Patch | SHOW IP ADVERTISE | 55 | |
| Table 10: Parameters displayed in the output of the SHOW IP ADVERTISE |
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| command. (Continued) |
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| Parameter | Meaning |
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| IP Address | An IP address assigned to the interface. |
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| Advertise | Whether the address for this logical interface should | |
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| be advertised. |
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| Preference Level | The preferability of the address as a default router |
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| address relative to other router addresses on the |
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| same subnet. |
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See Also DISABLE IP DISCOVERY
DELETE IP DISCOVERY INTERFACE
ENABLE IP DISCOVERY
ADD IP DISCOVERY INTERFACE
SET IP DISCOVERY INTERFACE
Old Router Discover Before an IP host can send IP packets, it needs the IP address of a router that Process can forward it to its destination. When router advertisements are enabled, the
router multicasts router advertisements periodically on any interfaces that are configured to advertise. When hosts receive these messages, they store them for the specified lifetime. They forward traffic to the IP address of the router with the highest preference level specified in the router advertisement.
When a host first starts up, it may send one, or a small number of router solicitations to prompt a quicker router advertisement, instead of waiting for the next router advertisement to arrive automatically. When the router receives a router solicitation with an IP address, it immediately multicasts an early router advertisement.
For the first few advertisements sent from an interface (up to 3), if the randomly chosen interval is greater than 16 seconds, the router sends the router advertisements at intervals of at most 16 seconds. After these initial transmissions, it sends router advertisements at random intervals between the minimum and maximum intervals that the user configures, to reduce the probability of synchronization with the advertisements from other routers on the same link.
If either an interface, or router advertisements on an interface are disabled, the router sends a final multicast advertisement on the interface with a lifetime field of zero. If some of the IP addresses have advertising disabled, while others continue to advertise, the router sends a router advertisement containing the remaining IP addresses.
The router does not behave as a Router Discovery host to discover other routers on the LAN; it discards any router advertisements that it receives from other routers.
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