Network Setup Question

[stgislander]

Okay, I need some help from you IT folks.

On my software development PC I have two NICs. First NIC is my connection to the Internet. The second is my software development connection to a small network of National Instruments controllers. The NI controllers need to connect to NI's software server for downloading updates. In my current setup, those controllers cannot see the Internet.

I'm not sure I have the correct terminology, but how do I setup my NICs so the NI controllers can see the Internet? Is that done by creating a Bridge Connection?

 

[Sneakers]

Are both NICs setup to use the same subnet address? Plug them both into a smart switch, then connect the smart switch to the iNet. The smart switch should prevent circular forwarding.

If you don't want the two controllers to talk to each other, use different subnets, tie them to a smart switch, and then the switch to your router. The router should forward packets from both subnets to the iNet.

 

[stgislander]

Looking at ipconfig, they are both on the same subnet. 0

 

[HemiHauler]

Okay, I need some help from you IT folks.

On my software development PC I have two NICs. First NIC is my connection to the Internet. The second is my software development connection to a small network of National Instruments controllers. The NI controllers need to connect to NI's software server for downloading updates. In my current setup, those controllers cannot see the Internet.

I'm not sure I have the correct terminology, but how do I setup my NICs so the NI controllers can see the Internet? Is that done by creating a Bridge Connection?

Assuming your OS is windows, paste up the output of “route print” and “ipconfig /all” in a cmd window.

Your dev network likely doesn’t have a route to the internet.

 

[stgislander]

Are both NICs setup to use the same subnet address? Plug them both into a smart switch, then connect the smart switch to the iNet. The smart switch should prevent circular forwarding.

If you don't want the two controllers to talk to each other, use different subnets, tie them to a smart switch, and then the switch to your router. The router should forward packets from both subnets to the iNet.

I am guessing by a smart switch you mean a managed switch?

 

[Sneakers]

I am guessing by a smart switch you mean a managed switch?

No, a smart switch is in-between a plain vanilla switch and a managed switch. You don't manage it, but it has intelligence when it forwards packets so the net doesn't get flooded with something that doesn't need to be forwarded to a particular port on the switch. A plain vanilla switch just forwards everything to everywhere regardless.

 

[Clem72]

Probably a million ways to skin this cat. As sneakers said, if you want the development network to basically always be online then just run both NICs into a switch (or both lines into the switch and only one back to a single nic in your computer).

But if you don't want to make any physical changes the easiest might be to make the default gateway of your development nic the IP of your other NIC. Or add a static route for your dev nic to send all L3 traffic to the internet nic which is effectively the same thing.

 

[stgislander]

No, a smart switch is in-between a plain vanilla switch and a managed switch. You don't manage it, but it has intelligence when it forwards packets so the net doesn't get flooded with something that doesn't need to be forwarded to a particular port on the switch. A plain vanilla switch just forwards everything to everywhere regardless.

plain vanilla switch = hub

 

[Clem72]

I am guessing by a smart switch you mean a managed switch?

No smarts needed, hell you don't even need a switch if they are on the same subnet you could use a hub. But the cheapest switch you can buy would work unless your computer NIC is connected directly to your modem instead of a router, in which case you would need a router/switch (I guess you could call that a smart switch).

 

[HemiHauler]

No, a smart switch is in-between a plain vanilla switch and a managed switch. You don't manage it, but it has intelligence when it forwards packets so the net doesn't get flooded with something that doesn't need to be forwarded to a particular port on the switch. A plain vanilla switch just forwards everything to everywhere regardless.

You’re describing the difference between a hub and a switch. The “smart” switch you describe likely just keeps a cache of what layer 2 addresses were seen on which port and doesn’t have to ARP for it next time, ie, a switch.

 

[Sneakers]

But if you don't want to make any physical changes the easiest might be to make the default gateway of your development nic the IP of your other NIC. Or add a static route for your dev nic to send all L3 traffic to the internet nic which is effectively the same thing.

You could, but I like to keep router functions off the PC, steal too many cycles.

 

[Clem72]

plain vanilla switch = hub

eh, kinda. A switch directs traffic based on your MAC instead of your IP so it allows for more efficient use of resources, faster comms, more isolation (security). And switches can be Layer 3 as well and provide some routing capability. Everything on a hub is seen by everything else.

Think of it like a switch is a telephone switch (the old style), everyone is calling the operator who connects you to who you need to talk to. A hub is like a using a megaphone.

 

[Sneakers]

You’re describing the difference between a hub and a switch. The “smart” switch you describe likely just keeps a cache of what layer 2 addresses were seen on which port and doesn’t have to ARP for it next time, ie, a switch.

A smart switch tables what addresses it sees on what ports and does not forward packets unless it knows where it's being forwarded to, after learning.

 

[HemiHauler]

A smart switch tables what addresses it sees on what ports and does not forward packets unless it knows where it's being forwarded to, after learning.

Exactly. That’s a switch.

 

[Clem72]

plain vanilla switch = hub

I re-read your quote of sneakers and yes, what he is describing as a vanilla switch sounds like a hub. It's almost a moot point, it's hard to find hubs anyways.

 

[Sneakers]

Exactly. That’s a switch.

But it's not a managed switch, which was the point.

 

[Clem72]

Exactly. That’s a switch.

That's just a switch. It's the literal definition, switching packets based on L2 addressing. Nothing smart about it.

 

[HemiHauler]

eh, kinda. A switch directs traffic based on your MAC instead of your IP so it allows for more efficient use of resources, faster comms, more isolation (security). And switches can be Layer 3 as well and provide some routing capability. Everything on a hub is seen by everything else.

Think of it like a switch is a telephone switch (the old style), everyone is calling the operator who connects you to who you need to talk to. A hub is like a using a megaphone.

Run a packet sniffer/tcpdump on a hub network (shared media) and a switched network and this can be observed directly.

 

[stgislander]

Probably a million ways to skin this cat. As sneakers said, if you want the development network to basically always be online then just run both NICs into a switch (or both lines into the switch and only one back to a single nic in your computer).

But if you don't want to make any physical changes the easiest might be to make the default gateway of your development nic the IP of your other NIC. Or add a static route for your dev nic to send all L3 traffic to the internet nic which is effectively the same thing.

Okay, setting the gateway address of my dev NIC to the IP of my Internet NIC did not work. Those NI controllers still can not see the Internet.
Explain the static route thing?

 

[HemiHauler]

But it's not a managed switch, which was the point.

All switches have a layer 2 table with some lifetime on the cache. This reduces the need for arp who-has requests, and thus reduces network traffic. This is not a feature of a “smart switch”. It’s a feature of a switch (vs. a hub).