lan network, 1 dhcp, 2 vLAN's

Answered Question
Feb 19th, 2009

i have designed a small network (school project). Check the attachment for the packettracer screenshot.

situation: i have to divide the Personel from the Students with VLAN. so i made a vlan 10 on the main switch for the students, and connect another switch to that port (vlan 10). the dhcp server is also connected to the main switch, now is it possible to use 1 dhcp server for both vlans? (default 1 (personel) and the students, 10). what kind of configuration do i have to make in my router and switch ?

http://img214.imageshack.us/img214/7007/naamloosyq8.jpg

I have this problem too.
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Yes - all you need is:-

1) 1 Layer 3 interface in VLAN 1

2) 1 layer 3 interface in VLAN 10

3) In the VLAN interface for VLAN 10 configure "ip helper-address x.x.x.x" x.x.x.x - IP address of dhcp server

IN the DHCP server you must have 2 scopes configured - 1 scope for VLAN 1 IP subnet and the other scope for VLAN 10 IP subnet.

HTH>

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Correct Answer

Yes - all you need is:-

1) 1 Layer 3 interface in VLAN 1

2) 1 layer 3 interface in VLAN 10

3) In the VLAN interface for VLAN 10 configure "ip helper-address x.x.x.x" x.x.x.x - IP address of dhcp server

IN the DHCP server you must have 2 scopes configured - 1 scope for VLAN 1 IP subnet and the other scope for VLAN 10 IP subnet.

HTH>

datakommunikation Thu, 02/19/2009 - 02:46

ok, packet tracer has no multiple dhcp scope option, but i can also configure the multiple scopes in win2k3 server i guess.. that should work

I am not 100% familular with packet tracer - I guess if you configure a ip helper address to the dhcp server on vlan 10, in capture mode you should see the DHCP request be forwared on to the dhcp server.

In 03 server you have have over 100+ dhcp scopes so you will have no issues.

You can also use the switch as a dhcp server.

HTH>

I am not 100% familular with packet tracer - I guess if you configure a ip helper address to the dhcp server on vlan 10, in capture mode you should see the DHCP request be forwared on to the dhcp server.

In 03 server you have have over 100+ dhcp scopes so you will have no issues.

You can also use the switch as a dhcp server.

HTH>

Jeffrey-T Thu, 02/19/2009 - 03:30

You're putting it wrong.

This is the situation:

We have an setup which have 2 vlan's. Vlan 50 is for the employees and vlan 60 for the students.

The two groups are connected to 3 switches. The first one is connected to the router, server, switch, workstations and employees.

The second switch which is connected on the first switch is connected to the third switch and both of the switches having 40 network components, which are workstations and printers.

Before we configured the vlan, we could ping from a workstation from the students to a workstation from the employees and the network components got their ip addresses.

Now that we have configured the vlan, we cant ping anymore and the network components dont get an ip address.

The ip address of the router is: 192.168.2.1

The ip address of the server is: 192.168.2.2

The start ip address is: 192.168.2.10

I hope that you can do something with this information.

Jeffrey,

VLAN to VLAN traffic MUST BE ROUTED THRU A LAYER 3 INTERFACE.

If your router is the ONLY routing device in the network - then the router MUST have an interface in each of the VLANS.

router int fa 0/0

des ** vlan x**

ip address x.x.x.x

router int fa 0/1

des *vlan y**

ip address y.y.y.y

ONLY then will the traffic from vlan x be routed to VLAN y.

if you do not have a router with 2 interfaces - then you must turn it's only interface into a trunk and use dot1q trunking.

see the below config example:-

http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a00800949fd.shtml

HTH>

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