Cisco Nexus 7000 Series - Ipv6 Neighbor Redirect Message

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Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
Chapter 3 Configuring IPv6
Information About IPv6
RAs are also sent in response to router solicitation messages. Router solicitation messages, which have
a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that
the host can immediately auto-configure without needing to wait for the next scheduled RA message.
The source address is usually the unspecified IPv6 address (0:0:0:0:0:0:0:0). If the host has a configured
unicast address, the unicast address of the interface that sends the router solicitation message is used as
the source address in the message. The destination address is the all-routers multicast address with a
scope of the link. When an RA is sent in response to a router solicitation, the destination address in the
RA message is the unicast address of the source of the router solicitation message.
You can configure the following RA message parameters:
• The time interval between periodic RA messages
• The router life-time value, which indicates the usefulness of a router as the default router (for use
by all nodes on a given link)
• The network prefixes in use on a given link
• The time interval between neighbor solicitation message retransmissions (on a given link)
• The amount of time that a node considers a neighbor reachable (for use by all nodes on a given link)
The configured parameters are specific to an interface. The sending of RA messages (with default
values) is automatically enabled on Ethernet interfaces. For other interface types, you must enter the no
ipv6 nd suppress-ra command to send RA messages. You can disable the RA message feature on
individual interfaces by entering the ipv6 nd suppress-ra command.
IPv6 Neighbor Redirect Message
Routers send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a
destination (see Figure 3-14). A value of 137 in the Type field of the ICMP packet header identifies an
IPv6 neighbor redirect message.