Nodes in a symmetric network cannot get data

During my testing of Kubo, I discovered an issue: when I start a Kubo peer in a symmetric network, it fails to retrieve any data. However, it works fine in a CONE-based LAN. I carefully examined the relevant source code and discovered that Hole Punching does not support symmetric networks; hole punching will not succeed in symmetric networks and CONE.

if a Kubo peer with Relay v2 enabled has never received data, Kubo peers in a symmetric network will never be able to retrieve the desired data. How can I resolve this issue?

This is my test scenario: