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11-12 Riverstone Networks RS Switch Router User Guide Release 8.0
Forwarding Mode IP Routing Configuration Guide
11.15 FORWARDING MODE
When the RS receives a packet for routing, it extracts flow information which is used to determine the packets exit port
and QoS requirements. By default, the RS uses application-based forwarding wherein it extracts the complete
application (layer-4) flow from an IP packet. The RS then matches the packet’s flow information against flows found
in the flow table. If a match is found, the packet is forwarded to the output port and transmitted. If a match is not found,
the packet is forwarded to the CPU for additional processing.
To reduce the amount of processing done by the CPU and to use the flow table more efficiently, you can configure the
RS to extract only certain fields from the packet’s L3 header. The RS supports three types of forwarding modes:
•
destination-based
•
host-flow based
•
custom forwarding profile
11.15.1 Configuring Destination-Based and Host-Flow-Based Forwarding
Use the
ip set port forwarding-mode
command to configure the ports on the RS to use either the
destination-based or host-flow-based forwarding mode. These modes determine which fields are extracted from a
packet’s L3 header and used to determine the port list and QoS requirements.
When the RS uses destination-based forwarding, it extracts the destination IP address, TOS, and L4 protocol fields
from IP unicast packets. For multicast packets, the RS extracts the destination IP address, source IP address, TOS, and
L4 protocol fields.
When the RS uses host-flow-based forwarding, it extracts the destination IP address, source IP address, TOS, and L4
protocol fields from the IP packet.
To configure a port’s forwarding mode, enter the following command in Configure mode:.
11.15.2 Configuring a Custom Forwarding Profile
You can configure the RS to use a custom forwarding profile to determine which fields are extracted to identify the
packet’s flow. A custom forwarding profile is used to wildcard specific fields in the IP header.
You can apply a custom forwarding profile to an RS’s slot, then enable it on a per port basis. When you do so, those
ports on which custom forwarding profile is not enabled will use the default forwarding mode.
The fields that can be wild carded are as follows:
•
Source IP Address (SIP)
•
Destination IP Address (DIP)
•
Protocol
•
Source Socket
•
Destination Socket
•
Type of Service (TOS)
To configure a custom forwarding profile, perform the following tasks:
ip set port <port-list> forwarding mode
<destination-based|host-flow-based>