Building Automation Knowledge Base

Issue Troubleshooting Sigma IC LON Values going on and offline Product Line Satchwell Sigma Environment Sigma Release 4_05-SEB (Build 3_43_18) Sigma Release 4_05-SP2 (Build 3_42_48) Sigma Release 4_06 (Build 3_44_14) Sigma Release 4_06 SP1 (Build 3_44_16) Sigma Release 4_07 (Build 3_45_48) Sigma Release 4_07-SP1 (Build 3_45_51) Sigma Release 4_07-SP2 (Build 3_45_58) Sigma Release 4_08 (Build 3_46_57) IC LON Cause Lon Values going into and out of default Resolution Compare the IC-LON’s Receive heartbeat set in the “gateway.txt” file in the IC-LON controller, to the send heartbeat set in the controller. The recommendation is for the receive heartbeat be set to 2-5 times the send heartbeat of the field controller. Starting at 2 times, then increasing if the problem persists. If the controller doesn’t have a heartbeat and the LON value rarely changes, disable the receiver heartbeat in the IC-LON’s gateway.txt file by setting the heartbeat to 0. Example: 1     2     3        4      5   6  7 2,   2,  112,  1293,  0,  0, 0   The Sigma system is now out of its support period, consideration should be given to transitioning or upgrading to SpaceLogic - EcoStruxure Building Operation.

Issue Need to send Continuum alarm messages to email addresses  Product Line Andover Continuum Environment Continuum Cyberstation Cause Alarm delivery required to remote users via email.  Resolution Please note this resolution is applicable to all versions of Continuum Cyberstattion and requires Microsoft Exchange or Outlook to send emails.  However, CyberStation version 2.xx does not necessarily require Microsoft Exchange or Outlook to send emails for alarm notifications. Instead, it is possible to configure an SMTP server on the network and use it to send alarm email notifications directly to the intended recipient.  Please refer to SMTP Email Alarm Configuration in Continuum 2.00 to 2.03    Here are some requirements for forwarding Continuum workstation alarm events via email and paging: The Continuum workstations that have been designated primary and backup email and/or page handlers must have an email client such as Microsoft Exchange or Outlook. The email client application must communicate with an existing email server application, such as MS Exchange Server. The primary or backup email/paging workstation must be running Continuum at the time an alarm is generated. Each EventNotification object associated with the alarms that you wish to email or page must have its own email distribution list in the personal address book of the client email application using a specified naming convention as outlined in the table below. This email distribution list must be stored in the first address book shown in the list of available address books in the email client application. For example, if you create an EventNotification distribution list in the Personal Address Book in Microsoft Outlook, then the Personal Address Book must be the first one showing in the address list dropdown box when you open the Address Book.   How to Create an EventNotification Distribution List Note: The following steps are based on Microsoft Outlook. Other mail applications may have different menu names and choices but the general procedure is the same. Step Action 1 Open the Address Book for the email account on the Continuum workstation that will be providing the email/paging services. Your toolbar may have a button for this. If not, use the Address Book option of the Tools menu. 2 Select New Entry from the Address Book File menu. 3 Select the entry type Personal Distribution List and put this entry in the Personal Address Book. 4 In the Name field enter a name for the distribution list using the following format: For E-mail: ACC.name For Paging: ACC.page.name where name is the name of the EventNotification. 5 Add members (the email addresses or pager and service numbers of those to whom the notification of the alarm will be sent) to your personal distribution lists. 6 Set address book options so that the address book where your personal distribution lists are stored is the first one to be searched when sending emails or pages.

