Dell Brocade DCX, Configuration Manual

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BigIron RX Series Configuration Guide 149
53-1001810-01
Basic IP parameters and defaults
7
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.
There are two types of IP cache entries.
1. Directly connected host entries – These entries are created when the CPU receives the first
packet destined to a directly connected host. Host entries are set to age out after a certain
period if no traffic is seen for that entry.
2. Network entries – These entries are created when a route table entry is created in software.
These entries are not subjected to aging. A route table entry is created when routes are
learned by routing protocols such as OSPF or when routes are statically configured.
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 device 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 219.
Basic IP parameters and defaults
IP is enabled by default. The following protocols are disabled by default:
•
Route exchange protocols (RIP, OSPF, BGP4)
•
Multicast protocols (IGMP, PIM-DM, PIM-SM, DVMRP)
•
Router redundancy protocols (VRRPE, VRRP, FSRP)
When parameter changes take effect
Most IP parameters described in this chapter are dynamic. They take effect immediately, as soon
as you enter the CLI command. You can verify that a dynamic change has taken effect by
displaying the running configuration. To display the running configuration, enter the show
running-config or write terminal command at any CLI prompt.
To save a configuration change permanently so that the change remains in effect following a
system reset or software reload, save the change to the startup configuration file. Enter the write
memory command from the Privileged EXEC level of any configuration level of the CLI.
Changes to memory allocation require you to reload the software after you save the changes to the
startup configuration file. When reloading the software is required to complete a configuration
change, the procedure that describes the configuration change includes a step for reloading the
software.
IP Address Next Hop MAC Type Port Vlan Pri
1 192.168.1.11 DIRECT 0000.0000.0000 PU n/a 0