Ip forwarding cache – Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) User Manual
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Brocade Virtual ADX Switch and Router Guide
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Overview
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A directly-connected destination, which means there are no router hops to the destination
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A static IP route, which is a user-configured route
The IP route table contains the best path to a destination.
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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 – 255.
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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’s 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’s 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 the following:
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To configure a static IP route, refer to the following:
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To clear a route from the IP route table, refer to the following:
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For learned routes, modify the ip-route parameter.
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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’s destination.
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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’s final destination. The port numbers are the ports through which
the destination can be reached.
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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
2 R