Issue What is the password recovery procedure for the SpaceLogic Operator Display if the password is lost? Product Line EcoStruxure Building Operation Environment SpaceLogic Operator Display Cause If losing the password for the SpaceLogic Operator Display there is no password recovery procedure available to recover it. The only option to access the device again is to do a device recovery procedure on the device. When doing a device recovery on the device everything on it, all users, configuration data, and logs will be deleted and a new firmware loaded into the device Resolution Steps to perform a device recovery procedure:   Download the device recovery file (tar.gz file) which is included in the “SpaceLogic Operator Display HMIST6400SL Firmware Package” which you can download from Schneider Electric Exchange Extract files and copy them to a USB stick (Format: FAT) a. Unpack the tar.gz  b. Two unpacks are required, then "aurora" folder should be present c. Copy whole "aurora" folder to a USB stick d. The structure on disk should be: e. aurora (folder)-FIRMWARE (folder)- AURORA.CFG-nand.img Power off OPD (Operator Display) Connect a USB-OTG cable (On-The-Go cable, USB-micro-B to USB-A) to the USB-2 port on the rear of OPD . Note: The cable is like a key, to enable device recovery. Do NOT connect USB stick to cable. Connect the USB stick to the USB-1 port on the rear of the OPD Power on OPD Device will boot to a white screen and display: Recovery Mode Loading nand.img... Writing KERNEL... Writing ROOTFS... Udisk upgrade success! (Loud beep) "Upgrade successfully, Wait to Reboot!" Power off OPD. Remove USB stick and USB-OTG cable Power on device and it will boot to the loaded firmware Firmware version is shown on startup screen.   For more details see video:  

Issue What is the Intel Floating point number as used in the Modbus X Driver? Product Line Andover Continuum Environment Modbus RTU X Driver Cause It is not clear how the two special floating point function codes vary. Resolution There are two different floating point data formats (248 & 245) these are both standard 32 bit floating point numbers but the data bits stored in memory (or read over the protocol) differently.   The 32 bits of Function 248 are stored as one string of bits, bit 0 through to bit 31.   For the 245 format the upper and lower words are swapped around, so it stores the data as bits 15 to 0, then bits 31 to bit 16. This format is called Intel format as it is the way Intel microprocessors handle floating point data.   Here is a link to information on floating point numbers FYI: https://en.wikipedia.org/wiki/Floating-point_arithmetic   These two formats can also be called Big Endian (Function 248), or Little Endian (Function 245). Little Endian is also known as the Intel format. Information on Endianness can be found at: https://en.wikipedia.org/wiki/Endianness

Issue How are the 'Advanced Polling Configuration' settings under the BACnet interface to be used? Product Line EcoStruxure Building Operation Environment Enterprise Server (ES) Automation Server (AS) Cause These settings can be used to reduce traffic on the BACnet networks that can overload both the EBO server as well as the devices being polled. Resolution The settings are used to specify an amount of time (in milliseconds) that the server should wait after completing a polling cycle on the applicable BACnet network before starting the next cycle. A polling cycle is the set of point being polled on a particular network interface. For example, lets assume that the Minimum polling interval for MSTPA network has been set to 1000 ms, if you are polling 30 points on MSTP port A then the BACnet plug in will do synchronous ReadProperty requests to poll each of the 30 points one at a time. Once the 30 points are polled, (one polling cycle) the BACnet plug-in will delay 1000ms before polling the 30 points again. (next polling cycle) NOTE: The settings apply to polling ONLY and do not affect communications done via change of value (COV) To find a proper value to use, it is recommended that you start with 1000 ms and then adjust the value up or down based on polling performance. If the polled values update fast enough, increase the minimum polling interval to reduce CPU usage. If the polled values become too sluggish, reduce the minimum polling interval until performance returns to satisfactory levels. It may take some trial and error to find the optimum balance.

