router to subnet network

[lowbot]

Perhaps I am looking at this problem incorrectly. Please correct my assumptions if need be.

My company is expanding and I'd like to add a subnet because we are running out of IPs. Our original subnet is 10.10.8.x 255/255/255/0.

Id like to add 10.10.9.x. I am thinking the only way to do this is to get a router to create a subnet. id like this subnet to receive and send broadcasts to the 10.10.8.x subnet.

This router will be about 100ft away from our main switch and other router so I will run CAT6 and Id like to get 1gbps between the subnets.

Can someone recommend a cisco product that can handle 1gbps? Is there a way to do this without adding another router? Any advice would be appreciated. Thanks

 

[silverhairb]

In terms of spanning that 100ft. distance, you might want to consider putting a simple gigabit switch at about the halfway point. It could be a small relative cheapie since its not really going to do anything except pass the signal, but it will minimize signal degradation, if that's a problem.

(I have to preface this by saying that I'm not completely sure of the following, I'm no subnet expert.) Would going to a class b subnet take care of the problem? Or maybe a subnet mask of 255.255.240.0 (20-bit)? If I understand subnet masking correctly, I think that would allow host addresses in the range of 10.10.0.1 through 10.10.15.254 on the same ([sub]network.

Would appreciate if somebody who knows what they're talking about could verify that.

[the other] Bill

 

[burtsbees]

Close Bill---wrong octet, though...255.255.240.0, not 255.255.255.240---that would give 14 hosts per subnet. Also, putting everything into one subnet would not separate traffic...however, this is what I would also suggest, since broadcasts are not passed beyond network boundaries unless specifically commanded to.
Lowbot---just because a router/switch/etc has a gigabit interface, only the high end devices actually get that kind of throughput, especially routers. Let's start off by discussing what you have right now (manufacturers)---my thought would be to subnet into vlans, if your switch supports vlans. If it is a layer 2 switch only, you would need the router to route between the vlans. Something tells me that you have more than one switch if an entire subnet of 254 hosts is taken up...Bill---this would be a lot of work to change the mask on 254 hosts (well, not THAT much), but I agree that it would be a better solution if lowbot is simply running out of hosts.

Burt

 

[silverhairb]

Burt, maybe I'm getting cross-eyed in my old age, but I think I suggested the mask of 255.255.240.0 (a 20-bit mask). Wouldn't that give over 3500 hosts on the same subnet?

Good point on the gigabit link. But maybe consider that if there are a lot of PCs on one end of the building passing through that one wire, it might be nice to have that big pipe to limit contention. But it would also need a gigabit switch at each end of that long run. Three switches in total. If its mostly used for internet access, then I agree that gigabit probably really necessary.

It would be a lot of work to convert. Isn't that called job security? lol.

[the other] Bill

 

[lowbot]

Thanks for all the excellent and informative replies.

My understanding of subnetting could be better, but it looks like switching the subnet from 255.255.255.0 to 255.255.240.0 will give me a 20-bit address space which is 4000 or so hosts.

How would I safely implement this in a network environment? Im assuming that if I change the subnet mask on all my machines then I should be okay. What happens if I miss a machine or two? Or would I just change the subnet mask on the new machines but leave the old ones with 255.255.255.0.

Do all pieces of network equipment need this change too?

Thanks again!

 

[silverhairb]

Actually you get 12 bits of host address space 20 bits of network address space. That would be over 3500 host addresses.

The machines that use 255.255.255.0 mask would be able to reach the other 252 devices on their class c subnet (e.g. 10.10.8.0 255.255.255.0 network,). They would not be able to communicate with the addresses on a different subnet (e.g. 10.10.9.0 255.255.240.0 network). For example, a machine with an address of 10.10.8.61 with a mask of 255.255.255.0 would not be able to communicate with machines with addresses on a 10.10.9.238. Once the mask changes to 255.255.240.0 on the older machine, it would be able to communicate.

The conversion would not knock the existing machines off the network (as long as the router address does not change), they would just have no communication with newer machines under the new addressing scheme until the mask is updated. So update the masks on the servers first. Then schedule the rest of the existing machines for mask update as time and business needs require.

At least that's my 2 cents worth. (Sticking me neck out a little.)


[the other] Bill

 

[burtsbees]

Holy crap, I am blind...I'm going to bed...nighty-night...lol

Burt

 

[silverhairb]

No problemo. You're still the master, I'm still the humble grasshopper.

Never hurts for me to go back to the book and study a little more. I thought I had missed something.


[the other] Bill

 

[Linkers]

I would go for a Layer 3 Cisco switch (like 3550 etc) for inter VLAN routing which is 100 times faster than a router on a stick.

 

[unclerico]

I've got to chime in here and offer my .000002. You really, really need to understand your traffic patterns and the load that they create before you expand your nework to accomodate roughly 4094 hosts. Best practices will recommend no more than 500 hosts on a single subnet especially if you're network relies heavily on broadcast traffic and/or chatty protocols such as CIFS. IMHO, do what Linkers suggests and get a layer 3 switch. Create some VLAN's and create a nice clean network topology. You need to be sure that you are planning for redundancy in the remote area so that if you lose whatever device is in the middle those people connected will not be left in the dark. Also, when it comes down to choosing the type of cable to run you may want to look at running fiber to lessen the impact of noise/interference when dealing with lights, machinery, etc.

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
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[vipergg]

I agree anything over 500 hosts is asking for trouble and creates a huge broadcast domain and if you have a problem then every one of the 500 users will be down , break it up into 2 /24's . Also you would not have to run around to the current users and change all the subnet masks unless you are using dhcp in which case it doesn't matter. Does your current router have any spare interfaces , if so just run the new subnet off that though no router is going to give you gig thruput short of something like a 7600 . If this is a company get them to cough up for a layer 3 switch and everything will be a lot easier and you can get gig thruput.

 

[lowbot]

Thanks again for the excellent replies!

FWIW, We're not adding 500+ hosts, but we may be hitting the 254 limit sooner than later and Im exploring options. Most of these machines are low-bandwidth kiosk machines.

> So update the masks on the servers first. Then schedule the rest of the existing machines for mask update as time and business needs require.


Im assuming that I should also do any routers and network equipment first. Also, Im assuming that just changing the subnet mask will not require adding a vlan or a router. The subnet will simply expand and run on the same LAN, correct?

 

[unclerico]

If you have a large server and hardware appliance population making changes to the networking info will require scheduled downtime. Have you thought of keeping all servers and hardware appliances on the current subnet, but then create a new subnet for workstations and change the DHCP scope accordingly?? Doing it this way will only require your users to reboot their machine's and will require no downtime. Just a thought...

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)