Ip route table, Ip forwarding cache – Brocade BigIron RX Series Configuration Guide User Manual
Page 236
158
BigIron RX Series Configuration Guide
53-1002484-04
The IP packet flow
7
IP Route table
The IP route table contains paths to IP destinations.
The IP route table can receive the paths from the following sources:
•
A directly-connected destination, which means there are no router hops to the destination
•
A static IP route, which is a user-configured route
•
A route learned through RIP
•
A route learned through OSPF
•
A route learned through BGP4
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 – 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 Layer 2,
Layer 3 and TCP/UDP information.
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
“Displaying the IP route table”
To configure a static IP route, refer to
To clear a route from the IP route table, refer to
To increase the size of the IP route table for learned and static routes, refer to
modifying system parameter default settings”
•
For learned routes, modify the ip-route parameter.
•
For static routes, modify the ip-static-route parameter.
IP forwarding cache
The device maintains a software cache table for fast processing of IP packets that are forwarded or
generated by the CPU. The cache also contains forwarding information that is normally contained in
the IP routing table. For example, the cache contains information on the physical outgoing port,
priority, VLAN, and the type of cache entry. Also, cache entries have hardware information, which is
useful for debugging and aging.
Destination NetMask Gateway Port Cost Type
1.1.0.0 255.255.0.0 99.1.1.2 1/1 2 R