There is a Possibility That IPv6 Users on the MA5600T Fail to Download Apps

Hello, everyone!

Today, I'd like to share a case with you.

Product Model: SmartAX MA5600T

Problem Description

There is a possibility that IPv6 users on the MA5600T fail to download apps.

Problem Analysis

1. Check the CPU usage of the MPU. It is found that the CPU usage is not high. Therefore, the issue is not caused by high CPU usage.

   

   
   

2. Queried the hardware ARPand ND entries of the device. It was found that about 7K and 3.6K ARP and NDentries were delivered, which occupied most of the specifications. Because the device is configured with the DHCPv6 service, it learns a large number of IPv6 ND entries. An IPv6 entry occupies hardware resources similar to two IPv4 entries. Both IPv4 and IPv6 use the same hardware entry resources.

   

   
   

   Almost 7K ARP entries have been delivered, and 3.6K IPv6 ND entries have been delivered:

   
   

3. When the number of delivered IPv4 and IPv6 address entries reaches the device specification, the subsequent entries fail to be delivered due to hash conflicts. As a result, the app download service of the user through Layer 3 forwarding fails. Error records about IPv6 ND entries failing to be delivered to hardware:

   

   
   

4. Indicates the position where downstream APP download packets are discarded because no IPv6 ND entry is available for forwarding.

   

   
   

Root Cause

The MA5600T learns too many user IPv4 and IPv6 address entries, which is close to the system specification. As a result, subsequent entries fail to be learned due to hash conflicts, and these users cannot download applications through Layer 3 forwarding.

Solution Description

IPv6 addresses occupy twice the hardware entry resources of IPv4 addresses. Therefore, it is recommended that IPv4 addresses be used to allocate IP addresses to users.

I hope it will be helpful for you. Thank you!