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  1. #1
    Join Date
    Jan 2019
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    3
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    How to get BBMD's through an IP Router

    Hello, I have been in the controls world for a long time. I have installed and serviced many systems. Recently, I decided to do some testing on setup up a little IP network with two subnets and communicating across the subnets using BBMD's. I have setup many systems with BBMD's in commercial buildings with real professional IT guys. I have never had a problem setting up the systems as everything always communicated fine.

    Well I am finding out that the IT guys must be setting up some special routing in the IP routers that I am unaware of. I am using cheap little (and this is probably my problem) domestic IP routers. I can't get the BBMD's to pass through the IP routers.

    I have two IP routers with subnets of 192.168.11.0/24 and 192.1.10.0/24. I can't ping the devices from one network to the other. I have set up all the routing tables in the cheap little routers (and have edited them a gazillion times trying to get it to work) I can't get the information to pass. I replaced the firmware with tomato on one IP router hoping I could get it to work. I just ordered a better router hoping to get through this situation. I am setting this system up for learning purposes.

    Any thoughts or suggestions, perhaps on which routers and firmware to use. I am very familiar with setting up BBMD's, it could be easier. But I am missing the secret sauce to get the information through IP routers.

  2. #2
    Join Date
    Nov 2006
    Location
    SE Wisconsin
    Posts
    495
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    Port blocking by default in the routers? What ports is your system using?

    That's the first thing coming to mind in 30 seconds, anyway.

    Ken

  3. #3
    Join Date
    Jan 2019
    Posts
    3
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    Thread Starter
    The most common ports are 47808 and 47806.

  4. #4
    Join Date
    Oct 2018
    Location
    WI
    Posts
    13
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    You should try simplifying your setup. To have two subnets, you do not need two routers, you only need one. The router will have one or more LAN ports and a WAN port. You should configure the router's LAN side to be one subnet, for example 192.168.11.0/24, and configure the router's WAN side to be the other subnet, 192.1.10.0/24. If possible, you will also want to disable NAT on the router to simplify things.

    You would then connect one BBMD to the LAN side of the router on the 192.168.11.0/24 subnet with its default gateway set to the router's LAN IP address and you would connect another BBMD to the router's WAN port on the 192.1.10.0/24 subnet with its default gateway set to the router's WAN IP address. You can then configure the BDT tables on each BBMD as you normally would by putting both BBMD's IP addresses in each.

    If you must use NAT with your router, you will need to add port forwarding from the WAN side to the LAN side so that packets coming in on the WAN port can traverse the router and get to the BBMD device on the LAN side. Also when using NAT, your BBMD must be capable of supporting NAT and you will need to use the router's WAN IP address instead of the IP address of the BBMD on the LAN side when configuring your BDT tables.

  5. #5
    Join Date
    Mar 2016
    Posts
    40
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    Quote Originally Posted by jschulze View Post
    You should try simplifying your setup. To have two subnets, you do not need two routers, you only need one.
    I agree with this, it'll make everything easier. I recently did some port forwarding to reach a Modbus device on a different subnet. I was sure my router config was good (and I was testing with a cheapo linksys) but couldn't make it work. Long story short check you default gateway. The server receiving the forwarded ports needs to have the proper default gateway so it's responses make it back out to the WAN.

  6. #6
    Join Date
    Apr 2019
    Location
    Northern New mexico
    Posts
    1
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    are your test routers exchanging routes?

  7. #7
    Join Date
    May 2009
    Location
    SC
    Posts
    1,628
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    Back in the day when I was doing this I also used some ancient lynksys routers. You have to do a little work to dumb them down so you don't have a NAT situation between those subnets. Eventually I did get spanning tree working on them but I think that's the issue with your setup. Get rid of Network Address Translation firewall and maybe try looking for spanning tree.
    Scott Jalbert
    WebCTRL ninja
    AX and Smartstruxure newb
    SiteScan Retired

    • Please be careful. There’s a lot of things in here that we’ll have to fix after they finish killing you.
    • The S in IoT stands for Security
    • “Well,” he sighed to no one in particular, and looked up into yet another alien sky. “Here we are again.”

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