Network Hardware Advice (Switch on ADSL)

Hi there guys, I am looking for advice about best hardware for my new network. At the moment I have an office with combined ASDL Wireless Router with 4 ethernet ports. It has built in Firewall, NAT, DHCP etc. At the moment we are using all 4 ports and also have 2 wireless clients connected to the router.

We are moving to a new office and I want to get the entire network wired. I was searching Netgears products for a ASDL Router with 16 ethernet ports, but I cannot find such a product so a assume i would need to get something like a Cable/DSL High-Speed VPN Firewall Router and then connect a switch to this. As you can probably see I am a bit confused, especially as my current ADSL Router has an RJ11 connector and I am unsure how I would be able to connect this to a RJ45 port on a new switch or Router.

Any help or advice would be a big help. Basically, I want to have the ability to have 16 devices connected to my network and also the Internet.

Many thanks,
Paul

 

so i could just buy a standard 16 port switch and plug into the ethernet port on my router and then that would be it? So would something like the NETGEAR JFS516 Switch with 16 ports meet my needs?

 

Try to get a single switch that will have enough capacity to cope will all the computers on your network and any near future expansion. As a rule of thumb, count how many ports you need now, and double it. Base your switch size on that figure. So if you have 10 computers, you should aim for a switch with at least a 20 port capacity. That will support your current requirement and leave you plenty of capacity for furture growth.

So a netgear 16 port siwitch would be fine if you have less than 10 computers. If you have ten or more, I'd recommend you go for a 24 port switch. Also I'd recommend going for a managed switch if you can afford it. The extra trouble-shooting options you get with a managed switch is well worth the extra cost in my opinion. Personally I am fan of HP Procurve switches.

Also hubs and switched need to be connected together via a cross-over. You can either use a cross-over cable, or a dedicated port (usually port 1) that can be switched between cross-over and straight through mode. Some modern switches have auto-sensing cross-over/straight-through systems that negate this problem, but you should be aware of it in case your switches don't.

<pedantic hat on>
Actually, you cannot daisy chain hubs indefinitely as there is a letancy issue.

One of the requirements of a shared ethernet network is that when a transmitting node sends a packet of data out, it will listen for a collision while it is sending. If it receives no indication of a collision while it is transmitting, it will assume that the data has been sent correctly. For this to work the transmitter has to send data out for a period long enough for the furthest node on the network to send back a collision notification before transmission ends. It is this function that limits both the maximum length of an ethernet network and the minimum data frame size.

Hubs add latency. There is a very short delay between the hub receiving the data and it being tranmitted by the hub. If you add a second hub, the latency becomes almost large enough that you would break the ethernet collision rule. To cope with this, the connection has to be short between the hubs. If you add a third hub, collisions don't get reported correctly and you start dropping packets.

This is important to understand because it is very difficult to diagnose the fault. The symptoms are odd network behaviour. Basically you start losing data packets in a way that Ethernet isn't able to automatically detect. Therefore, you have network faults, but systems that believe everything is OK.

With 10Mb/s hubs transmission speeds were lower and therefore the trransmitting nodes had longer to send data. So at 10Mb/s this wasn't much of an issue. You could daisy chain 3 or 4 hubs together without much of a problem. However, 100Mb/s hubs changed that. You can only daisy chain two 100Mb/s hub together before you get collision/latency problems.

I've seen a couple of examples of this. The worst was where someone had created a 16 node network by daisy chaining 4 port hubs together.

Switches are different. Each connection between switches is in effect a seperate Ethernet network. You still get latency issues (which tends to be why on a quiet network hubs are faster than switches), but they don't causes the issues you had with 100Mb/s hubs.

To overcome this problem in the days of hubs, (when switches cost thousands of pounds each) a system called "stacking" was created. This allowed hubs to be connected together via a special high speed link between their backbones. This allowed you to add five or six hubs together and have them act as a single hub.

Stacking and daisy-chaining are different. Daisy-chained hubs are connected via normal or cross-over ethernet cables. Stacked hubs are connected by special dedicated stacking cables. Only the more expensive "stackable" hubs supported this feature.

This is a pedantic point nowadays as it is hard to buy hubs. Switches are so cheap you might as well get them rather than hubs.

The upper limit comes from how many systems you can have broadcasting on a network before you start getting performance issues. The 255 is a rule of thumb for system running NetBIOS (in effect all windows systems). If you have more than 250 computers on a network, you should consider splitting it into seperate "broadcast domains ". You use routers or layer 3 switches (also called routing switches or multi-port switches) to join separate broadcast domains together.
</pedantic hat on>

 

Thanks for your replies, at the moment i will need 8 ports so i am getting a 16 port switch as recommended to cope with expansion. Could someone tell me if I would I need to disable the Router’s DHCP, Firewall, NAT, Port forwarding and let the new switch do all this instead?

At present the router is my default gateway, so would I now make my switch the default gateway?

 

A switch will not provide any of those services, so stick with the router providing them. A switch simply connects all the devices together and allows them to communicate to one another.

 

Tony, glad you found my ramblings of some interest.

Yes, I agree that if budget is tight two smaller switches would work.

However, the connection between the two switches (either direct or via the router) is a bottleneck being limited to 100 Mb/s plus the added latency of the intermediary devices. So a single larger switch (where all ports are connected via a backbone within the switch, which connects them at in excess of 1Gb/s) will provide better performance.

In conclusion, if you can afford it, a large switch will provide better performance, but if you can't two smaller switches will do the job.

As griffmaster only needs 8 ports now, the 16 port switch he's intending to buy sounds fine.

 

so if i get a switch then i can just plug all my devices into the switch and then the switch to the router and I wont need to reconfigure all my IP addresses on my network?

 

I would guess that there is little/no benefit in having 3 devices connected to the router and 6 connected via the switch? Compared to having the switch connected to the router and all 9 devices connected to the switch?

 

ReggieB

all the current switches i have used have the auto detect mode which allows you to just use a straight through patch cable. should be no need for a cross over cable with dlink or linksys. ive used both with a normal patch cable.

 

Yes, auto-detect is common nowadays, but I don't think it is so universal as to ignore the issue. It's something you need to be aware of if you have problems connecting hub/switches. I guess the advice nowadays should be "a cross-over will always connect hubs and switches, but a straight through can usually be used instead." In other words, most of the time you'll be fine with a straight through, but keep a cross-over in your toolbox for those odd occasions when you have to fall back on the basic system.