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Basic IPv6 questions - 1

Latest reply: Feb 21, 2020 14:29:30 281 1 4 0 2

Hello all,

 I'd like to share with you some basic IPv6 questions.

1. Is a License Required for IPv6?

A: Modular switches require the license, but fixed switches do not.

The license control items for IPv6 are as follows:


2. How Do I Configure an IPv6 Address?

A: Enable IPv6 in the system view and then configure ipv6 addresses on the interface:

<HUAWEI> system-view

[HUAWEI] ipv6

[HUAWEI] interface gigabitethernet 0/0/1

[HUAWEI-GigabitEthernet0/0/1] ipv6 enable

[HUAWEI-GigabitEthernet0/0/1] ipv6 address fc00::1/64

3. What Are the Precautions for Configuring an IPv6 Address for a Sub-interface?

A:  The ipv6 nd ns multicast-enable command which is similar to the arp broadcast enable command need to be configured on the sub-interface. If this command is not run, the device cannot actively learn ND entries by sending NS packets. Instead, the device passively learns ND entries by receiving NA packets sent by other devices.


4. Do Switches Support IPv4/IPv6 Dual Stack?

A: Yes.


5. How Can I Check Whether the IPv6 Protocol on an Interface Is Up?

A: Run the display ipv6 interface brief command.


6. How Do I Check the Routing Table and FIB Table of IPV6?

A: For routing table: display ipv6 routing-table.

You can run the display ipv6 routing-table XX::XX command to check a specific route.



For FIB entries: display ipv6 fib

The display ipv6 fib X:X::X:X command is used to view a specific entry. Note: If the slot ID is not specified, the output is the FIB of the MPU.

Run the display ipv6 fib slot-id and display ipv6 fib slot-id X:X::X:X commands to check the FIB of the LPU.

Example: To query the FIB of slot 1.


7. How Can I Determine the Number of IPv6 FIB Entries on an LPU?

A: display ipv6 fib [ slot-id ] statistics  all



The value 129024 indicates the IPv6 FIB specification of the slot 1, and the value 10 indicates the number of FIB entries used on slot 1. Note: Check the Prefix Count instead of Entry Count. For example, if a route has two next hops, it is counted as a FIB, but counted as two entries.

8. How Do I Determine Whether the Number of IPv6 FIB Entries on an LPU of a Modular Switch Exceeds the Upper Limit?

A: Check the number of IPv6 FIB entries of the MPU. 


Check the number of IPv6 FIB entries of the LPU. (The number 1 following fib indicates the slot number.)



If the number of FIB entries of the MPU is greater than that of the LPU, the number of FIB entries exceeds the specification.

If the number of IPv6 FIB entries does not exceed the specification, the LPU is in the normal state. If the number of IPv6 FIB entries exceeds the specification, the LPU is in the overload state.


Note: When the LPU is in the overload state and the number of IPv6 FIB entries on the LPU returns to the normal range, the overload state needs to be manually cleared.

[huawei]recover ipv6 fib overload forward slot  slot-id

9. How Can I Determine Whether an IPv6 FIB Entry Is Delivered to an LPU When the Number of FIB Entries Exceeds the Upper Limit?

A: Run the display ipv6 fib X:X::X:X and display ipv6 fib slot-id X:X::X:X commands.

Check whether the same FIB entry is matched. If so, the FIB entry is delivered successfully. If not, the FIB entry is not delivered to the LPU.

Note: When the specifications are exceeded, some routes cannot be delivered to the LPU, which may cause the traffic that should be forwarded through the specific route may incorrectly match the route with a smaller mask or the default route. As a result,  packets are forwarded through an incorrect outbound interface. 

10. How Do I Restore Services When the Number of FIB Entries Restores to the Normal Value After the Number of FIB Entries Exceeds the Upper Limit?

A: [huawei]refresh  ipv6  fib  slot slot-id

Note: Refreshing FIB entries does not affect services. However, refresh FIB entries only after the number of FIB entries is restored to a value within the upper limit.

After the refresh operation is performed, clear the overload status.

[huawei]recover ipv6 fib overload forward slot slot-id

This command is used to clear the status, which does not affect services.

The next post: Basic IPv6 questions 2

I hope it is of help to you.

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Created Feb 21, 2020 14:29:30

good job
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