1841 and IP Addressing

rkovelman · ‎11-01-2011

Hello,

I have an 1841 and started to run into an issue which can be resolved but looking to see what you guys prefer to do in this situation. We allow users to connect the laptop via ethernet and wireless to our network at the same time as well as an iPad or any other wireless technology. With that said, for the most part each user has two IP's at any given point. The issue comes in is that I have a large amount of IP exclusions for servers, printers, switches, etc on the exclude list. I am starting to see that the 255 address are not enough to make a long story short. I am also using the 1841 to handle another range for the voice network, which has no isues.

What is the best way to fix this issue? Can I run a virtual VLAN off that 1841 for everyone to use and then have the servers, switches, printers, etc on another one? I want to assume no, as both interfaces are used on the back of the 1841 for the two VLANS running now. Or is the only way to handle this with this device to say that as a policy you can only connect assigned company hardware to the network?

Thank You for whatever advice you give.

Reza Sharifi · ‎11-01-2011

Hi,

Assuming you users are connected to a or 2 or 3 switches and the switches are connected to your 1841 router. You can create a new vlan on one of the switches and add the vlan to the trunk that connects to your router and create a sub-interface on the router for that vlan. If you can provide a diagram of the network, it makes it easier to help you.

HTH

rkovelman · ‎11-02-2011

Reza,

Thanks for the responce. I assume you mean a level 2 or 3 switch correct? If so yes, they are all HP's some are 3Coms although same company now. As of now all switches connect to one another either over fibre or Cat5, and the 1841 is plugged into one of the switches with that being the router for all computers. Does this help?

Reza Sharifi · ‎11-02-2011

Hi,

Ok, so the default gateway for your users is the router. You can create a new vlan an one of the switches (where your uses are located) and add a sub-interface to one of the exiting physical interfaces on the router.

so, you need a new vlan and a new ip segment

example:

vlan 100

ip adress 10.10.10.1/24

HTH

rkovelman · ‎11-02-2011

Do I have to add this to all switches or just a one? Can you provide more detail of the programming of the 1841 or that is it, VLAN, address range? I would assume I would make that the priority? Would the 1841 make sure that the VLAN would talk to the other VLANS?

Reza Sharifi · ‎11-02-2011

You need to add this new vlan to the switch where the users are sitting. You can optionally add it to all switches and that would be fine too. I don't know how to configure 3com and HP switches. As for your 1841, find out what interface from which switch is connected to the 1841. And on the 1841 what interface is being used to connect to the switch.

let say on the 1841 the interface is fe0/1 and you have configured vlan 100 an all your switches

interface fastethernet 0/1.100 encapsulation dot1q 100 ip address 192.168.100.1 255.255.255.0

remember if this interface is currently in production , you need an outage window to modify the interface, because it will cause outage unless the inteface has other sub-interface configured on it.

HTH

rkovelman · ‎11-02-2011

Correct as I do no have one:

interface FastEthernet0/0

description Data Network

ip address 192.168.xxx.xxxx 255.255.255.0

speed 100

full-duplex

no mop enabled

!

interface FastEthernet0/1

description Voice Network

ip address 192.168.xxxx.x 255.255.255.0

speed 100

full-duplex

As you mentioned I would need to run this:

interface fastethernet 0/1.100

encapsulation dot1q 100

ip address 192.168.100.1 255.255.255.0

For both the existing and the new vlan, correct?

Reza Sharifi · ‎11-02-2011

Correct, to do this you need to remove the ip address on the main interface and assign it to a sub-interface. since I do not know the last 2 acted and the voice vlan since you x them out I assumed 200, but use what ever vlan id for voice you are using

so:

interface fastethernet 0/1

no ip address

existing

interface FastEthernet0/1.200

description Voice Network

encapsulation dot1q 200

ip address 192.168.200.1 255.255.255.0

speed 100

full-duplex

new

interface fastethernet 0/1.100

encapsulation dot1q 100

ip address 192.168.100.1 255.255.255.0

HTH

rkovelman · ‎11-02-2011

Thank you!

Just to go one step further it would be:

new

interface fastethernet 0/1.100

encapsulation dot1q 100

ip address 192.168.100.1 255.255.255.0

interface fastethernet 0/2.100

encapsulation dot1q 100

ip address 192.168.300.1 255.255.255.0

Now I do have this in there as well:

ip default-network 192.168.100.0

Since the 100 I am going to use for the backbone / infastructure, I assume I should change that to be

ip default-network 192.168.300.0

Correct?