@Tom-Elliott apologies for the delay but here is what I see in the error log when this occurs:

For context the 'Client IP Detected as <IP ADDRESS> is a small modification to the Subnet Groups plugin which I log the IP of the client checking in, this is working as intended.

The ‘PHP Fatal error’ is what I only see when we have the chain loading error.

I can confirm this is working on: 1.5.10.1734 as I have rolled back any sites to this version and have seen no issues.

[Mon Feb 23 15:07:55.208763 2026] [proxy_fcgi:error] [pid 501804] [client 10.9.209.159:33595] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:08:27.815241 2026] [proxy_fcgi:error] [pid 501806] [client 10.9.209.159:1025] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:09:00.456158 2026] [proxy_fcgi:error] [pid 501802] [client 10.9.209.159:1555] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:09:33.088040 2026] [proxy_fcgi:error] [pid 501802] [client 10.9.209.159:6935] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:10:05.672334 2026] [proxy_fcgi:error] [pid 501803] [client 10.9.209.159:16900] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:10:38.336356 2026] [proxy_fcgi:error] [pid 571479] [client 10.9.209.159:43335] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496' [Mon Feb 23 15:11:10.976801 2026] [proxy_fcgi:error] [pid 501803] [client 10.9.209.159:36391] AH01071: Got error 'PHP message: SubnetGroup Hook: Client IP Detected as 10.9.209.159; PHP message: PHP Fatal error: Uncaught ValueError: min(): Argument #1 ($value) must contain at least one element in /var/www/fog/lib/fog/image.class.php:496\nStack trace:\n#0 /var/www/fog/lib/fog/image.class.php(496): min()\n#1 /var/www/fog/lib/fog/image.class.php(389): Image->getPrimaryGroup()\n#2 /var/www/fog/lib/fog/bootmenu.class.php(1472): Image->getStorageGroup()\n#3 /var/www/fog/lib/fog/bootmenu.class.php(469): BootMenu->getTasking()\n#4 /var/www/fog/service/ipxe/boot.php(52): BootMenu->__construct()\n#5 {main}\n thrown in /var/www/fog/lib/fog/image.class.php on line 496'```

@george1421 noted. When I was initially testing, I did not know this and it took some digging in the forums to find this tidbit of knowledge. Given that having separate storage groups stops replication between the nodes in my mind it makes most sense to have a more distributed setup of normal servers at each site to handle all of my requirements. Thanks for the input!

I reverted back to a snapshot I had on the same version and it’s working as expected. Unsure how things got corrupted but I would say it’s safe to assume this is working unless others report the same issue.

@Tom-Elliott latest pull resolved the issue. Appreciate your help on this!

@Tom-Elliott, disregard this request.

I edited ‘addsubnetgroup.hook.php’ which simplified getting the client IP and adding the host to the respective group. I understand this also removes certain checks that were in place but for my environment it is now working as intended.

Old ‘addSubnetgroupHost’ function:

public function addSubnetgroupHost($arguments) { if (!in_array($this->node, (array)self::$pluginsinstalled)) { return; } $Host = $arguments['Host']; $mac = $Host->get('mac'); if (!isset($mac)) { return; } // Setup for tests $name = $ipn = $Host->get('name'); $ip = $Host->get('ip'); $ipr = self::resolveHostname($name); // Perform all tests. $ip1t = filter_var($ip, FILTER_VALIDATE_IP); $ip2t = filter_var($ipn, FILTER_VALIDATE_IP); $ip3t = filter_var($ipr, FILTER_VALIDATE_IP); // If resolve hostname returns a valid IP, set IP appropriately. // Otherwise, if the name is valid, use it. // Otherwise, return if base $ip is false. if (false !== $ip3t) { $ip = $ipr; } elseif (false !== $ip2t) { $ip = $ipn; } elseif (false === $ip1t) { return; } // Now list our subnet groups. Route::listem('subnetgroup'); $SNGroups = json_decode(Route::getData()); foreach ($SNGroups->subnetgroups as &$SNGroup) { if (in_array($SNGroup->groupID, $Host->get('groups'))) { $Host->removeGroup($SNGroup->groupID)->save(); } $subnetList = str_replace(' ', '', $SNGroup->subnets); $subnets = explode(',', $subnetList); foreach ($subnets as &$subnet) { if ($this->_ipCIDRCheck($ip, $subnet)) { $Host->addGroup($SNGroup->groupID)->save(); unset($subnet); continue 2; } unset($subnet); } unset($SNGroup); } }

New code:

public function addSubnetgroupHost($arguments) { if (!in_array($this->node, (array)self::$pluginsinstalled)) { return; } $Host = $arguments['Host']; $mac = $Host->get('mac'); if (!isset($mac)) { return; } // Use the real source IP from the request $ip = $_SERVER['REMOTE_ADDR']; // Now list our subnet groups. Route::listem('subnetgroup'); $SNGroups = json_decode(Route::getData()); foreach ($SNGroups->subnetgroups as &$SNGroup) { if (in_array($SNGroup->groupID, $Host->get('groups'))) { $Host->removeGroup($SNGroup->groupID)->save(); } $subnetList = str_replace(' ', '', $SNGroup->subnets); $subnets = explode(',', $subnetList); foreach ($subnets as &$subnet) { if ($this->_ipCIDRCheck($ip, $subnet)) { $Host->addGroup($SNGroup->groupID)->save(); unset($subnet); continue 2; } unset($subnet); } unset($SNGroup); } }

My RP address was not pointing to my FOG server 🤦

Once this was adjusted, multicast is functional. Definitely a good reminder to start small.

I found the issue!

The udpsender path on my system was “/usr/sbin/udp-sender”

The path that is set within config.class.php is:

define('UDPSENDERPATH', '/usr/local/sbin/udp-sender');

I ran the following and restarted the FOGMulticastManager to resolve:

sudo ln -s /usr/sbin/udp-sender /usr/local/sbin/udp-sender

And we have logs now! Time to begin multicast testing 🥳