Issue Understanding Access Expert's schedules holidays and one-offs and their interaction with Triggers and Procedures Product Line EcoStruxure Access Expert Environment Access Server Hosted Software Access Server Premise Software Cause More details on schedules holidays and one-offs are needed to clear confusion about Triggers & Procedures configuration. Resolution Let's first break this down into some basic principles on Schedules and Holidays.   Schedules can become active or inactive. A status change is commonly used as a Trigger to some procedure (ie change a reader mode to unlocked) Holidays act as schedule masks so that schedules cannot become active or inactive, thus never triggering. With that in mind; One-off dates are SCHEDULE behaviors, similar to how choosing "Monday" is a scheduled behavior. All schedules can be masked by holiday configurations. Special dates are HOLIDAY behaviors. They act as flags that effectively invert the bit that would normally mask, performing the inverse behavior. Now that we've established those event types and configurations, let's go over Triggers & Procedures. As mentioned in (1) that a status change is a trigger because it is a generated Mercury event. These triggers do whatever procedure you instruct them to do. As a result, whenever a trigger occurs that activates procedures A or B, or C, those procedures will execute.   When configuring many reader modes you can quickly and easily produce conflicts where a schedule becomes active and thus a procedure occurs, which sets a behavior that another schedule does not like because that trigger already happened. There is no concept of "following a schedule" in Mercury. In order to correctly configure reader modes, you will want to limit the normal modes to as few as possible (preferably 1) and instead create intelligent sets of schedule INTERVALS within one schedule, more specifically, you wouldn't use multiple modes, you would use 1 mode with a schedule containing multiple intervals.   If you would like a schedule to ignore a holiday, you would set "ALWAYS ACTIVE ON" and choose your holidays in the interval(s). The trick here is not to apply holidays to schedules that are not normally active.   Mercury controllers support up to 8128 Triggers and 8128 Procedures. Holidays Mask schedules from becoming active. Always Active On will ensure that a schedule is NOT MASKED for that holiday group, by flipping a bit.   For customers using many sites which their own holiday restrictions, we offer enterprise licensing. Each location should have its own shared instance where holidays are localized to that instance's controllers and hardware. Holidays should only be implemented when you want to mask schedules, if you then have schedules that shouldn't be masked, you would apply the "always active on" for those groups. If you have a schedule that won't become active on that holiday, then there's no need to override using always active on.

Issue Internal counter stops counting. Product Line EcoStruxure Building Operation Environment Script Function Block Counter 167777216 Cause When this script is used it stops counting at 16777216. Numeric Output CountOut   Main: CountOut = 16777100 goto Counter Counter: CountOut = CountOut + 1   Resolution This issue was identified in the early days of Continuum and is regarded as a limitation, not a defect. Explanation - Internally the Script handles all numbers as IEEE754 single precision floats, which means that 16777216 is handled as 1.6777216E7. Adding 1 to 16777216 is unrecognizable in that representation. Using an IEEE754 converter at https://www.h-schmidt.net/FloatConverter/IEEE754.html, one can see that 16777216 and 16777217 have the same binary representation. The point at which the counter will stop, will depend upon the value being added each time, so adding 0.9 will count to a different number than adding 1. The counting range can be extended by two or more variables as shown below. Numeric Output CountOut Numeric CountOut1 Numeric CountOut2   Main: CountOut1 = 16777100 goto Counter1   Counter1: CountOut1 = CountOut1 + 1 CountOut = CountOut1 if CountOut1 = 16777216 then goto Counter2   Counter2: CountOut2 = CountOut2 + 1 CountOut = CountOut1 + CountOut2  

Warning Potential for Data Loss: The steps detailed in the resolution of this article may result in a loss of critical data if not performed properly. Before beginning these steps, make sure all important data is backed up in the event of data loss. If you are unsure or unfamiliar with any complex steps detailed in this article, please contact Product Support Services for assistance. Issue User of EcoStruxure Building Operation WorkStation used the "Remember me on this computer" option and logged into an account that does not have account rights to logout. Product Line EcoStruxure Building Operation Environment WorkStation Cause A situation such as this could happen either due to inattention of the user or because of planned system design (Kiosk with Building Operation WorkStation logged into a read only account). However it might be necessary due to maintenance to adjust the login option. In the absence of a kiosk situation, it is recommended to always leave the ability for a user to logout by only hiding the toolbar instead of disabling it. Resolution The solution can differ depending on the installation or usage scenario. User has access to log off option Once logged into Building Operation WorkStation use the log off option to return to the login prompt Uncheck the "Remember me on this computer" option. Enterprise Server on another computer or accessing an Automation Server Disconnect the Ethernet cable for the computer or disable the network port Building Operation WorkStation attempts to login returning user to the login prompt. Enterprise Server on same computer The Enterprise Server can be stopped temporarily and the next attempt to start Building Operation WorkStation will result in a communication failure allowing you to modify the "Remember me on this computer" selection. This could result in loss of data while the Enterprise Server is stopped. Delete the Building Operation WorkStation configuration file (named either SBO.ClientUserProfile.bin or TAC.ClientUserProfile.bin for older versions) stored in the computer application data. Deletion of this file will result in loss of custom settings such as column widths and similar customizations.

