[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

How many nodes are acceptable on a vlan?

Posted on 2009-02-10
7
Medium Priority
?
1,039 Views
Last Modified: 2012-05-06
We have several vlans... one for each building.  One building is using up almost all available IP addresses.  Currently the subnet mask is 255.255.254.0 so we have a total of 508 usable addresses.  We have 2 options, add another vlan to the building or change the subnet mask to allow more IP addresses.

For manageability, it would be preferable for us to change the subnet mask and up the number of available hosts on the subnet.  The thing I'm wondering is what number of nodes would be acceptable to have on a vlan?  We have a Cisco 4006 and I want to make sure we do not impede performance.
0
Comment
Question by:bpl5000
7 Comments
 
LVL 12

Expert Comment

by:piattnd
ID: 23603901
There's no limit to the number of nodes on a VLAN.  The only limitation will be the number of IP addresses available for you to use.  You will just need to make sure your routers have the ability to communicate between the VLANs.

Think of a VLAN as a LAN, as it is just a virtual LAN.  The only limitation to a LAN is the number of available IP addresses.  I will say though, if you have 1,000 hosts, I wouldn't recommend using a home router to handle the routing! ;-)

Moral of the story, the speed of your hardware will determine how many nodes your network equipment can handle, but that doesn't have anything to do with VLANs.
0
 
LVL 43

Expert Comment

by:JFrederick29
ID: 23603956
Just to add as a second bit or reassurance.

Changing the mask is fine.  We use /22 masks in our buildings.
0
 
LVL 12

Accepted Solution

by:
jjmartineziii earned 1200 total points
ID: 23603987
There is no limit on nodes, but do be aware that large broadcast domains will slow a network down.

I would break it up into domains as small as logically possible.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 5

Author Comment

by:bpl5000
ID: 23604177
Piattnd, like I mentioned, we have a Cisco 4006, not a home router.  I was looking for people with Cisco experience (I should have mention that).  We will have 700+ devices and maybe up to 1,000 someday.  I know PC usage and things like that make a difference too, but I'm wondering if there is any general type of guideline for how many nodes should be limited to a vlan.

We are strictly using TCP/IP.  No servers or databases are contained within this vlan.

JFrederick, approx. how many nodes do you have in your environment?
0
 
LVL 43

Assisted Solution

by:JFrederick29
JFrederick29 earned 800 total points
ID: 23604316
Best practice would be to have /24 subnets and route between them.  With hardware today and non-broadcast apps, there really is no performance/useability downside to routing between subnets.  The issues come in with management like you said (DHCP reservations, moves, IP filters/restrictions, etc...).  It would be simpler to have one large subnet but its cleaner and more desirable to have smaller subnets/broadcast domains.  It's a tradeoff between performance (NIC's processing lots of ARP traffic) and ease of management.

If you are truly planning to have 1000 devices in one VLAN, I would take this opportunity to break it out into multiple VLANs.
0
 
LVL 50

Expert Comment

by:Don Johnston
ID: 23604467
The rule of thumb for VLAN size is no more than 20% broadcast traffic. So as long as the broadcast don't exceed 20% of the total traffic on the VLAN, it's not too big.


0
 
LVL 5

Author Comment

by:bpl5000
ID: 23623983
I read something similar that stated the 20% broadcast rule when determining size, but to me that makes no sense.  For example, let's say I have a subnet of 255 hosts with 20% broadcast traffic, then I double the subnet to 510.  If the 255 hosts that I added broadcast very little, but create a lot of other traffic, then the broadcast percentage would go down even though the vlan size has decreased.

I contacted Cisco and the engineer's recommendation was this...
-Up to 500 hosts if speakers are only using TCP/IP and fairly quiet
-Up to 300 hosts if using Suns, or NetBIOS over TCP on PC's
-Up to 200 hosts if using AppleTalk or DECnet

Of course there is no rule written in stone since it depends on variables that will differ from one network to another.  However, I believe JFrederick is correct when he says that smaller is better when considering performance.  We have now decided to keep the subnets at the current size and just add an additional subnet.

Thanks for the help!
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

It happens many times that access list (ACL) have to be applied to outgoing router interface in order to limit some traffic.This article is about how to test ACL from the router which is not very intuitive for everyone. Below scenario shows simple s…
The Cisco RV042 router is a popular small network interfacing device that is often used as an internet gateway. Network administrators need to get at the management interface to make settings, change passwords, etc. This access is generally done usi…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

872 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question