Cisco VLAN Questions (CCNA Study)

[Phobos1821]

Here are a few questions. Any help would be appreciated. I am studying for my CCNA, and have a few basic questions about VLAN's.

I currently administrate a 70 workstation network with 6 Cisco 2900 series switch, and a 2600 series router in a w2k ad network. I am considering VLAN'ing to segement the network into different broadcast domains, but am running into some difficulty with my studying.

1: If I create multiple VLANs, how would my AD/DHCP Server be a member of multiple VLANs? It is a Compaq DL360G2. How would it know to give IP addresses to different subnets?
2: How can I make a server a member of multiple Vlans? I know I can add the servers switch port to the trunk if it is ISL capable, but how would I program that in the switch, and is the DL360G2 NIC capable of this? Any setup required on the server?
3: Is it easier to create a "Server VLAN", and forward all VLANS to it? If that is the case, how do I setup that VLAN to accept traffic from all other vlans?
4: Our router just connects us to the internet, and it is IP Classless, so how can i configure it to accept traffic from all the vlans? just add secondary ip addresses to the interface so it can become a member of all vlans? and then set the gateway through dhcp so it can access it?

Any help would be appreciated. Thanks for looking.

 

[TimRegester]

With only 70 workstations It would need very levels of broadcast or a valid security argument to justify VLANing this network.

Rule One

Keep it simple. I would suggest that a flat network will probably do you. Just because you can do something is no reason at all to do it.

 

[jdavis1]

I would tend to agree that in general a 70 workstation network would not need to be subnetted unless you have a very high level of broadcast traffic. In this case I would try to fix the broadcast problem rather than subnet. However, to try and answer some of your questions:

First of all, you need to understand that if you create separate Vlans that it is conceptually identical to creating two separate LANS with different IP subnets. In order to communicate between the Vlans you need a router (your 2600). Your servers don't necessarily need to communicate directly with every Vlan. You put them on one Vlan and clients on other Vlans communicate with it via the router. You can still use the DHCP server to dole out addresses to subnets other than the one the server is on (see router config later).

Some NICs do support trunking (multiple Vlans), but usually not ISL which is Cisco proprietary. It will be IEEE 802.1q trunking. I have never found it necessary to enable this on any server or workstation.

Here is how you would configure a trunk port on your 2600 to carry 3 Vlans. Note that the Vlan number is determined by the "encapsulation" statement, not the subinterface number. I'm using dot1q trunking. I would stick with the standard rather than use the older Cisco proprietary ISL. This configuration assumes that the DHCP server is on Vlan 1. The helper-address statements on Vlans 2 and 3 are there to direct the router to forward DHCP requests on those Vlans to the server (assumed to have an address of 10.1.1.2).

interface FastEthernet0/0
no ip address
speed 100
full-duplex
!
interface FastEthernet0/0.1
description *** Vlan 3
encapsulation dot1Q 1
ip address 10.1.1.1 255.255.255.0
no ip redirects
!
interface FastEthernet0/0.2
description *** Vlan 2
encapsulation dot1Q 2
ip address 10.2.2.2 255.255.255.0
ip helper-address 10.1.1.2
no ip redirects
!
interface FastEthernet0/0.3
description *** Vlan 3
encapsulation dot1Q 3
ip address 10.3.3.3 255.255.255.0
ip helper-address 10.1.1.2
no ip redirects
!

The switchport that connects to the router would look something like this on a 2900:

interface FastEthernet0/1
description *** Connection to 2600 router
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1-3,1002-1005
switchport mode trunk
spanning-tree portfast
!

Hope this helps