Warning Potential for Data Loss: The steps detailed in the resolution of this article may result in a loss of critical data if not performed properly. Before beginning these steps, make sure all important data is backed up in the event of data loss. If you are unsure or unfamiliar with any complex steps detailed in this article, please contact Product Support Services for assistance. Issue After successfully setting up KIOSK mode to automatically login in to WebStation another user wants to login through WebStation on the same PC. Product Line EcoStruxure Building Operation Environment EcoStruxure Building Operation WebStation Cause The GUEST account login URL used with KIOSK mode retains the last user logged in and the WebStation menu bars have been removed so that user cannot "logout". Any subsequent attempts to access the WebStation using the same browser result in being automatically logged in under the GUEST account. Resolution The "KIOSK" link that you create will login automatically with the GUEST account as long as the GUEST account has already been created in the ES/AS. This then must set the "last credentials" in IE for that website and any subsequent connections to that server, even to the direct login URL, result in automatically being logged in with those last credentials. One of the two options below should work to disable GUEST login depending on where your ES is located. Enterprise Server on another computer or accessing an Automation Server Disconnect the Ethernet cable for the computer or disable the network port while Building Operation Workstation attempts to login returning user to the login prompt. Enterprise Server on same computer The Enterprise Server can be stopped temporarily and the next attempt to start Building Operation Workstation will result in a communication failure allowing you to modify the "Remember me on this computer" selection. To be prompted for a login: Disconnect the ES/AS with one of the options above. Then try to connect to the server page at "http:/localhost:444" (or your specific URL:Port). This results in a "this page can't be displayed" (or similar) message. Then start the service, or reconnect cable, and again attempt to connect to "http:/localhost:444". You should be presented with the login page. Do not try to open up the "KIOSK" URL or else this will again login with the GUEST account and you'll be back to square one. The next time you use the "KIOSK" URL it will automatically login with the GUEST account and this will again be used for subsequent logins until the above steps are repeated. Note1: This could result in loss of data while the Enterprise Server is stopped. Note2: Also see StruxureWare Building Operation Workstation Auto Login feature locked if encountering this issue with a Workstation.

Issue Unable to see EWS objects/points under an EcoStruxure Web Services interface Product Line EcoStruxure Building Operation Environment EcoStruxure Web Services (EWS) Enterprise Server Automation Server Cause An EWS License may be needed to allow your ES/AS to use EcoStruxure Web Services Resolution Purchase and install an EWS License if required.     Note: The EWS option is NOT required when using EWS to integrate between two Schneider Electric systems or services. Refer to PA-00349 for details.   This includes the new Smart Connector by Schneider Electric which does not require an EWS License but does require a Smart Connector License as usual

Issue How to transfer EBO 2022 or higher data to Azure IoT hub via MQTT protocol Product Line EcoStruxure Building Operation Environment Building Operation Enterprise Server Building Operation Automation Server Premium Building Operation Automation Server Bundled Cause Need to configure EBO MQTT interface and Azure IoT Hub, so EBO can send MQTT messages to Azure MQTT IOT Hub. Resolution The following video will illustrate how to: Create Azure IoT hub and IoT device using Azure Portal Create IoT interface and Azure MQTT client in EBO Configure the MQTT connection Create and configure a data group Test the connection Things you need: EBO 2022 or later with valid MQTT license or demo license (Enterprise Server, AS-P or AS-B) valid Azure Subscription with possibility to use free account during testing. For each Azure subscription one IoT hub in the free tier can be created, refer to IoT Hub | Microsoft Azure Visual studio code to be used to test the connection between EBO and Azure IoT hub, can be download from: Visual Studio Code

