Upfgtp interface IPv4 address Allocation

Hello all,

I installed free5gc in Ubuntu 20.04 and Ubuntu 18.04+kernel 5.0.0-23-generic, but I noticed that the upfgtp interface only got allocated an IPv6 address without an IPv4 address in both environments.

Therefore, my UE of UERANSIM could not ping the external Internet via UPF using GTP/ICMP.
The PDU session was successfully established, and the the UE had an IP(60.60.0.1) in the GTP tunnel.

I also tried to install the latest version of gtp5g from GitHub - PrinzOwO/gtp5g: Linux kernel module 5G GTP-U, but it didn’t work, too.

Does anyone have ideas about this issue?

Hi @Jason

The upfgtp on my U-Plane VM is also as follows.

# ip addr show
...
4: upfgtp: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/none 
    inet6 fe80::9b7:6619:eb23:23f5/64 scope link stable-privacy 
       valid_lft forever preferred_lft forever

Tcpdumping upfgtp on the U-Plane confirms that ICMP packets are passing through this interface.

I think that the network needs to be set according to each environment.
Is NAT / NAPT of your U-Plane set properly?

1 Like

What was the configuration you used to support IPv4?

Was the update in the upfcfg.yaml? Did you make changes to the upf_config.c or upf_context.c?

Hello @s5uishida,

Thank you for the IP address info of upfgtp.
I thought my gtp5g module had a problem, but it was about network address configurations in free5gc and UERANSIM.

What network configuration did you do to fix your problem?

I am having the same issue with only having a IPv6 address, but for what I am doing I need an IPv4 address because of the ue or radio only supporting IPv4 (we can’t confirm this yet, but it is the theory).

Hi, Jason what changes you make in the upf config file to resolve the issue. Can you please let me know?