Thread network without border routers

[dakhnod]

We are observing that our Thread network falls apart once the only border router leaves.
This leaves us with these questions:

1. Is a border router required in a thread network?
2. Can Thread partitions reunite without any border routers / BBRs?
3. Does the ML-EID change when the Network reforms?
4. Under what conditions does the ML-EID change at all?

Thanks in advance!

[jwhui]

Is a border router required in a thread network?

A router is required, but not a border router.

Can Thread partitions reunite without any border routers / BBRs?

Yes, router-capable devices should join each other and merge partitions.

Does the ML-EID change when the Network reforms?

The Mesh Local Prefix is a configuration included in the Active Operational Dataset. All devices configured to the same Thread Network must be configured with the same Active Operational Dataset.

Under what conditions does the ML-EID change at all?

When the device is configured with a new Active Operational Dataset that has a different Mesh Local Prefix.

[dakhnod]

To my understanding, the ML-EID is an interface address, not just the prefix, right?

So, can the whole address change, despite of the prefix staying the same?

[jwhui]

The Mesh Local Address Interface Identifier is saved in non-volatile storage:

openthread/src/core/thread/mle.cpp

Line 482 in f6cee79

networkInfo.SetMeshLocalIid(mMeshLocalEid.GetAddress().GetIid());

And restored from non-volatile storage:

openthread/src/core/thread/mle.cpp

Line 416 in f6cee79

mMeshLocalEid.GetAddress().SetIid(networkInfo.GetMeshLocalIid());

[dakhnod]

What would you recommend as address that is tied to the device, not the network?
Something routable that doesn't change with a new network?

[jwhui]

I generally recommend against relying on hard-coded IP addresses.

That said, the ML-EID should be stable unless you explicitly change the Mesh Local Prefix configuration. However, the ML-EID is only routable within a Thread mesh.

[dakhnod]

Thanks!

Here are the addresses of my interface:

wpan0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1280
        1. inet6 fdb7:5552:f959:a347:0:ff:fe00:fc11  prefixlen 64  scopeid 0x0<global>
        2. inet6 fdf5:e082:23:1:90c9:7ddb:3482:f0ae  prefixlen 64  scopeid 0x0<global>
        3. inet6 fdb7:5552:f959:a347:0:ff:fe00:c00  prefixlen 64  scopeid 0x0<global>
        4. inet6 fdb7:5552:f959:a347:0:ff:fe00:fc10  prefixlen 64  scopeid 0x0<global>
        5. inet6 fe80::c8e4:3d1:99a6:7688  prefixlen 64  scopeid 0x20<link>
        6. inet6 fdb7:5552:f959:a347:3d52:a887:4c21:66ef  prefixlen 64  scopeid 0x0<global>
        7. inet6 fdb7:5552:f959:a347:0:ff:fe00:fc38  prefixlen 64  scopeid 0x0<global>

I assume that 5 is link-local, but what are the rest?
How can I identify the address type?
Is there an ot-ctl command that shows the type, along with the addresses?

[jwhui]

See the ipaddr CLI command.

[dakhnod]

Thank you!