DHCP & BOOTP design problem

I'd like to sollicite the good knowledge of AOs.

My problem:
I'd like to assign IP address basing on the interface on which the the client request is coming to the router. I can't think that's not achievable but does anyone confirm?
This may be a very simple issue for some of ya; please help! :(

I quickly read the RFC951 but I can't find an answer.

Details:
The network is basically composed by a switch, a router & a DHCP server as follow:

Code:

------------- | Router |___________DHCP Server ------------- | | 802.1q trunk | ___________________ | Switch | | ______ ______ | | |VLAN1| |VLAN2| | | ----------- ---------- | -------------------------------- | [ host 1 host2

With 802.1q logical/virtual interface the router sees 2 bridge-group & subnets.
The router performs bootp to mediate DHCP request to the server.
The router may be CISCO or Linux or whatever that's an open issue.

My goal is to configure the IP of "host 1" into the associated VLAN subnet just using the fact that BootP knows on which logical port it receives the request!

ouf!

Thanx to guys that have been through all of this!

Well if your running 802.1q then you should be able to set up multiple sub interfaces on your router for each VLAN on the switch. That way each VLAN basically has it's own DHCP segment

Example Config:
ROUTER

interface FastEthernet3/0
no ip address
speed 100
full-duplex
!
interface FastEthernet3/0.1
description Wireless_and_MGMT
encapsulation dot1Q 1 native
ip address 10.0.30.252 255.255.255.0
ip helper-address 10.0.30.245
ip helper-address 10.0.60.244
no ip redirects
standby 1 ip 10.0.30.254
standby 1 priority 110
standby 1 preempt
!
interface FastEthernet3/0.400
description 3rd Floor
encapsulation dot1Q 400
ip address 10.0.29.252 255.255.255.0
ip helper-address 10.0.30.245
ip helper-address 10.0.60.244
no ip redirects
ip pim sparse-mode
standby 2 ip 10.0.29.254
standby 2 priority 110
standby 2 preempt
!
interface FastEthernet3/0.401
description Secondary_Building_LAN
encapsulation dot1Q 401
ip address 192.168.0.41 255.255.255.252
no ip redirects
!
interface FastEthernet3/0.402
description 1st Floor
ip address 10.0.27.252 255.255.255.0
ip helper-address 10.0.30.245
ip helper-address 10.0.60.244
no ip redirects
standby 3 ip 10.0.27.254
standby 3 priority 110
standby 3 preempt
!
interface FastEthernet3/0.403
description 2nd Floor
encapsulation dot1Q 403
ip address 10.0.28.252 255.255.255.0
ip helper-address 10.0.30.245
ip helper-address 10.0.60.244
no ip redirects
standby 4 ip 10.0.28.254
standby 4 priority 110
standby 4 preempt

SWITCH CONFIG
set vlan 1 name default type ethernet mtu 1500 said 100001 state active
set vlan 400 name Dallas_Wired_Users-10.0.29 type ethernet mtu 1500 said 100400 state active
set vlan 401 name 302_Street-192.168.0.40 type ethernet mtu 1500 said 100401 state active
set vlan 402 name 302_1st_Floor type ethernet mtu 1500 said 100402 state active
set vlan 403 name 302_2nd_Floor type ethernet mtu 1500 said 100403 state active

If the router is a cisco, you should be able to use an IP helper address, no?

Thanx d0ppelg@nger, but does not the IP helper just redirect DHCPDISCOVER to the remote DHCP Server (IPhelper=BootP=DHCP Relay or whatever?).

The DHCP server decide the assigned host IP. How does he know in which subnet it should allocate the IP.
Let's take an example: Host belongs to your FastEthernet3/0.400 subnet. The router will forward the DHCPDISCOVER to the DHCP thanx to the BOOTP protocol.
During that exchange of BOOTP there must be some info about the subnet the host belons to, isn't it?

The DHCP server will hand out IP Address from the range that the request came from. Example, If a user's system boots up and it's on the 400 VLAN, which is the FastEthernet3/0.400 segment. The DHCP server will see the requst coming from 10.0.29.252. It will then respond with an IP from the 10.0.29 network in it's DHCP table. DHCP handles the requests, you just have to set up the segments on the router and switch, and add the DHCP segments in your DHCP server. It'll be handled automatically.

Quote:

d0ppelg@nger wrote:
The DHCP server will hand out IP Address from the range that the request came from. Example, If a user's system boots up and it's on the 400 VLAN, which is the FastEthernet3/0.400 segment. The DHCP server will see the requst coming from 10.0.29.252. It will then respond with an IP from the 10.0.29 network in it's DHCP table. DHCP handles the requests, you just have to set up the segments on the router and switch, and add the DHCP segments in your DHCP server. It'll be handled automatically.

Of course that's obvious. :idea:
You opened my eyes when I was blind.

Thanx buddy