15 seconds delay when ssh to the KVM

KVM
1

After upgrading to version 1.8.2, I noticed a consistent ~15-second delay every time I SSH into my KVM. This behavior did not exist prior to the upgrade.

After running several tests, the issue appears to be a classic DNS timeout scenario, which is common in isolated or air-gapped environments.

Even though I was connecting via IP address, the SSH server (Dropbear) was still attempting a reverse DNS lookup—trying to resolve the client IP into a hostname, likely for logging or security purposes. Since no DNS service is available in my case, this results in the delay.

I tried a few approaches to bypass this behavior (including modifying the Dropbear startup script), but none were effective.

As a workaround, I added a static entry to the KVM’s local hosts file:

echo "192.168.x.x my-client" >> /etc/hosts

After doing this, SSH access becomes immediate with no delay.

I’m not sure if there’s a more elegant solution, but sharing this here in case others run into the same issue.

4

I don't know what your environment is like, but in my tests, it didn't have any issues. So it's difficult for me to make any modifications.

5

Thank for checking.

My environment is quite simple - DNS is set on the KVM, but it is not really reachable because network firewall blocked all traffic from the KVM to the Internet.

To reproduce my setup, you probably can set DNS on the KVM with the IP that doesn't exist in the network at all. In that case, the whenever the KVM tries to query DNS, it will turn to be timeout.