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PowerConnect B-Series FCX Configuration Guide 789
53-1002266-01
Overview
26
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 878 (Layer 3
Switch only).
• To configure a static IP route, refer to “Configuring static routes” on page 819 (Layer 3 Switch
only).
• To clear a route from the IP route table, refer to “Clearing IP routes” on page 880 (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” on page 321:
- 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 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.
Each IP forwarding cache entry contains the IP address of the destination, and the IP address and
MAC address of the next-hop router interface to the destination. If the destination is actually an
interface configured on the Layer 3 Switch itself, as shown here, then next-hop information
indicates this. The port through which the destination is reached is also listed, as well as the VLAN
and Layer 4 QoS priority associated with the destination if applicable.
To display the IP forwarding cache, refer to “Displaying the forwarding cache” on page 877.
Destination NetMask Gateway Port Cost Type
1.1.0.0 255.255.0.0 99.1.1.2 1/1 2 R
IP Address Next Hop MAC Type Port Vlan Pri
1 192.168.1.11 DIRECT 0000.0000.0000 PU n/a 0