical port on the switch or
router. Foundry routers support multi-netting for IP and IPX.
8 - 20 December 2000