User's Manual

483
Chapter 65 IP Hardware Subnet Routing
Configuration
65.1 IP Hardware Subnet Configuration Task
65.1.1 Overview
IP hardware subnet routing is similar to IP fast exchange.
When the IP hardware subnet routing is not enabled, before forwarding message containing the IP address A
at the next hop, the switch first checks whether the item of destination A exists in the IP cache of hardware. If
the item exists, the message will be forwarded through hardware. If the item does not exist, the message is
sent to CPU and then processed through software. IP hardware subnet routing items include the destination
subnet, mask, IP address of the next hop, interface and so on. When the IP hardware subnet routing is enabled,
after the IP cache fails to be matched, the system is to check the IP hardware subnet routing items. If the
matched item is found, the message will be directly forwarded through the next-hop IP address and the
interface designated in the matched item. If the IP hardware subnet routing item is not found, the message will
be sent to CPU for processing.
The IP hardware subnet routing has two modes: automatic and manual. In manual mode, you need
to manually configure all routing items required by the IP hardware subnet routing. Note that
routing items having longer mask of destination subnet should be configured earlier. In automatic
mode, the system automatically addes the known routes to the hardware subnet routing. All the
procedure is automatic after the hardware subnet routing is started.
Model Mode Supported
3224 / 3224M / 6508 manual mode
Other layer-3 swicthes automatic mode
65.1.2 Configuring IP Hardware Subnet Routing
Perform the following steps to configure the IP hardware subnet routing：
Step Command Description
1 [
no
]
ip exf
{
default
| destination mask}
{
cpu
| nexthop vlan vlanid}
Add or delete a hardware subnet route.
Deleting a hardware subnet route requires to
specify the destination network and mask.
Replace
destination
and
mask
in the
command line with
default
when you delete
a route. In this case, The next hop is not CPU.
The command is effective only in manual
configuration mode.
2 [
no
]
ip exf
Enable or disable the IP hardware subnet
routing.
65.2 Configuration Example
Pay attention to the following content when you configure the routing items: