DHCP Relay Agent and Static Routes


1) I have a lab which consists the following machines:
- DC1 [Windows 2003 server; Domain Controller for "Boba" Domain; it is located at LAN 1(; the ip address is; it is DHCP Server; also DNS server; The Scope for DHCP is for the LAN 2 ( to]
- DC2 [Windows 2003 server; Replica Domain Controller for "Boba" Domain' it is located also at  LAN 1; the ip address is]
- RRAS1 [Windows 2003 server; Routing and Remote Access Server; There are 2 NICS; The first NIC's ip address: (at the LAN 1); the 2nd NIC's ip address:; The Routing and Remote Access is enabled at this server; the DHCP Relay Agent is also enabled for the LAN 2 (IP of to and the Router's IP address is]
- XP1 [It is supposed to be located at LAN 2]
2) All these machines (DC1, DC2, RRAS1 and XP1) are connected to the HUB (I believe this is NOT the proper Hardware Topology; and maybe this is the cause of my problem)
3)After I enabled the DHCP Relay Agent,
- I checked at DHCP server at "the address leases": the ip address for XP1 (
- But when i go to XP1 (i do ipconfig/release and ipconfig/renew), i can not get the IP at all (the ip is always
4)To compensate the DHCP Relay Agent, i create 2 static routes: LAN 1 to LAN 2 and LAN 2 to LAN 1,
- But the result is still the same: i can not renew the ip address of XP1; it is always
5)But i can create static IP address to XP1; i gave the IP addess of to the XP1, and it works well:
-Xp1 can ping DC1, DC2, etc
-XP1 can join the "Boba" Domain
6)Before i did # 5, i tried to do the RESERVATION at DHCP server by putting in the MAC address of XP1, but still did not work; The XP1 still get's IP address
7) This is not good; there must be "Topology's problem"
-maybe i need the Router, or what ..... i am not sure
8) My Questions:  I have a Router (which i have never used); Router Cisco 1720 (i believe there is IOS image in it); i) Could somebody PROPOSE me which HARDWAREs that i should have to make this small networking functioning, ii) Could you sketch the "lay out" or topology for it?, iii) Other things that you think are necessary to make this lab working
9) Thank you

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What kind of "hub" is this?
you must have a router in order to have communications between LANs.
make sure you have the correct VLAN IP address in the DHCP scope
If it is a Layer 3 switch, that is really all you need in order to get it going.
If it is a manageable Layer 2 switch capable of multiple VLANs, then you would have to assign the ports to the respective VLANs and create a trunk link to the router.
If it is a dumb switch/hub, you will have to have 2 links to the router (1 for each VLAN), assign the VLAN IP on each interface for the router and make those VLAN IPs the default gateways for the devices.
The fact that you created a DHCP helper address leads me to believe that it is a manageable Layer 2 switch, or a Layer 3 switch.
Post the model of the switch and the config you entered.
tjieAuthor Commented:
1) The Switch/Hub
-Name: Farallon (Starlet/8)

2) DHCP Relay Agent (DHCP helper)
-Routing and Remote Access > RRAS1(local) > IP Routing > DHCP Relay Agent
-When i highlight "DHCP Relay Agent" (on the left Side of the console), i will see "Local area connection 2 (LAN 2)" on the right side of the console
-Also, When i highlight "DHCP Relay Agent", right-click, and select "properties", i can see " and" as the server address

3) Static Routes
-Routing and Remote Access > RRAS1(local) > IP Routing > Static Routes
-When i highlight the "static routes" (on the left side of the console), i can see the followings (on the right side of the console):
Destination     Network mask   Gateway         Interface  LAN 1      LAN 2

4) If you can attach the "Sketch" per based on your recommendation of the "topology" of this network (Router, switch, etc), and also please recommend me the type and model of  the used Router or switch which i will buy it at ebay

5) Post it back with your further comments please
6) Thank you

sounds like a layer 3 switch which means it should be able to do everything with no more equipment.
I wasnt referring to the DHCP relay conf on the switch. I am saying to make sure that you have 2 DHCP scopes created on the DHCP server and that each should have the proper Router IP in it (scope option 003).

the "router" for scope Vlan 1= Vlap 1 interface IP address on the switch.

the "router" for scope Vlan 2= Vlap 2 interface IP address on the switch.  
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tjieAuthor Commented:
1) I do not think that i need the DHCP Scope for LAN 1 (This LAN 1 is only for server DC1 and DC2; i do not plan to have a client machine in this LAN 1)
2) Yes, of course i have a DHCP Scope for LAN 2 (and also 2 range of Exclusions; i also make the DHCP Backup at DC2)

3) This is possibly a HUB as it does not have a serial port where i can plug in the Rollover Cable; am i right? (This device has only 8 network ports and a switch for power cable and " a switch to put it uplink")

4) Theoretically it should work; but  the fact it does not work; The XP1 client machine can not get the IP address at all from the DHCP server (although i have installed the DHCP Relay Agent, and even 2 static routes); This XP1 client machine can connect to the Boba Domain as i MANUALLY give the Static IP there.

5) Any other ideas?

You still didnt comment on the router option for the dhcp scope. its not simply a matter of making the scope. You also have to state what the relay agents IP address is (on the server as well as the switch).  This means a relay agent on the switch  and the "router" option on the dhcp server (since the clients are on a different VLAN).
no idea if it is a hub or not as I have never dealt with that brand.
tjieAuthor Commented:
" You still didnt comment on the router option for the dhcp scope"
-Scope Option 003:

" You also have to state what the relay agents IP address is (on the server as well as the switch) "

-The Relay Agent is located at RRAS1 machine
- I believe i have explained in detail related to it above
-There are 2 Network adaptors in this machine (The first NIC is for LAN 1; the TCP/IP setting is as the followings: * Ip address:, * The Subnet Mask is, *The Default Gateway is BLANK, * The Primary DNS is, * The Alternate DNS is ( The 2nd NIC is for LAN 2; the TCP/IP setting is as the followings: * Ip address:, * The Subnet Mask is, * The Default Gateway is BLANK, * The primary DNS is, * The Alternate DNS is

- I do not know how to get the IP address of the Relay Agent on the SWITCH as i can not connect to the Switch (It does not have "serial port"; the switch has got the network ports ONLY)

You need a switch that is capable of forwarding a DHCP request. That would be a manageable layer 2 or layer 3 switch.
if using a Layer 2 switch see diagram A.
On that router, you will have to create a dhcp helper address (or relay agent depending on what brand of router you use) for each vlan that needs DHCP.
If using a Layer 3 switch, the config is the same, but you just dont need the trunk link, and instead of sub interfaces, you will have vlan interfaces. (diagram b)


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