Ip forwarding cache – Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 User Manual
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Brocade ICX 6650 Layer 3 Routing Configuration Guide
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IP configuration overview
The IP route table contains the best path to a destination:
•
When the software receives paths from more than one of the sources listed above, the
software compares the administrative distance of each path and selects the path with the
lowest administrative distance. The administrative distance is a protocol-independent value
from 1 through 255.
•
When the software receives two or more best paths from the same source and the paths have
the same metric (cost), the software can load share traffic among the paths based on
destination host or network address (based on the configuration and the Layer 3 Switch
model).
Here is an example of an entry in the IP route table.
Each IP route table entry contains the destination IP address and subnet mask and the IP address
of the next-hop router interface to the destination. Each entry also indicates the port attached to
the destination or the next-hop to the destination, the route IP metric (cost), and the type. The type
indicates how the IP route table received the route:
•
To display the IP route table, refer to
“Displaying the IP route table”
on page 122 (Layer 3
Switch only).
•
To configure a static IP route, refer to
on page 45 (Layer 3 Switch
only).
•
To clear a route from the IP route table, refer to
on page 124 (Layer 3
Switch only).
•
To increase the size of the IP route table for learned and static routes, refer to the section
“Displaying and modifying system parameter default settings” section in the Brocade ICX 6650
Platform and Layer 2 Switching Configuration Guide:
-
For learned routes, modify the ip-route parameter.
-
For static routes, modify the ip-static-route parameter.
IP forwarding cache
The IP forwarding cache provides a fast-path mechanism for forwarding IP packets. The cache
contains entries for IP destinations. When a Brocade Layer 3 Switch has completed processing and
addressing for a packet and is ready to forward the packet, the device checks the IP forwarding
cache for an entry to the packet destination:
•
If the cache contains an entry with the destination IP address, the device uses the information
in the entry to forward the packet out the ports listed in the entry. The destination IP address is
the address of the packet final destination. The port numbers are the ports through which the
destination can be reached.
•
If the cache does not contain an entry and the traffic does not qualify for an entry in the
session table instead, the software can create an entry in the forwarding cache.
Each entry in the IP forwarding cache has an age timer. If the entry remains unused for ten
minutes, the software removes the entry. The age timer is not configurable.
Here is an example of an entry in the IP forwarding cache.
Destination NetMask Gateway Port Cost Type
10.1.0.0 255.255.0.0 10.1.1.2 1/1/1 2 R