Bug #8925


IPv6 RA Prefix Doesn't Match Interface Prefix ID

Added by Allen Balaj almost 4 years ago. Updated almost 4 years ago.

Not a Bug
IPv6 Router Advertisements (RADVD)
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To summarize:

I have one WAN and one LAN interface. The LAN (igb) interface also has an OPT interface for VLAN 2 named GUESTVLAN (opt1), which is set to track the WAN interface with prefix ID 2. The WAN interface is configured for DHCPv6 and to request a prefix of size /60.
Router advertisements are configured for both LAN subnets. In the LAN subnet, I can see a DNS server being advertised with a prefix ending in 0, and in the GUESTVLAN subnet, I can see a DNS server being advertised with a prefix ending in 2, as expected.

However, the problem is that both subnets are advertising the same address prefix for use via SLAAC. I first confirmed this with Wireshark, and then I loaded /var/etc/radvd.conf and saw that the router advertisement daemon is set to advertise the same prefix on both networks. I'm including a copy of the automatically generated config file here.


radvd.conf.txt (1.08 KB) radvd.conf.txt Allen Balaj, 09/21/2018 12:15 AM
radvd.conf (1.67 KB) radvd.conf Jim Pingle, 09/22/2018 12:10 PM
Actions #1

Updated by Jim Pingle almost 4 years ago

I can't reproduce this here. I have three local interfaces all set to track WAN with index 0, 1, 2 from a /60 delegation. All of them have the correct and expected (different) prefixes. See attached.

There must be something different about your environment or settings at play here. Please start a forum post with more detail about your configuration/setup, specifically the exact values used on the interfaces and in the DHCPv6/RA server settings.

Be sure you are on the latest 2.4.4 RC when testing, and after making any change to a tracking interface, save/apply on WAN or reboot and see if the configuration remains incorrect.

If, after discussing the problem in more detail, we find a bug here this can be reopened.

Actions #2

Updated by Allen Balaj almost 4 years ago

Hi Jim,

Thanks for taking the time to try and reproduce this issue. I did create a forum issue last week (found here:, but didn't receive any meaningful feedback. I have updated the post with the additional information that you requested, however.

I can confirm that issue occurs on the latest version of 2.4.4, as well as 2.4.3 and 2.4.2. I did not test this on versions earlier than that, but it has been happening for some time and I only just recently decided to investigate further.

Once the issue has been discussed further in the forum, would you prefer that I create a new bug for this issue, or post in this bug tracker thread requesting that this specific issue be reopened?

Thanks again,



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