nginx-agent connection issues

This is me troubleshooting connectivity to F5 Distributed Cloud (XC) NGINX One Agent from our internal NGINX+ instances.

NGINX-AGENT Config File

cat /etc/nginx-agent/nginx-agent.conf

NGINX-AGENT Status

sudo systemctl status nginx-agent

NGINX-AGENT Log File

Start of log

sudo head -n 50 /var/log/nginx-agent/agent.log

End of log

sudo tail -n 50 /var/log/nginx-agent/agent.log

ERROR logs

time=2026-04-09T14:19:11.240Z level=ERROR msg="Unable to update data plane health" error="command service client not connected yet" correlation_id=142e437b-341f-11f1-aeca-506b8d721489 server_type=command

time=2026-04-09T14:19:11.999Z level=ERROR msg="Failed to create connection" error="rpc error: code = Unavailable desc = connection error: desc = \"transport: authentication handshake failed: credentials: cannot check peer: missing selected ALPN property. If you upgraded from a grpc-go version earlier than 1.67, your TLS connections may have stopped working due to ALPN enforcement. For more details, see: https://github.com/grpc/grpc-go/issues/434\"" correlation_id=11334b61-341f-11f1-aeca-506b8d721489 server_type=command

POTENTIAL ISSUE

-- Connecting through a proxy or load balancer that strips or doesn't support ALPN

** reach out to SECURITY team and validate they don't have a setting to strip out ALPN or http2 at the proxy

Check version of grpc-go

sudo dnf info python3-grpcio

Not root, Subscription Management repositories not updated
nginx agent repo                                                                                                                                                                                                          17 kB/s |  12 kB     00:00
EPEL_9                                                                                                                                                                                                                    28 MB/s |  25 MB     00:00
infratools_ansible                                                                                                                                                                                                       320 kB/s | 155 kB     00:00
Red Hat Enterprise Linux 9 for x86_64 - AppStream (RPMs)                                                                                                                                                                  21 MB/s |  86 MB     00:04
Red Hat Enterprise Linux 9 for x86_64 - BaseOS (RPMs)                                                                                                                                                                     24 MB/s | 109 MB     00:04
Available Packages
Name         : python3-grpcio
Version      : 1.46.7
Release      : 10.el9
Architecture : x86_64
Size         : 2.0 M
Source       : grpc-1.46.7-10.el9.src.rpm
Repository   : ALLYBANK_EPEL_9_epel_9_repo
Summary      : Python language bindings for gRPC
URL          : https://www.grpc.io
License      : Apache-2.0 AND BSD-2-Clause AND BSD-3-Clause AND MIT
Description  : Python language bindings for gRPC (HTTP/2-based RPC framework).

TEMP Workaround to test

Set Variable: GRPC_ENFORCE_ALPN_ENABLED=false on the client side

Rollback: unset  GRPC_ENFORCE_ALPN_ENABLED

ADD Additional DEBUG

GRPC_GO_LOG_VERBOSITY_LEVEL=99

GRPC_GO_LOG_SEVERITY_LEVEL=info

 Rollback

unset GRPC_GO_LOG_VERBOSITY_LEVEL=99

unset GRPC_GO_LOG_SEVERITY_LEVEL=info

NGINX-AGENT Restart

sudo systemctl restart nginx-agent

GET TCPDUMP of ALPN http2

sudo tcpdump -i any -nn -vv -s0 port 443 -A -w /home/user/nginx-agent-alpn-http2-20260415_1014.pcap

..