Working mechanism and principle of IPv6 Neighbor Discovery

Technorati labels: IPv6, IPv6 neighbor discovery

IPv6 Neighbor Discovery and static neighbor designation

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The topology graph still displays the static and manually configured global unicast address and link-local address.

So what is IPv6 neighbor discovery?

There is a command:

Show ipv6 neighbor

First, on R1, show ipv6 neighbor. It must be directly connected to R2.

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When I first read it, I was wrong. Haha, ca01.1a44.0008 is R2, and R1 is started with ca00.

So here, the neighbor we see on the router is actually the link-local address of the directly connected device. It is definitely not the unicast address configured for the interface address 2012: 2/64.

Let's take a look at the R2 and the R1 and R3 neighbors on both sides.

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Meanings of parameters:

Age:I understand the IPv6 lifecycle as a timer. It is a bit similar to arp. After aging, the system will trigger re-sending the UPDATE message to maintain the neighbor relationship. However, the Unit here is minute. Then the timer is incremented by 1.

Link-layer addr:It can be seen at a glance that it is a MAC address of the peer directly connected to the neighbor. 48 bits, the same as IPv4.

Status:The REACH status indicates that the neighbor is reachable. The STALE status (default) means that the neighbor cannot be reached within the last 30 minutes.

Interface:Outbound interface. The interface from which the peer address is learned.

There is another problem,CiscoYou can add static neighbor table items to the neighbor discovery table on the vro..

The question is, why is this feature available? What are the requirements behind this function?

CISCO implements the Add static neighbor table item, because most IPv6 traffic generation devices cannot correctly support IPv6 NDP. if no neighbor table is created in the Neighbor Discovery table, IPv6 traffic cannot be forwarded through the router. This function is necessary for compatibility and fault tolerance.

Run the IPv6 neighbor command to add a static table entry neighbor.

Router # Ipv6 neighbor IPv6-address interface hw-address

PS: this command is used globally.

Since it is a static table item, the device must passively know this information.

On R1, there is already an R2 as its neighbor, but the network type is not a point-to-point type.

So I want to add as many as possible, even if the neighbor I added does not exist.

In R1 before adding a neighbor:

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After adding static neighbors:

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I configured a static neighbor in the global environment. Then show ipv6 neighbors. The static neighbor that is configured immediately is already in my ipv6 neighbor list. age is-, indicating that it will never age, because it is my static configuration. Status, REACH, reachable.

Here I do not know why it is reachable, But what mechanism is used to ensure it is reachable.

It is also possible that cisco is reachable by default when developing ios. Let's take a look at the ping results below, all of which are RTO.

In fact, this static neighbor is not reachable.

Each vendor has different implementation methods. I have also verified them here.

The maipu router checks whether the peer end is reachable. If the configuration is not reachable, it does not write data to the neighbor table.

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Because I cannot find it on the Internet, cisco is a default behavior. There is no more special significance.

This article is from the "thank-me, only focus on the principle" blog, please be sure to keep this source http://361531.blog.51cto.com/351531/636282