Networking question, for a friend...



  • it has been a while since I have been on the networking train so I just want to confirm a hunch before I make myself look stupid...here's the sitch

    Client computer (on metal working machine) has 2 nics. one it uses to communicate with the innerds of the machine and pass commands back and forth and the other is to connect to the coporate network for file sharing and what-not. each works independently but not together. it seems that when both are plugged in the machine commands get routed to the corporate network thus rending the machine useless. they swear that other MFG machines work fine this way. My conclusion was IP addressing.
    Here is the thing,
    nic one (machine) is 192.168.0.1 subnet 255.255.255.0
    nic two (corp) is 192.168.1.x subnet 255.255.255.0

    What I think may be happening is that the MSP that set up nic 2 for the corp network gave it a /24 subnet when in fact the corporate network is /16 and has some default route for 192.168.x.x addresses? am I wrong or is this pretty much the only thing that makes sense?



  • @kimberlin said in Networking question, for a friend...:

    it has been a while since I have been on the networking train so I just want to confirm a hunch before I make myself look stupid...here's the sitch

    Client computer (on metal working machine) has 2 nics. one it uses to communicate with the innerds of the machine and pass commands back and forth and the other is to connect to the coporate network for file sharing and what-not. each works independently but not together. it seems that when both are plugged in the machine commands get routed to the corporate network thus rending the machine useless. they swear that other MFG machines work fine this way. My conclusion was IP addressing.
    Here is the thing,
    nic one (machine) is 192.168.0.1 subnet 255.255.255.0
    nic two (corp) is 192.168.1.x subnet 255.255.255.0

    What I think may be happening is that the MSP that set up nic 2 for the corp network gave it a /24 subnet when in fact the corporate network is /16 and has some default route for 192.168.x.x addresses? am I wrong or is this pretty much the only thing that makes sense?

    The corp net is 192.168.1.0/16 and of the client machines NICs is 192.168.0.0/24?

    Gremlins. Don't get bitten. Your corps net network address is 192.168.0.0, so you have overlapping ranges. The client machine will have a very hard time when in needs to transmit packets. Better reconfigure the machine network, if possible.



  • @thwr the corp NIC is 255.255.255.0 so /24 but I am proposing that perhaps the corp network is /16. I don't know what the corp subnet is, you have about all the info I do. I'm trying to help someone that is in over their head on the machine side and going a bit blind. The customer's msp doesn't seem to know what they are talking about. My question is how on earth could traffic from the machine be going over the corp network if the corp subnet really is 255.255.255.0?



  • Oh, wait. Both NICs have /24 subnet masks. Should work, in theory, but it is so far away from anything sane that I wouldn't even think about doing something like that.

    Better get a proper configuration before trying to fix an ugly workaround



  • @kimberlin said in Networking question, for a friend...:

    @thwr the corp NIC is 255.255.255.0 so /24 but I am proposing that perhaps the corp network is /16. I don't know what the corp subnet is, you have about all the info I do. I'm trying to help someone that is in over their head on the machine side and going a bit blind. The customer's msp doesn't seem to know what they are talking about. My question is how on earth could traffic from the machine be going over the corp network if the corp subnet really is 255.255.255.0?

    Ok, what traffic gets forwarded to the corp net? From some machine behind your client PC?



  • @thwr I don't think it is insane, it is one machine that needs to be connected to 2 different networks, shouldn't be an issue but it is and they are trying to figure out why it isn't working like it should. My stuff about the possible /16 route was just a guess. If the domain added a /16 route the machine would think that 192.168.1.1 and 192.168.0.1 should be routed the same but they shouldn't. If the route was /24 it should see them as completely different networks and they should never cross.



  • Are you using a single / common default gateway?



  • @thwr 2 nics on the client. One communicates commands from the computer to a "robot" and vice versa. the other is connected to the corporate network so they can share the "robot" config files.



  • @kimberlin said in Networking question, for a friend...:

    @thwr I don't think it is insane, it is one machine that needs to be connected to 2 different networks, shouldn't be an issue but it is and they are trying to figure out why it isn't working like it should. My stuff about the possible /16 route was just a guess. If the domain added a /16 route the machine would think that 192.168.1.1 and 192.168.0.1 should be routed the same but they shouldn't. If the route was /24 it should see them as completely different networks and they should never cross.

    It would have been insane if we are actually talking about overlapping ranges, but it doesn't looks like that.



  • @scotth there is not a "regular" network for nic 1. It is a simple communication network between the computer and a command board.



  • The problem is the salesman that got tied up in this doesn't know how to tell the MSP what to do to fix it and they are blaming the $100,000 machine for not working when I don't think it is the machine's fault. I'm in WA and the machine is in IL so I can't run out there and check their network...I offered 🙂



  • @kimberlin said in Networking question, for a friend...:

    @scotth there is not a "regular" network for nic 1. It is a simple communication network between the computer and a command board.

    Thinking this through, you're using an IP network capable device. In order to talk they both will have an address. I'm thinking you may at least bandaid this by setting NIC1's default gateway to the machine (command board). Just a guess.



  • @scotth yeah, i'm with you. My thought was to see if they could change the machine IP to 172.whatever to get it the heck out of any kind of possible routing issue.



  • then we would have a 172.x.x.x and a 192.x.x.x so there is no way they are going to talk, which is what we want



  • @kimberlin said in Networking question, for a friend...:

    @scotth yeah, i'm with you. My thought was to see if they could change the machine IP to 172.whatever to get it the heck out of any kind of possible routing issue.

    That's what I would try. Just to be sure.

    Is there by any chance "internet sharing" active on the client PC? This effectively turns that PC into a router. Just an idea.



  • @thwr it would be a longshot, there would be no reason they would have turned it on. I just keep going back to there having to be a route for all 192.168.x.x traffic to go elsewhere. that is the only thing i can think of that would snipe the traffic off that nic.



  • @thwr thanks for talking through this with me BTW. been a while since i ran in the networking world.



  • @kimberlin said in Networking question, for a friend...:

    My question is how on earth could traffic from the machine be going over the corp network if the corp subnet really is 255.255.255.0?

    This will work if the default gateway is within /24 of the IP of the PC. i.e. if the default gateway is something like 192.168.1.254, that is within range of the 255.255.255.0 subnet and would allow the PC to connect.



  • @kimberlin said in Networking question, for a friend...:

    then we would have a 172.x.x.x and a 192.x.x.x so there is no way they are going to talk, which is what we want

    Sure, but make sure you only set a Default gateway on the corp NIC.



  • Question - Why is the corporate side not using DHCP?

    Assuming DHCP is available on the corp network, turn that on, make sure there is no default gateway on the device network adapter. Then check the settings. You should be able to know the subnet mask right away with the assigned info.



  • @kimberlin said in Networking question, for a friend...:

    @thwr thanks for talking through this with me BTW. been a while since i ran in the networking world.

    my pleasure



  • @kimberlin said in Networking question, for a friend...:

    @thwr it would be a longshot, there would be no reason they would have turned it on. I just keep going back to there having to be a route for all 192.168.x.x traffic to go elsewhere. that is the only thing i can think of that would snipe the traffic off that nic.

    Was just a wild guess



  • @dashrender Agreed, i doubt it is DHCP and to answer why, i don't know, can't see it. Their MSP is just playing blame game i was trying to posit a solution without having all the data. If those things are each on 255.255.255.0 subnets though, no way they can talk without something routing it.