[Bug]: NAT modifies TTL incorrectly

[Chaoping]

Version

7.2.4

Host OS Type

Windows

Host OS name + version

Windows 11 Build 26200.7462

Host Architecture

x86

Guest OS Type

Linux

Guest Architecture

x86

Guest OS name + version

Lubuntu 22.04 LTS

Component

Network

What happened?

In guest system, when runing ping command to any server on the internet, TTL always reports 255. Using Wireshark inside the VM to capture ICMP echo reply, TTL is indeed 0xFF.

For outgoing packets, TTL is also modified at the NAT. This can be seen by running traceroute -I command to any server from the guest system. The result is always single line, as if the target server were in the local area network. Likely the NAT changed TTL from 1 to some large number.

A forum post in 2024 also reported this issue: https://forums.virtualbox.org/viewtopic.php?p=551779

By uninstalling VirtualBox 7.2.4 and installing an older version (I tried 7.0.8), the problem is gone.

How can we reproduce this?

Run Lubuntu 22.04 guest in VirtualBox 7.2.4 Windows 11 host, and run ping, traceroute commands, and see the packets in Wireshark. It's always like that.

Did you upload all of your necessary log files, screenshots, etc.?

• Yes, I've uploaded all pertinent files to this issue.

[thatnerdjack]

Hi @Chaoping! Could you let me know if this is an issue on NAT or NAT Network? I'd also really like to see a VBox.log file per the issue reporting instructions. Thanks!