Issue Automation / Enterprise Server configuration very slow Attempting to make any configuration changes in the AS such as creating a new point/value or modifying existing objects is extremely slow. Note: This applies to the ES as well although less of a problem since the ES has better resources than the AS. CPU usage as seen in the Status Information of the server is very high. (above 80%) Question marks are shown on many objects in the application folder of third party BACnet devices that have been uploaded to the AS Enterprise Server takes a long time to startup (15 minutes) before allowing users to log on with Workstation.  Deleting the BACnet Interface allows log on with 2 - 3 minutes on a restart. Product Line EcoStruxure Building Operation Environment Automation Server Enterprise Server BACnet Cause Uploaded BACnet devices contain unresolved references to notification class object(s) Resolution Ask for SE.SBO.ES-AS-1.5.0.1501-Hotfix. (SE.SBO.WS-1.4.1.16001-Hotfix for 1.4.1, there is no hot fix for versions before 1.4.1) After applying the hot fix the server should become responsive. The unresolved references can typically be cleaned up by creating a BACnet Notification object in the application folder of the third party BACnet device proxy that reside in SBO and manually setting the Instance ID to 0 (zero) NOTE: Cases have been seen where multiple notification class objects must be created using instance IDs 0,1,2,3,4 in order to clean up all the unresolved references. A few minutes after the notification class object with the proper instance ID is created the question marks should disappear from the icons and created notification class object will show up in the intrinsic alarm property as seen below.   If creating the notification class objects with the above instance IDs does not resolve all the references a backup of the server can be provided to PSS, a PSS/R&D engineer can look directly at the database to determine the proper instance IDs the unresolved references are looking for.

Warning Potential for Data Loss: The steps detailed in the resolution of this article may result in a loss of critical data if not performed properly. Before beginning these steps, make sure all important data is backed up in the event of data loss. If you are unsure or unfamiliar with any complex steps detailed in this article, please contact Product Support for assistance. Issue Locating and downloading latest images Product Line Satchwell Sigma Environment 3.46.57 3.46.66 3.46.80 3.46.89 3.46.100 3.46.104 3.46.105 3.46.106 3.46.107 3.46.108 3.46.110 3.46.111 3.46.131 Cause Identifying the correct image version for different hardware versions. Resolution Sigma UNC/ (V53) = Firmware 6b Sigma Firmware UNC596 6.b - Release note   Sigma UNC3 (ARM7) = firmware build 1.p.0 Sigma Firmware 1.p.0 UNC3 - Release note   UNC 532 V25 = Firmware 6b Sigma Firmware UNC532 6.b - Release Note   IC-Modbus = Firmware V5h IC-Modbus v5h Release Note   IC3 Modbus = Firmware1.n.2 IC3 Modbus - Release Note   IC SNP = Firmware 5d IC-SNP Integration Controller v5d for Sigma Rel 3 - Release Note   IC3 SNP = Firmware 1.g.1 Sigma 4.05 Firmware Supplement - Release Note (there is no release note specific to SNP Firmware 1g.1).   IC York = Firmware V3e - Not available to download. IC-York Integration Controller v3e for Sigma - Release Note   IC3 York = Firmware 1.d.0 IC3 York = Firmware 1.d.0 – Release Note   Sigma IC3 Unifact 1.d.0 – Firmware Sigma IC3 Unifact (RTC) - Release Note Sigma IC3 Unifact pro 5h – Firmware Sigma IC3 Unifact pro 5h - Release Note  

Issue After setting up a UNC as a BBMD the other UNC's on that subnet are getting "network mismatch" errors in their standard output windows. Product Line TAC IA Series Environment R2 UNC's with BACnet jar's earlier than 535a. Cause This type of error is indicative of a routing loop on the BACnet internetwork.  UNC's with a BACnet jar prior to 535a when set up as a BBMD will broadcast on their own subnet as well as to the other BBMD's and this can cause that also. Resolution Install BACnet jar 535a or later in the UNC that is the BBMD to see if this corrects this issue.  If the issue persists investigate the BACnet internetwork for a router loop. 

