UMC of the Primary Directory Node (5.0.9) Accessible Only via IP, Not FQDN

Hi @all,

I’m facing an issue where I can only access the UMC of my Primary Directory Node via its IP address, but not through its hostname. DNS resolution is working fine I can log into the server from the client using:

ssh -l root srv01.lan.example.de

A DNS diagnostic from the client returns:

sven ツ lt001:~ dig srv01.lan.example.de

; <<>> DiG 9.18.30-0ubuntu0.22.04.2-Ubuntu <<>> srv01.lan.example.de
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19547
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 3

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;srv01.lan.example.de.		IN	A

;; ANSWER SECTION:
srv01.lan.example.de.	276	IN	A	192.168.83.5

;; AUTHORITY SECTION:
lan.example.de.		276	IN	NS	srv01.lan.example.de.
lan.example.de.		276	IN	NS	gw02.lan.example.de.

;; ADDITIONAL SECTION:
gw02.lan.example.de.	276	IN	A	192.168.83.20
srv01.lan.example.de.	276	IN	AAAA	2a02:wwww:xxxx:yyyy:zzzz:ebff:fe28:35be

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53) (UDP)
;; WHEN: Wed Feb 05 19:29:59 CET 2025
;; MSG SIZE  rcvd: 141

This problem does not occur with the other UCS servers (Replica Directory Node or Managed Node, all running 5.0.9). It might be relevant to mention that this is a dual-stack setup (IPv4 & IPv6). The IP configuration of srv01 is:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc mq state UP group default qlen 1000
    link/ether 5a:65:eb:28:35:be brd ff:ff:ff:ff:ff:ff
    inet 192.168.83.5/24 brd 192.168.83.255 scope global ens18
       valid_lft forever preferred_lft forever
    inet6 2a02:wwww:xxxx:yyyy:zzzz:ebff:fe28:35be/64 scope global dynamic mngtmpaddr 
       valid_lft 86362sec preferred_lft 14362sec
    inet6 fe80::5865:ebff:fe28:35be/64 scope link 
       valid_lft forever preferred_lft forever

The client’s IP configuration (Linux Mint 21.3) is:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: wlp0s20f3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether dc:8b:28:15:ed:89 brd ff:ff:ff:ff:ff:ff
    inet 192.168.83.141/24 brd 192.168.83.255 scope global dynamic noprefixroute wlp0s20f3
       valid_lft 31337sec preferred_lft 31337sec
    inet6 2a02:wwww:xxxx:yyyy:zzzz:342a:7153:d96b/64 scope global temporary dynamic 
       valid_lft 85934sec preferred_lft 13934sec
    inet6 2a02:8071:7102:a1dc:5856:7f22:88dc:e873/64 scope global dynamic mngtmpaddr noprefixroute 
       valid_lft 85934sec preferred_lft 13934sec
    inet6 fe80::aa0f:25ea:79b9:43a2/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

When attempting to access the UMC in the web browser (Firefox), I receive the following error:
“Forbidden: You don’t have permission to access this resource.”

In the Apache log file on srv01, I find this:

==> error.log <==
[Wed Feb 05 19:41:33.153497 2025] [access_compat:error] [pid 4151] [client 2a02:wwww:xxxx:yyyy:zzzz:342a:7153:d96b:48158] AH01797: client denied by server configuration: /var/www/univention/portal/

==> access.log <==
2a02:wwww:xxxx:yyyy:zzzz:342a:7153:d96b - - [05/Feb/2025:19:41:33 +0100] "GET /univention/portal/ HTTP/1.1" 403 1576 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:134.0) Gecko/20100101 Firefox/134.0"
2a02:8071:7102:a1dc:9850:342a:7153:d96b - - [05/Feb/2025:19:41:33 +0100] "GET /favicon.ico HTTP/1.1" 200 1476 "https://srv01.lan.example.de/univention/portal/" "Mozilla/5.0 (X11; Linux x86_64; rv:134.0) Gecko/20100101 Firefox/134.0"

What could be causing this issue?

with best
sven

This behavior occurs exclusively on the Directory Manager Node as soon as IPv6 is activated using SLAC. If IPv6 is switched off, it works. It works without any problems on the other roles (Replica Directory Node, Managed Node).