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| Patch Release Note |
| Table 9: Router Discovery Process |
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| When ... | Then ... |
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| Router Discovery advertising starts on a | the router multicasts a router advertisement |
| router interface because: | and continues to multicast them periodically |
| - the router starts up, or | until router advertising is disabled. |
-advertisements are enabled on the switch or on an interface
a host starts up | the host may send a router solicitation |
| message. |
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the router receives a router solicitation | the router multicasts an early router |
| advertisement on the multicast interface on |
| which it received the router solicitation. |
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a host receives a router advertisement | the host stores the IP address and preference |
| level for the advertisement lifetime. |
the lifetime of all existing router advertisements on a host expires
the host sends a router solicitation.
a host does not receive a router | the host waits for the next unsolicited router |
advertisement after sending a small number | advertisement |
of router solicitations |
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a host needs a default router address | the host uses the IP address of the router or |
| L3 switch with the highest preference level. |
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Router Discovery advertising is deleted from | the router multicasts a router advertisement |
the physical interface (DELETE IP ADVERTISE | with the IP address(es) that stopped |
command), or the logical interface has | advertising, and a lifetime of zero (0). It |
ADVERTISE set to NO (SET IP INTERFACE | continues to periodically multicast router |
command) | advertisements for other interfaces. |
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the router receives a router advertisement | the router does nothing but silently discards |
from another router | the message. |
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Router Advertisement Messages
Router Solicitation Messages
A router advertisement is an ICMP (type 10) message containing:
■In the destination address field of the IP header, the interface's configured advertisement address, either 224.0.0.1 (ALL) or 255.255.255.255 (LIMITED).
■In the lifetime field, the interface's configured advertisement lifetime.
■In the Router Address and Preference Level fields, the addresses and preference levels of all the logical interfaces that are set to advertise.
A router solicitation is an ICMP (type 10) message containing:
■Source Address: an IP address belonging to the interface from which the message is sent
■Destination Address: the configured Solicitation Address, and
■
Router Advertisement The router advertisement interval is the time between router advertisements. Interval For the first few advertisements sent from an interface (up to 3), 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
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