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The IPv6 Redirect Messages feature enables a device to send Internet Control Message Protocol (ICMP) IPv6 neighbor redirect messages to inform hosts of better first-hop nodes (devices or hosts) on the path to a destination.
A value of 137 in the type field of the ICMP packet header identifies an IPv6 neighbor redirect message. Devices send neighbor redirect messages to inform hosts of better first-hop nodes on the path to a destination (see the figure below).
Note | A device must be able to determine the link-local address for each of its neighboring devices in order to ensure that the target address (the final destination) in a redirect message identifies the neighbor device by its link-local address. For static routing, the address of the next-hop device should be specified using the link-local address of the device; for dynamic routing, all IPv6 routing protocols must exchange the link-local addresses of neighboring devices. |
After forwarding a packet, a device should send a redirect message to the source of the packet under the following circumstances:
The destination address of the packet is not a multicast address.
The packet was not addressed to the device.
The packet is about to be sent out the interface on which it was received.
The device determines that a better first-hop node for the packet resides on the same link as the source of the packet.
The source address of the packet is a global IPv6 address of a neighbor on the same link, or a link-local address.
Use the ipv6 icmp error-interval command to limit the rate at which the device generates all IPv6 ICMP error messages, including neighbor redirect messages, which ultimately reduces link-layer congestion.
Note | A device must not update its routing tables after receiving a neighbor redirect message, and hosts must not originate neighbor redirect messages. |
1.
enable
2.
show
ipv6
interface
[brief] [type
number] [prefix]
3.
show
ipv6
neighbors
[interface-type
interface-number [
ipv6-address |
ipv6-hostname ]
|
statistics]
4.
show
ipv6
route
[ipv6-address |
ipv6-prefix/prefix-length |
protocol |
interface
interface-type
interface-number]
5.
show
ipv6
traffic
[
interface
interface-type
interface-number]
6.
show
hosts
[vrf
vrf-name |
all |
hostname |
summary]
7.
enable
8.
show
running-config
In the following example, the show ipv6 interface command is used to verify that IPv6 addresses are configured correctly for GigabitEthernet interface 0/0/0. Information is also displayed about the status of IPv6 neighbor redirect messages, IPv6 neighbor discovery messages, and stateless autoconfiguration.
Device# show ipv6 interface gigabitethernet 0/0/0 GigabitEthernet0/0/0 is up, line protocol is up IPv6 is stalled, link-local address is FE80::1 Global unicast address(es): 2001:DB8:2000::1, subnet is 2001:DB8:2000::/64 2001:DB8:3000::1, subnet is 2001:DB8:3000::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:1 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds ND advertised reachable time is 0 milliseconds ND advertised retransmit interval is 0 milliseconds ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds Hosts use stateless autoconfig for addresses.
Related Topic |
Document Title |
---|---|
IPv6 addressing and connectivity |
IPv6 Configuration Guide |
Cisco IOS commands |
|
IPv6 commands |
Cisco IOS IPv6 Command Reference |
Cisco IOS IPv6 features |
Standard/RFC |
Title |
---|---|
RFCs for IPv6 |
IPv6 RFCs |
MIB |
MIBs Link |
---|---|
|
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |