Add Vlan and subnet

May 11, 2010 at 21:25:43
Specs: Windows 7
I need the command to add a vlan10 and subnet 10.20.30.32/28

Please kindly send me the commands I will need to do this, I am a cisco novice

It is a catalyst 3750 with IOS
thanks.


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#1
May 12, 2010 at 07:18:36
What do you want to add each to?

Adding a VLAN to a port is simple enough, you go into global configuration mode and then add it to the appropriate interface as follows (using fa0/1 as the example):

Switch> enable
Password:
Switch> configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch (config)> int fa0/1
Switch (config-if)> switchport access vlan 10

Is the subnet going to be VLAN 10?


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#2
May 12, 2010 at 10:04:01
Yes, the subnet will be vlan 10 with the IP address of the subnet indicated above, so the command that I really need is the command to add the vlan to that subnet of 10.20.30.32/28 oh and what does the slash 28 mean if you don't mind please?

thank you so much in advance


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#3
May 12, 2010 at 10:45:14
Also when I try to add the subnet IP to route after adding the vlan 10 in question it says it overlaps with already added vlan 8..does that mean I need to figure out another IP subnet to use that that IP subnet is in use..and please forgive me for sounding like an idiot I just wanted to make sure..

thanks again


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#4
May 12, 2010 at 12:21:25
oh and what does the slash 28 mean if you don't mind please?

Ok, that's CIDR notation

You can research that on google yourself.

You don't configure the subnet on the switch. You configure the VLAN, assign it to a port (or ports) and then plug clients into the ports.

All clients plugged in to ports with the same VLAN tag should be in the same subnet or they won't be able to communicate with each other.

You would configure the subnet on a router if you have one in your network somewhere.

To be honest, I don't think you're going to have much luck doing this as you seem to be a little out of your depth with regard to this.

Are you taking a Cisco course and this is an assignment you need help with?



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#5
May 12, 2010 at 13:29:56
Well, I thank you for your response. I need to be able to add the IP to the VLan interface on the switch to be able to route between the VLANS on the switch as I thought the VLAN interfaces must be configured with an IP address. so that when the switch receives a packet destined for another subnet/VLAN, the switch looks at the routing table to determine where to forward the packet. The packet is then passed to the VLAN interface of the destination. so that It is in turn sent to the port where the end device is attached.

And I have IProuting turned on on my switch...also, when I try to add the IP it says "it overlaps another VLAN" now if the statement above is not accurate please let me know and any help will be appreciated to clarify my misinformation.

thanks.


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#6
May 12, 2010 at 14:39:58
I need to be able to add the IP to the VLan interface on the switch to be able to route between the VLANS

I've never tried routing on an L3 switch this way. We use routers, and not Cisco routers either. So I'm afraid I can't be of any help to you with setting up the routing table on your switch.

You'll just have to get on Cisco's website and look up examples of routing on this particular model switch if nobody else who knows how responds.


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#7
May 12, 2010 at 14:53:26
Okay thanks...Is anyone else out there, able to help?? please kindly feel free.

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#8
May 12, 2010 at 14:59:42
You don't know what a CIDR is but you are messing with L3 switches. I highly recommend you get some help with this project before you mess something up. Unless this is just a test Network for school. L3 switches are usually used in WANs not LANs because they are soooo expensive and super fast. We only use L2 Switches wich do not work with IP only ARP in our LAN.

I suggest you read this...

http://www.cisco.com/en/US/tech/tk3...


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#9
May 12, 2010 at 15:11:53
Again, I thank you for your time and information. I will read the suggested article.

Cheers!


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#10
May 12, 2010 at 19:31:21
Cisconovicenlv, if I may, I would like to add a slight correction to your understanding of vlan and subnet traffic. A vlan does not do any routing. Routing is handled at layer 3 whereas vlans are at layer 2 of the osi model.

