Will changing the local DNS settings increase network transfer speeds?

I would replace that first Switch with a router. And then I could create a subnet off of that? Then I would have internet access and a faster local network because my local traffic is never reaching the ISP gateway?

If your Gigabit switch is operating correctly, none of the "local" traffic (everything that is connected to the switch) is reaching the ISP gateway. The only traffic that reaches the gateway is the Internet connection.

So, no advantage to replacing the switch with a router as far as "local" traffic is concerned.

My question is this: if I change the local DNS setting from the ISP gateway router to the Airport in my kitchen, will that increase my local network transfer speeds? I'm thinking the line between the gateway and my kitchen router is a bottleneck, if my understanding is correct that all traffic needs to flow both directions to and from that gateway router since it's the default DNS. Or am I misunderstanding something?

Changing the DNS servers will have no impact on performance over your local network. All connections between devices on your network are at the Layer-2 level of the OSI model. That being said, all of that traffic will only go through the Layer-2 Ethernet switch portion of your gateway device, not the Layer-3 router portion. What could affect performance at this level could be one of the following three things:

1. A faulty or misconfigured Ethernet card (NIC) in the host device.
2. A faulty Ethernet switch.
3. The Ethernet cable between connections. Also keep in mind that that maximum total run length for Cat 5e is 100 meters, unless you use switches.

My question is this: if I change the local DNS setting from the ISP gateway router to the Airport in my kitchen, will that increase my local network transfer speeds?

No, since the AirPort is already using the same DNS information that your gateway router is using. It won't hurt to change the setting on the AirPort if you want, but it won't help either.

You don't mention what kind of speeds that the shared router provides to the network, but with two families doing normal things, it would need to be at least 40-50 Mbps, preferably higher. If you want to watch movies online, then you will need 100-150 Mbps or more.

Probably more than you want to know, but the AirPort is using DNS settings that reference the local LAN IP address of your router, which is using the DNS servers that the ISP provides. So this simply means that the AirPort....and everything else on your section of the network......is already using the same DNS servers as the gateway router.

Due to the way Bonjour works it is best to have local DNS gateway and not the ISP .. which should be set on the main router WAN configuration.

What will really slow things down is your local network having any 100Mbit instead of gigabit segments.

1000Mbit is still fast enough for most home users.. and cost of the next standard 10Gbit is huge for now.

So check on all the devices that they are gigabit.

On a home network if you do have a slow router or switch replace it for one with gigabit.

Mostly as Tesserax pointed out, your network will use only the switch part (layer 2) of the routers.. unless you have actually made a mistake and used double NAT somewhere.

I have very occasionally seen issues where a main network router, limited to 100mbit causing slow down of network because all packets were routed via the main router.. this is a flaw that is usually easily sorted by sticking a gigabit switch between the slow router and the rest of the network.. so only one connection is plugged via the switch.. and only packets routed to internet will pass through it.

Thanks for that explanation. I guess I don't really know the right questions to ask. I assumed since each device is set with a DNS entry, and that seems to always be the gateway's address, not the ISP DNS, that the DNS setting determined which device directs all the traffic.

By default, each network device is a DHCP client. As such, it gets its IP address information, including where to find the default router and DNS servers, from a DHCP server. That server, is most likely, your ISP-provided gateway device ... thus why each device is "told" that the gateway is to where to look for DNS service. In turn, your gateway is getting its IP addresses from your ISP ... as it too, most likely, is configured as a DHCP client.

Hopefully, I didn't add to the confusion there.

That's my real question then: if I transfer data between two devices that are connected to a router that's downstream from the gateway, does that traffic go all the way to the gateway and back to the router, based on some setting (DHCP? "Router" address in network settings? NAT? something else?), and can I change that setting so that the router in my kitchen is the traffic cop rather than the gateway?

Again, for any devices on your local network "behind that gateway," the gateway's built-in Ethernet switch is doing all the work to move data between these devices. Yes, the data it going "through" the router, but only the switch portion. Neither DHCP nor NAT comes into play. Each network device has a pre-defined MAC (hardware) address. The switch "remembers" these addresses and to which port on the switch they are connected to. IP addresses are not used at all in this case, just the MAC addresses are required to move data between devices. Staying awake? Sorry, I know this can get really boring quickly.

Only when a device needs to access another device that is NOT on the same local network, do IP addresses matter ... and this is where the router portion of the gateway has the work cut out for it. The router, similar to the switch, keeps track of a device that is sending data through it, but instead of keeping track of MAC addresses, it keeps track of IP addresses.

Where DNS comes into the scene, is to think of this service as the Internet's version of the Yellow Pages. DNS keeps track of a site's URL (aka, www.apple.com) and its actual IP address (XXX.XXX.XXX.XXX). URLs are intended for humans as computers only understand the equivalent IP address, otherwise, you would need to use the site's IP address to access it.

So where DNS does have an effect is getting to Internet web sites. Some DNS servers do a better job at getting you there quickly ... and your ISP-provided ones may not be the best available for you to use for this. That's why you can try the Google DNS or OpenDNS servers to see if they help improve your access to Internet sites.

I'm wondering how to isolate my side of the house/studio so local network traffic doesn't flow to/from the ISP Gateway, without cutting off my internet access, and without disturbing the network on the other side of the house

You are asking about setting up a separate "Subnet". Which AirPort(s) handle your side of the house? Socknet AE2? Socknet TC1? Both?

In other words, if you could set up an "isolated" network that would allow the AirPort or TC to connect to the Internet, but not "see" any of the devices on any of the other AirPorts.....and conversely, devices on any of the other AirPorts would not be able to "see" any of the devices on your "isolated" network.......which AirPort or TC would you chose for this setup?

So basically I'm wondering how to isolate my side of the house/studio so local network traffic doesn't flow to/from the ISP Gateway, without cutting off my internet access, and without disturbing the network on the other side of the house. I thought about replacing the Gigabit Switch with a router and designating it... this is where I need the help with which setting to use.

To accomplish network separation, as Bob has mentioned, you need to create a separate subnet for devices on "your" side of this network. You can do this if: 1) Your gateway supports VLANs, and 2) You employ managed Ethernet switches .,.at least one, where you currently have the Gigabit switch located. Further you can create VLANs for both your wife and your kids devices.

Finally, if you want your wireless network to support multiple SSIDs, you would need to use managed Access Points for that as well. For example, socknet TC1 would be replaces with a Ubiquiti UniFi AP-AC-Pro and broadcast multiple separate wireless networks for guests and your family.