When executing a UDP to the mle-eid IP, a "No Route" error occurred.

[jiemincao]

When using the UDP, the leader discovered that certain routes were unreachable. After checking the logs, a "No Route" error was found. Upon further investigation, it was determined that when a child switches to a new parent, its router information is not updated in the leader's EID Cache Table, causing this issue.

The currently known solution is to have the child send a UDP to the leader, which triggers the leader to update its EID Cache Table. However, if no IP message is received from the child, the leader will continue to drop packets. It is unclear whether there are other possible solutions.

We are currently using the Thread Reference version 2023-07-06. Has this issue been resolved in a newer version?

The log is as follows:
[N] MeshForwarder-: Dropping IPv6 UDP msg, len:57, chksum:7258, ecn:no, sec:yes, error:NoRoute, prio:normal
[N] MeshForwarder-: src:[fd00:db8:0:0:0:ff:fe00:fc00]:5683
[N] MeshForwarder-: dst:[fd00:db8:0:0:0:0:0:104]:5683

[aaa147147]

I have encountered this problem before, and updating to the latest version looks much more stable. I suggest you update to the latest version.
And it is also best to update the Openthread version of Thread devices to the latest version

[jiemincao]

Thank you for the response. I will proceed with the update and testing.

[jiemincao]

Hi:
After the update, the previous "No Router" issue is no longer occurring, but a new issue has arisen. After the network is set up, some routers are not directly connected to the leader, even though their signal is strong. In the leader's router table, these routers are shown as "not directly connected" to the leader, but on these routers' end, they show that they can directly connect to the leader. This causes the data they send to be lost due to the leader's MAC address.

leader:
| ID | RLOC16 | Next Hop | Path Cost | LQ In | LQ Out | Age | Extended MAC | Link |
+----+--------+----------+-----------+-------+--------+-----+------------------+------+
| 0 | 0x0000 | 29 | 1 | 3 | 3 | 18 | 00000000000000dc | 1 |
| 4 | 0x1000 | 13 | 1 | 3 | 3 | 53 | 00000000000000ea | 1 |
| 5 | 0x1400 | 40 | 1 | 3 | 3 | 15 | 000000000000008f | 1 |
| 8 | 0x2000 | 55 | 1 | 3 | 3 | 27 | 00000000a0780036 | 1 |
| 12 | 0x3000 | 27 | 1 | 3 | 3 | 20 | 000000000000010b | 1 |
| 13 | 0x3400 | 27 | 1 | 3 | 3 | 23 | 00000000000000cb | 1 |
| 14 | 0x3800 | 13 | 1 | 3 | 3 | 23 | 00000000000000b8 | 1 |
| 15 | 0x3c00 | 47 | 1 | 3 | 3 | 13 | 000000000000009f | 1 |
| 16 | 0x4000 | 12 | 1 | 3 | 3 | 14 | 000000000000008b | 1 |
| 18 | 0x4800 | 63 | 0 | 0 | 0 | 0 | 503832333245a638 | 0 |
| 24 | 0x6000 | 35 | 1 | 3 | 3 | 26 | 00000000a0780094 | 1 |
| 27 | 0x6c00 | 47 | 1 | 3 | 3 | 16 | 0000000000000101 | 1 |
| 28 | 0x7000 | 55 | 1 | 0 | 0 | 203 | 00000000a0780132 | 0 |
| 29 | 0x7400 | 15 | 1 | 3 | 3 | 25 | 00000000000000b5 | 1 |
| 31 | 0x7c00 | 43 | 1 | 3 | 3 | 44 | 00000000a0780089 | 1 |
| 33 | 0x8400 | 27 | 1 | 3 | 3 | 52 | 00000000a0780149 | 1 |
| 35 | 0x8c00 | 14 | 1 | 3 | 3 | 26 | 00000000a0780080 | 1 |
| 37 | 0x9400 | 14 | 1 | 3 | 3 | 26 | 00000000a0780086 | 1 |
| 40 | 0xa000 | 0 | 1 | 3 | 3 | 25 | 0000000000000085 | 1 |
| 41 | 0xa400 | 14 | 1 | 3 | 3 | 56 | 00000000000000c2 | 1 |
| 43 | 0xac00 | 35 | 1 | 3 | 3 | 25 | 00000000000000b9 | 1 |
| 44 | 0xb000 | 35 | 1 | 3 | 3 | 27 | 00000000000000cf | 1 |
| 45 | 0xb400 | 15 | 1 | 3 | 3 | 28 | 00000000000000cd | 1 |
| 47 | 0xbc00 | 13 | 1 | 3 | 3 | 12 | 00000000000000b6 | 1 |
| 48 | 0xc000 | 15 | 1 | 3 | 3 | 18 | 00000000a0780084 | 1 |
| 50 | 0xc800 | 35 | 1 | 3 | 3 | 14 | 00000000a0780096 | 1 |
| 52 | 0xd000 | 15 | 1 | 3 | 3 | 200 | 00000000a0780098 | 1 |
| 54 | 0xd800 | 14 | 1 | 3 | 3 | 23 | 0000000000000093 | 0 |
| 55 | 0xdc00 | 27 | 1 | 3 | 3 | 20 | 00000000000000f9 | 1 |
| 57 | 0xe400 | 14 | 1 | 3 | 3 | 20 | 00000000000000bb | 1 |
| 59 | 0xec00 | 35 | 1 | 3 | 3 | 13 | 00000000000000d1 | 0 |