Issue How to configure a G3 station as a BACnet BBMD Product Line TAC IA Series Environment I/A Series G3 version 3.3.22 and later Cause Documentation Resolution In the G3 Station, expand the BacnetNetwork, expand Bacnet Comm, expand Network, and then double-click IP Port.  The IP Port Property Sheet opens (see below)   In the IP Device Type drop-down, select Bbmd.  Click Save The station is now configured as a BACnet BBMD

Issue On a large system with more than 32 subnets, is their a workaround for the 32 BBMD limit on a Continuum system? Product Line Andover Continuum Environment BBMD Foreign Device Registration. Subnets Cause It is not possible to configure more than 32 BBMDs within a BCX40xx. Resolution While foreign device registration can be used as a workaround when controllers must be installed on a subnet but no additional BBMDs can be configured, foreign devices present their own limitations. Let's say we have two subnets.  Subnet A has a BCX4040 that is configured as a BBMD.  On subnet B there are two BCX4040 controllers.  One controller on subnet B is registered as a Foreign device with the BBMD on subnet A Foreign Device Table registration supports up to 1024 devices on the workstation (v1.94 and later).

Issue How many BBMDs and Foreign Devices can be registered on a CyberStation and a bCX4040?   Product Line Andover Continuum Environment BACnet bCX4040 CyberStation BBMD Foreign Device  Cause Concerned about large BACnet sites and exceeding a limitation on the number of BBMDs and Foreign Devices that can be registered.  Resolution Maximum number of BBMDs The maximum number of BBMDs that can be registered on a bCX4040 or on a CyberStation is 32.   Maximum number of Foreign Devices (FDs) Continuum v1.93 or earlier The maximum number of Foreign Devices (FDs) that can be registered on a bCX4040 or on a CyberStation is 64. Continuum v1.94 or later The maximum number of Foreign Devices (FDs) that can be registered on a CyberStation is 1024 The maximum number of Foreign Devices (FDs) that can be registered on a bCX4040 is 64.

Issue Configuration of multiple BACnet BBMD's over several subnets Product Line Andover Continuum, EcoStruxure Building Operation Environment Bacnet BBMD Cause Bacnet Broadcast communication through IP router Resolution Configuration of multiple BBMD's over several subnets: INCORRECT METHOD For example if there are 4 subnets on the same B/IP (BACnet IP Network): Subnet 1: Workstation setup as a BBMD with an entry in the Broadcast Distribution Table for each BCX Subnet 2: BCX setup as a BBMD with an entry in the Broadcast Distribution Table for itself and the Workstations BBMD Only. Subnet 3: BCX setup as a BBMD with an entry in the Broadcast Distribution Table for itself and the Workstations BBMD Only. Subnet 4: BCX setup as a BBMD with an entry in the Broadcast Distribution Table for itself and the Workstations BBMD Only. The BCX's do not reference any points from each other. Since there is no data sharing between the BBMD's, one might think that in each BCX's Broadcast Distribution Table that there would only be a need to add one entry for the Workstations BBMD. Sounds like with this setup we'll reduce traffic by only adding the one entry in each BCX's BBMD Broadcast Distribution Table. The above scenario could in fact slow down a network and cause unnecessary traffic.   The supported method is that every BBMD on a B/IP network have the same routing tables(better known as the Broadcast Distribution Table) as in the below configuration. CORRECT METHOD For example there are 4 subnets on the same B/IP (BACnet IP Network). Subnet 1: WS BBMD with an entry in the Broadcast Distribution Table for itself and all BCX's setup as BBMD on the same B/IP. Subnet 2: BBMD with an entry for all BBMD's(including self) in the Broadcast Distribution Table on the same B/IP. Subnet 3: BBMD with an entry for all BBMD's(including self) in the Broadcast Distribution Table on the same B/IP. Subnet 4: BBMD with an entry for all BBMD's(including self) in the Broadcast Distribution Table on the same B/IP. The entry below can be found in the BACnet Standards 2004:   J.4.3 BBMD Concept Each IP subnet that is part of a B/IP network comprised of two or more subnets shall have one, and only one, BBMD. Each BBMD shall possess a table called a Broadcast Distribution Table (BDT) which shall be the same in every BBMD in a given B/IP network.

