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General Chat Thread, VLAN for Dummies? in General; I really feel like I must have missed out somewhere in my life as I have never had to use ...
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    reggiep's Avatar
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    VLAN for Dummies?

    I really feel like I must have missed out somewhere in my life as I have never had to use or set up a VLAN.
    Can anybody point me to some easy documentation on the subject?
    I think I need to pick it up as I'm about to move our system from CC3 to vanilla and by the looks of it this would help!

    Thanks

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    Butuz's Avatar
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    Great thread - I need to do exactly the same never used vlans or been on any courses like that - need to implement vlans in April/May.

    Idiots guides more than welcome!! Particularly with HP Procurve!

    Butuz

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    Theblacksheep's Avatar
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    Butuz.

    If you are keeping CC3, you cant re/build PCs that are in a VLAN without a DC.

    The RM solution is to put a DC in each VLAN, however you probably want all your servers in one VLAN (ours go in the Default_vlan) on the same as switches.

    We have VLANS for servers and switches, admin PCs, Teacher Laptops, minibooks and 7 different vlans for different parts of the school (great for loopbacks).

    I'll be changing this soon with VLANS for printers, it office and various additional VLANS for the VM infrastructure. Not been on a course I just learnt vlans from this site, the various threads that run on it and the switch manuals

    I'd highly recommend reading all the manuals for your core switches (advance traffic guide etc), as most vlans stuff seems to be in Cisco format but the HP manuals give a great amount of info, to be honest pretty much all you need. There are only slight linguistic changes for procurve, but they can be confusing (trunking/tagged ports etc).
    Last edited by Theblacksheep; 21st January 2009 at 12:26 PM.

  4. Thanks to Theblacksheep from:

    Butuz (21st January 2009)

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  6. 2 Thanks to K.C.Leblanc:

    Butuz (21st January 2009), reggiep (21st January 2009)

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    IanT's Avatar
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    How many of you guys use VLANS on your network?

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    Zimmer's Avatar
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    Two years ago we was having major issues with broadcast traffic on our LAN, with over 1300 workstations and (at the time) over 100 3Com switches our network was being killed by unwanted traffic. The entire network was on 10.x.x.x IP addressing.

    We decided to split our network into VLAN's, the idea was to have a VLAN for each buildings floor. We ended up with 14 VLAN's in total, plus the original 10.x.x.x base VLAN which the servers and core kit still live on.

    We used 192.168.x.x IP addressing for the individual VLAN's, each VLAN having its own gateway. The gateway being the networks core switch (3Com 5500G) configured with multiple IP interfaces.

    The original VLAN setup was fairly complex, at the time we had three core switches in different geographical locations so we had to use VLAN trunking between the cores. Now we have only one single core switch so we simply untag the required VLAN on the fibre port needed.

    Now we are looking at the 3Com managed WiFi products and it looks like we are going to have to trunk a new VLAN to specific ports on edge switches around the campus - Oh the joy

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    I'm looking for the same thing. Perhaps if a few techs/managers who have implemented it could let us know some of the pains and gains involved.

    A few things I don't know are:

    How does this work with the LA/RBC supplied WANs? Do we get a seperate range for each network, or do we use NAT? can we subnet our current range to split it up?

    What about DHCP? I know you can use a "relay agent", but how does that work? How does the DHCP server know which pool to allocate the addresses from?

    How have people VLANed their network? By location, type of device, e.g. Printers, wireless, servers, desktops, or another way?

    What about RADIUS and 802.1x? Has anyone implemented that? If so, what are the implications, ect?

    And finally routing. How is the routing setup? Can we secure different VLANs? e.g. limit to internet access only, imaging server only, etc.

    Sorry to just throw loads of questions out like this. I don't expect them to all be answered, but maybe someone could setup a wiki entry for the subject or something.

    Regards,

    David

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    andyrite's Avatar
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    What switches are you running?

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    Zimmer's Avatar
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    As you say, for DHCP we use a relay agent on our core switch. Our core switch is also acting as the 'router' between all the VLAN's (as it is the default gateway for all devices). So our core switch basically has 15 IP addresses, one primary one for the 10.x.x.x network and an additional 14 secondary IP's for all the VLAN's.

    The DHCP relay agent is easy to configure (especially on 3Com hardware), you just point all DHCP requests to a specific IP on your network, that IP being your DHCP server. If your using Windows Servers then just setup scopes for all the different VLAN's you have created.

    We scoped out or VLAN's like this:

    192.168.2.x to 192.168.4.x - Bellis Building Level 1
    192.168.5.x to 192.168.7.x - Bellis Building Level 2

    ..... and so on.

    192.168.2.1 and 192.168.5.1 are VLAN gateways... and so on.
    Last edited by Zimmer; 21st January 2009 at 02:21 PM.

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    Butuz (21st January 2009)

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    Theblacksheep's Avatar
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    with HP switches DHCP is handled by adding ip-helper X.X.X.X (x= ip address of DHCP server) to each vlan

  14. #11
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    I haven't implemented VLANs on our network but we are on the process of doing it. Our first step was to change all our 3Com switches to more manageable switch like Cisco. And that was done this school year. Next year we will be buying a router which will route VLANs. It is in the router that you program the routing of the traffic to its right destinations. For example, if your DHCP server is on VLAN1, then all traffic for DHCP request from any other VLANs will be routed to VLAN1, where the server is. The DHCP broadcast will remain in VLAN1.

    I am not familiar on configuring cisco routers but i would be very glad if anybody can give some info also.

    Regards

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    Butuz's Avatar
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    Thanks for the reply.

    OK the scenario is this. Currently we have two physically seperate networks, a curriculum network and an admin network. The curriculum is in good nick with HP Procurve managed switches, The admin network is a state with a mix of Cisco switches and hubs, some of it is still on 10mbit.

    So what I wanted to do is use the curriculum network to host at least two vlans, one for the curriculum network, one for the admin network. So I can move both networks onto the same physical infrastructure, yet keep them seperate (to comply with LEAs outdated security) using vlans.

    This will kill a few birds with one stone
    1) Curriculum and Admin networks still cant see eachother.
    2) Admin network instantly gets upgraded to Gigiabit managed HP Procurve, for free.
    3) Consolidating reduces the number of physical switches etc, this saving money on upgrades now, and in the future, and also saving electricity.

    Thats what I want to do. Using more than two vlans to segregate traffic on the network even further will be a bonus.

    Butuz

    Quote Originally Posted by Theblacksheep View Post
    Butuz.

    If you are keeping CC3, you cant re/build PCs that are in a VLAN without a DC. .

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    Butuz's Avatar
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    Cheers - downloading and printing now!

    Butuz

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    Quote Originally Posted by Theblacksheep View Post
    Butuz.

    If you are keeping CC3, you cant re/build PCs that are in a VLAN without a DC.

    The RM solution is to put a DC in each VLAN, however you probably want all your servers in one VLAN (ours go in the Default_vlan) on the same as switches.
    Hmm i don't think this is actually true, we are running CC3 here and we have multiple vlans for various areas across the campus and all CC3 servers are in their own seperate VLANs.

    I think there are few things to the hosts file that needs to be changed in order to build stations on CC3 with VLANs but this is fairly simple to do.

    Ash.

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    Thanks for the information on the DHCP relaying. So its setup for each vlan on the router right?

    The main thing I wanted to find out from people is how it works with the LA/RBC WAN.

    We currently have 2 address ranges:
    admin: 172.16.30.0/24
    curriculum: 172.16.112.0/22
    and all our hosts run off that.

    When setting up VLANs, do you request a different subnet for each VLAN or some other way?

    Thanks,

    David



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