OpenThread
No Mesh Local address on Wifi network #7698
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Hi, If I use my Home wifi connection, I can see that my smartphone receives IPV4 addresses and Link Local IPV6 addresses (starting with fe80). As per my understanding of https://openthread.io/guides/thread-primer/ipv6-addressing, these Link Local IPV6 addresses are not suitable for a communication between the smartphone (on wifi network) and a Thread device (on Thread network) because such Link Local address will not be routed by the Open Thread Border Router. A packet sent on Thread network by a Thread device will not be able to reach a smartphone which is on Wifi network. To achieve this, I need a Mesh Local or global address. I have an alternate solution using my cell phone. With that solution, I use 2 smartphones:
How are we supposed to handle the first case where the Wifi network only gives Link Local IPV6 addresses? Thank you! |
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Replies: 1 comment 6 replies
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An IPv6 router on the network needs to advertise a routable IPv6 prefix that allows Wi-Fi and Thread devices to communicate with each other. The default OpenThread Border Router configuration should automatically detect if there are no existing IPv6 routers on the Wi-Fi network and start advertising its own routable IPv6 prefix on the Wi-Fi network. The Thread Border Router - Bidirectional IPv6 Connectivity and DNS-Based Service Discovery guide should demonstrate this behavior. If you use tcpdump to capture IPv6 packets on the Wi-Fi network, you should see ICMPv6 Router Advertisement messages being sent on the WI-Fi network. |
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Yes, you can find the routable IPv6 address of the smartphone with the Network Analyzer App mentioned in https://openthread.io/codelabs/openthread-border-router#6. Then can ping the smartphone directly from the end device with the OT CLI |
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As per my first message, at the top of this thread, what you say works fine when I use a smartphone configured in Wifi Access Point (receiving data from 4G network). |
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A Thread Border Router will send IPv6 Router Advertisement messages to config routable IPv6 addresses on all Wi-Fi devices in the same Wi-Fi network if it finds out that there is no IPv6 service provided in the Wi-Fi network. It means once you set up a Thread Border Router in your Wi-Fi network, there will always be routable IPv6 addresses on your smartphone. See https://datatracker.ietf.org/doc/html/rfc4862 and https://datatracker.ietf.org/doc/html/rfc4861 for backgrounds how the "routable" addresses are being configured. |
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Note that if your smartphone can send packets to the Thread device, the smartphone already has a routable IPv6 address (which it includes in the IPv6 Source Address field of packets sent to the Thread device).
As mentioned in #7698 (comment), the border router sends ICMPv6 Router Advertisement messages with a Prefix Information Option allowing the smartphone to self-configure a routable IPv6 address. |
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Thank you very much! |
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An IPv6 router on the network needs to advertise a routable IPv6 prefix that allows Wi-Fi and Thread devices to communicate with each other. The default OpenThread Border Router configuration should automatically detect if there are no existing IPv6 routers on the Wi-Fi network and start advertising its own routable IPv6 prefix on the Wi-Fi network. The Thread Border Router - Bidirectional IPv6 Connectivity and DNS-Based Service Discovery guide should demonstrate this behavior.
If you use tcpdump to capture IPv6 packets on the Wi-Fi network, you should see ICMPv6 Router Advertisement messages being sent on the WI-Fi network.