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#11
May 12, 2010 at 19:57:41
thank you wanderer, I appreciate that. I totally agree. so in other words I would like to connect this vlan to an IP subnet ie: 10.20.30.48/28
do you by chance know the command to accomplish that on a cisco 3750 switch?

thanks in advance


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#12
May 13, 2010 at 07:24:39
ace_omega

L3 switches are usually used in WANs not LANs because they are soooo expensive and super fast. We only use L2 Switches wich do not work with IP only ARP in our LAN.

I would guess this might depend on budget more than anything else. At least, I know of no reason to not use L3 switches throughout your network....if you can afford it.

I'm presently in the middle of evergreening all the old cisco junk out of our network and replacing it with L3 switches. Which granted aren't cheap at $5,000.00 each.

Out of the 15 closets in our main center, I have 4 closets left to replace but those will have to be put on hold for a little while due to budgetary constraints thanks to the economy.


Cisconovicenly

I would like to connect this vlan to an IP subnet ie: 10.20.30.48/28
do you by chance know the command to accomplish that on a cisco 3750 switch?

You're still not getting it. You don't "connect" a subnet to a VLAN. At least, not in the sense you're thinking.

Let's say I have a switch with 4 VLAN's configured on it. I have 4 blocks of 12 ports set to, one block to each VLAN:

VLAN 1 - Ports 1-12
VLAN 2 - Ports 13 -24
VLAN 3 - Ports 25 - 36
VLAN 4 - Ports 37 - 48

Now, I have two computers configured with the following IP addresses:
PC1 = 192.168.0.1
PC2 = 192.168.0.2

I plug them in to the first bank (VLAN 1) and start a continuous ping between them.

I can then move their plugs into any ports in the VLAN 2 bank and they will continue pinging.

I can then move their plugs into any ports in the VLAN 3 bank and they will continue pinging....and so on to bank 4

If I plug one into the VLAN 1 bank and the other into the VLAN 2 bank, they stop communicating because they're now plugged into ports that are configured for different VLAN's.


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#13
May 13, 2010 at 08:06:59
I wasn't saying it was not possible just that it was impractical in a LAN environment because a L2 device with routers are usually fast enough and way cheaper. I wouldn't even consider a L3 switch unless I am dealing 10000 nodes or more. You must have a very big LAN maybe even a MAN to be using L3 switches.

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#14
May 13, 2010 at 10:16:05
Well, we have sites in 4 different cities.

Our main location has 15 closets with multiple switches in each (anywhere from 2 to 4 - not including our data center) and we have two other physical locations within this site and one of our other sites has two locations as well.

So that's two MAN's and one big WAN.

So yes, we have a pretty large environment.

I wasn't trying to say it wasn't possible, I was suggesting for the most part, it would be a budgetary constraint. The only real difference between and L2 and an L3 switch is the ability to route.

If you have a small environment and don't want to spend $$ on a separate router, an L3 switch would be the optimum way to go since it can also route. To my way of thinking, the larger the environment, the less likely you are to need L3 switches in your closets since you should have a router, or routers, in your network to handle all routing.

To be completely honest, we didn't purchase these switches based on them being L3. Between our multiple UNIX (OpenBSD) based routers/firewalls, and the fact that we use our dual redundant Core switches to route client subnets (the UNIX based routers provide segmentation between different parts of our LAN and separation/protection from the Internet), it's absolutely not important that the switches in the closets are L3 as we don't need, or use, that feature.

The main reason for the choice we made is that the switches are the same brand as our Core switches, they're high density (ie: 48 port), they cascade together beautifully (we have several 5 switch stacks in our date center that are for all intents and purposes a single large switch because they've been cascaded) and their interoperability with each other is excellent, they offer 1,000 Mbps to the desktop and have 1,000 Mbps fibre uplink ports. (We recently upgraded the backplane of our core switches to 10,000 Mbps) There are a lot of other features to these switches as well that made us go with this brand.



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