CLI Reference Guide-R04

Chapter 31 | IP Interface Commands
IPv6 Interface
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Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
◆ IPv6 Router Advertisements (RA) convey information that enables nodes to
auto-configure on the network. This information may include the default router
address taken from the observed source address of the RA message, as well as
on-link prefix information. However, unintended mis-configurations, or
possibly malicious attacks on the network, may lead to bogus RAs being sent,
which in turn can cause operational problems for hosts on the network.
◆ This command can be used to block RAs and Router Redirect (RR) messages on
the specified interface. Determine which interfaces are connected to known
routers, and enable RA Guard on all other untrusted interfaces.
Example
Console(config)#interface ethernet 1/1
Console(config-if)#ipv6 nd raguard
Console(config-if)#
ipv6 nd
reachable-time
This command configures the amount of time that a remote IPv6 node is
considered reachable after some reachability confirmation event has occurred. Use
the no form to restore the default setting.
Syntax
ipv6 nd reachable-time milliseconds
no ipv6 nd reachable-time
milliseconds - The time that a node can be considered reachable after
receiving confirmation of reachability. (Range: 0-3600000)
Default Setting
30000 milliseconds is used for neighbor discovery operations
0 milliseconds is advertised in router advertisements
Command Mode
Interface Configuration (VLAN)
Command Usage
◆ The time limit configured by this parameter allows the router to detect
unavailable neighbors. During the neighbor discover process, an IPv6 node will
multicast neighbor solicitation messages to search for neighbor nodes. For a
neighbor node to be considered reachable, it must respond to the neighbor
soliciting node with a neighbor advertisement message to become a
confirmed neighbor, after which the reachable timer will be considered in
effect for subsequent unicast IPv6 layer communications.