leader received ec00 adv RSSI:
[I] MeshForwarder-: Received IPv6 UDP msg, len:120, chksum:e7a0, ecn:no, from:00000000000000d1, sec:no, prio:net, rss:-21.0
[I] MeshForwarder-: src:[fe80:0:0:0:200:0:0:d1]:19788
[I] MeshForwarder-: dst:[ff02:0:0:0:0:0:0:1]:19788
[I] Mle-----------: Receive Advertisement (fe80:0:0:0:200:0:0:d1,0xec00)

ec00 router:
| ID | RLOC16 | Next Hop | Path Cost | LQ In | LQ Out | Age | Extended MAC | Link |
+----+--------+----------+-----------+-------+--------+-----+------------------+------+
| 0 | 0x0000 | 29 | 1 | 3 | 3 | 9 | 00000000000000dc | 1 |
| 4 | 0x1000 | 35 | 1 | 3 | 3 | 1 | 00000000000000ea | 1 |
| 5 | 0x1400 | 18 | 1 | 3 | 3 | 5 | 000000000000008f | 1 |
| 8 | 0x2000 | 55 | 1 | 3 | 3 | 13 | 00000000a0780036 | 1 |
| 12 | 0x3000 | 27 | 1 | 3 | 3 | 3 | 000000000000010b | 1 |
| 13 | 0x3400 | 27 | 1 | 3 | 3 | 44 | 00000000000000cb | 1 |
| 14 | 0x3800 | 13 | 1 | 3 | 3 | 5 | 00000000000000b8 | 1 |
| 15 | 0x3c00 | 18 | 1 | 3 | 3 | 6 | 000000000000009f | 0 |
| 16 | 0x4000 | 18 | 1 | 3 | 3 | 12 | 000000000000008b | 1 |
| 18 | 0x4800 | 27 | 1 | 3 | 3 | 2 | 503832333245a638 | 1 |
| 24 | 0x6000 | 54 | 1 | 0 | 0 | 89 | 00000000a0780094 | 0 |
| 27 | 0x6c00 | 57 | 1 | 3 | 3 | 45 | 0000000000000101 | 1 |
| 28 | 0x7000 | 55 | 1 | 3 | 3 | 45 | 00000000a0780132 | 1 |
| 29 | 0x7400 | 14 | 1 | 3 | 3 | 7 | 00000000000000b5 | 1 |
| 31 | 0x7c00 | 54 | 1 | 3 | 3 | 36 | 00000000a0780089 | 0 |
| 33 | 0x8400 | 48 | 1 | 3 | 3 | 8 | 00000000a0780149 | 1 |
| 35 | 0x8c00 | 13 | 1 | 3 | 3 | 30 | 00000000a0780080 | 1 |
| 37 | 0x9400 | 57 | 1 | 3 | 3 | 12 | 00000000a0780086 | 1 |
| 40 | 0xa000 | 18 | 1 | 3 | 3 | 34 | 0000000000000085 | 1 |
| 41 | 0xa400 | 14 | 1 | 3 | 3 | 6 | 00000000000000c2 | 1 |
| 43 | 0xac00 | 13 | 1 | 3 | 3 | 9 | 00000000000000b9 | 0 |
| 44 | 0xb000 | 35 | 1 | 3 | 3 | 7 | 00000000000000cf | 0 |
| 45 | 0xb400 | 18 | 1 | 3 | 3 | 4 | 00000000000000cd | 1 |
| 47 | 0xbc00 | 13 | 1 | 3 | 3 | 25 | 00000000000000b6 | 0 |
| 48 | 0xc000 | 4 | 1 | 3 | 3 | 12 | 00000000a0780084 | 1 |
| 50 | 0xc800 | 35 | 1 | 3 | 3 | 9 | 00000000a0780096 | 1 |
| 52 | 0xd000 | 18 | 1 | 0 | 0 | 42 | 00000000a0780098 | 0 |
| 54 | 0xd800 | 14 | 1 | 3 | 3 | 3 | 0000000000000093 | 1 |
| 55 | 0xdc00 | 35 | 1 | 3 | 3 | 5 | 00000000000000f9 | 1 |
| 57 | 0xe400 | 13 | 1 | 3 | 3 | 30 | 00000000000000bb | 1 |
| 59 | 0xec00 | 63 | 0 | 0 | 0 | 0 | 00000000000000d1 | 0 |

Reason for lost:
[I] Mac-----------: Frame rx failed, error:UnknownNeighbor, len:124, seqnum:172, type:Data, src:0xec00, dst:0x4800, sec:yes, ackreq:yes
[I] Mac-----------: Frame rx failed, error:UnknownNeighbor, len:50, seqnum:173, type:Data, src:0xec00, dst:0x4800, sec:yes, ackreq:yes

[jwhui]

It's not clear why the neighboring routers are not connecting directly. Inspecting the logs can provide more visibility on the issue.

Note that too strong a signal can be problematic for some radios due to receiver saturation issues.

[jiemincao]

Hi Jwhui :
Thank you for your reply.
I'm not sure what happens during the networking process, but whenever this issue occurs, I have to restart the router to make it resend the link request to solve the problem.
Is there any other solution?

[jwhui]

Without additional visibility, it is difficult to diagnose the issue.

What git commit are you using? Can you provide logs?

[jiemincao]

I'm using commit version 971f05f on the main branch.
I'm trying to find the logs from when it happened, particularly to understand why the router was removed from the neighbor table. Considering that the network environment consists of 300 FTD nodes in the same office, it's not easy to keep track of everything.