DHCP lease for ROAS or SVI interVLAN Routing

jojopramosjojopramos Member Posts: 415
I am managing a small network with 50 users and 50 IP Phones. I have a flat network with a class c subnet. My DHCP server is Microsoft server 2003 leasing 192.168.1.0 network. My question is if I VLAN my network, use ROAS and apply VTP, how can I configure my DHCP server to lease the right IP to my 3 VLANs. example: (192.168.1.0/192.168.2.0/192.168.3.0). Because I already know that I will configure subinterfaces and encapsulates it in the router for the gateway. I am afraid that 192.168.1.0 subnet will be assigned to a 192.168.2.0 host. Please advise.

Comments

  • peanutnogginpeanutnoggin Member Posts: 1,096 ■■■□□□□□□□
    Hi Jojopramos,

    Your problem isn't too difficult. You'll create your DHCP scopes on your W2K3 server as normal. On your subinterfaces on the router, you'll add the "ip helper-address" that points to the DHCP Server's IP. When a DHCP request is received on the subinterface (let's use 192.168.2.1) the router will forward the request as a unicast to the DHCP server. When the DHCP server receives that packet, it will look at the source IP address and assign an IP address in the same range of the source. That's how the DHCP server knows how to assign an IP address to a specific VLAN. HTH.

    -Peanut
    We cannot have a superior democracy with an inferior education system!

    -Mayor Cory Booker
  • jojopramosjojopramos Member Posts: 415
    Hi peanutnoggin, correct me if im wrong but the steps that I should do so that i dont mess with the DHCP leasing should be:

    1. create VLANs (vtpserver), VTPdomain (clients and server) and trunks (802.1q)
    2. connect the switch interface to routers interface (Cisco 1721) and create subinterfaces (router) with the correct vlans gateway, encapsulates and add the ip helper-address.
    3. Then add the new scopes to my DHCP server and activate it.
  • peanutnogginpeanutnoggin Member Posts: 1,096 ■■■□□□□□□□
    Jojo (if you don't mind me calling you jojo),

    There's no real order in which to complete these steps, but if I was doing, this would be the order in which I complete the steps:

    1. I would create the DHCP scope on the server first. This won't hurt anything and your DHCP server will be ready to answer to DHCP requests.

    2. Next I would create my VLANs, establish my VTP domain, and configure my trunks on the switch (no real rhyme or reason why).

    3. Finally I would configure my subinterfaces on my router.

    HTH

    -Peanut
    We cannot have a superior democracy with an inferior education system!

    -Mayor Cory Booker
  • jojopramosjojopramos Member Posts: 415
    thanks peanutnoggin, anyway, everybody that knows me call me jojo.

    I put my DHCP configuration in the last order because I am afraid that those PC's/edge devices who are connected in the default VLAN (VLAN1) will be issued a wrong IP (IP in another subnet). Instead of issuing 192.168.1.0, the PC on VLAN1 could get a wrong IP (192.168.2.0). Is it a rule of thumb that if your gateway is for example on 192.168.1.0, the IP that will lease will only on that range. Another thing is that I want also to define a new IP subnet to our avaya IP Phones. The IP Phone is connected to the HP Procurve switch (because of PoE). And the PC's are connected to the ethernet port of the IP Phone.
  • peanutnogginpeanutnoggin Member Posts: 1,096 ■■■□□□□□□□
    Ahhh... okay. No worries dude. You should be fine. Just be sure to backup all of your configs and schedule some maintenance time (preferably after hours) to configure this. Be sure to draw it out as well. This'll help you see what's going on and come up with an in-depth solution and a step-by-step guide as to what should be done and when. Do you have a lab environment where you can test your configs out first? You should be very, very, careful when implementing technologies as you learn them on a production network until you've been able to test them, test them, and test them again! icon_rolleyes.gif Did I mention you should test your configs before applying them to production?!?! Good luck, you should be fine.

    -Peanut
    We cannot have a superior democracy with an inferior education system!

    -Mayor Cory Booker
  • jojopramosjojopramos Member Posts: 415
    Thanks peanutnoggin. I have a test equipment which includes the router 1721 and a catalyst 2960 switch. I will create 3 sample vlans in the 2960 and try to trunk to the router throgh 802.1q. By the way, another question is that If I opt to connect the router to any of my switch trunk port, should I connect the other interface to the firewall for internet acces to otehr vlan clients?
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