Issue Cannot open Calendars on several BACnet Networks. Product Line Andover Continuum Environment Continuum 1.9X BCX 4040 B38XX controllers Cause BBMD Sub Net Mask Configuration. Resolution There are two configuration methods allowed in a BBMD Subnet mask. One hop configuration and a Two hop configuration. See Understanding BACnet BBMD Distribution Mask for further details

Issue When configuring a BBMD what is the Broadcast Distribution Mask and what are the valid settings for the field. Continuum EcoStruxure Building Operation Product Line EcoStruxure Building Operation, Continuum Environment Building Operation Automation Server Building Operation Enterprise Server Continuum CyberStation bCX4xxx Cause Documentation Resolution When configuring a BBMD the BACnet protocol defines two methods of propagating the broadcasts messages to other networks. The two methods are referred to as One-Hop also known as a Directed Broadcast and Two-Hop.   Note: In this article the subnet mask is shown using Classless Inter-Domain Routing(CIDR) notation. An IPV4 address is 32 bits long, CIDR notation defines the number of bits used for the subnet mask. The most commonly used are: /8 or 255.0.0.0 /16 or 255.255.0.0 /24 or 255.255.255.0 /32 or 255.255.255.255 One-Hop With the One-Hop method the local BBMD transfers the message directly to the remote devices via the remote router. In this case the IP routers have to support the transfer of IP broadcast messages to remote IP subnets Figure 1 Figure 1 above illustrates the one-hop method, when the bCX1 which has been configured to take the role of BBMD for network 172.16.0.0/16 detects broadcast messages such as WHO-IS, I-AM etc, it sends a message directly to the broadcast address of the 192.168.1.0/24 subnet, it is then up to Router2 to send the directed broadcast to all devices on the subnet. Any device on the subnet that is acting as a router to other networks will then also re-broadcast the message on those networks. (i.e a bCX hosting an MSTP network on COMM2)   Two-Hop With the Two-Hop procedure a BBMD device transfers broadcast messages to a further BBMD in the remote IP subnet, which then distributes the messages in its local network as IP broadcast messages for its IP subnet. Any device on the subnet that is acting as a router to other networks will then also re-broadcast the message on those networks.(i.e a bCX hosting an MSTP network on COMM2) Figure 2 Figure 2  above illustrates the two-hop method, when the bCX1 which has been configured to take the role of BBMD for network 172.16.0.0/16 detects broadcast messages such as WHO-IS, I-AM etc, it sends a unicast message to each BBMD device on its table, it is then up to each BBMD device on each subnet to send a broadcast that will be heard by all devices on the subnet. Which distribution mask should be used? As mentioned earlier, in order for the one-hop method to work, the router on the remote subnet MUST be configured to process incoming messages sent to the broadcast IP address, the two-hop method on the other hand is guaranteed to work, so when in doubt use the two-hop method. Most sites use two-hop distribution for the reason stated above,, the only obvious disadvantage of the two-hop method is that it is a little more verbose than the one-hop method since the message appears twice on the subnet, once as a unicast sent to the BBMD device and then again as a broadcast sent by the BBMD device. In Building Operation and Continuum the distribution mask defaults to the two-hop method (/32 or 255.255.255.255) How to configure the distribution mask For one-hop enter the subnet mask of the remote network in the distribution mask, the system will apply the mask to the IP address to obtain the broadcast address for the remote network. For two-hop enter 255.255.255.255, this tells the system not to do a direct broadcast and instead do a unicast to the remote BBMD device. Sample distribution mask In the BBMD table of a bCX shown in the screen shot above, BDT #1 and #3 use the two-hop method while BDT entry #2 uses the one-hop method.