IP Routing Features
Overview of IP Routing
■ 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.
| ■ If the cache does not contain an entry, 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 five minutes, the software removes the entry. The age timer is not |
| configurable. |
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N o t e | You cannot add static entries to the IP forwarding cache. |
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IP Global Parameters for Routing Switches
The following table lists the IP global parameters and the page where you can find more information about each parameter.
TableParameter | Description | Default | See page |
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Address | A standard IP mechanism that routers use to learn the Media Access | Enabled | |
Resolution | Control (MAC) address of a device on the network. The router sends |
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Protocol (ARP) | the IP address of a device in the ARP request and receives the device’s |
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| MAC address in an ARP reply. |
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ARP age | The amount of time the device keeps a MAC address learned through | 20 minutes | |
| ARP in the device’s ARP cache. The device resets the timer to zero each |
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| time the ARP entry is refreshed and removes the entry if the timer |
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| reaches the ARP age. |
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Proxy ARP | An IP mechanism a router can use to answer an ARP request on behalf | Disabled | |
| of a host. It replies with the router’s own MAC address instead of the |
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| host’s. |
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Time to Live | The maximum number of routers (hops) through which a packet can | 64 hops | |
(TTL) | pass before being discarded. Each router decreases a packet’s TTL by |
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| 1 before forwarding the packet. If decreasing the TTL causes the TTL |
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| to be 0, the router drops the packet instead of forwarding it. |
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Directed | A directed broadcast is a packet containing all ones (or in some cases, | Disabled | |
broadcast | all zeros) in the host portion of the destination IP address. When a router |
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forwarding | forwards such a broadcast, it sends a copy of the packet out each of its |
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| enabled IP interfaces. |
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| Note: You also can enable or disable this parameter on an individual |
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