DHCP Relay + PPP

[JOBY THAMPAN]

>  
> Hi all,
> 
> 	I did a setup like this, All are Linux machines
> 
> 
> Machine 4
> ____________________________
> |				|
> |	Client Machine		|
> |				|
> |		eth0		|
> |___________________________|
> 		| 
> 		|
> 		|
> Machine 3	|
> 		|192.168.40.1
> _____________ |______________
> |		eth1	          |
> |			          |
> |			          |
> |			          |
> |		ppp0 pppoe-client         
> |__________________________|
> 		    |
> 		    |192.168.30.30
> 		    |
> Machine 2	    |						 
> 		    |192.168.30.1
> ________________|___________		
> |		ppp0		|
> |PPPoE Server         		|
> 
> |_____________Eth1__________	|					
> 		|192.168.10.130
> 
> 		|						
> 		|						
> 		|						
> Machine 1	|192.168.10.1					
> _____________ |______________					
> |		Eth0     		|
> 
> |				|					
> |	DHCP Server     	|					
> |____________________	_______|					
> 	
> 
> 	DHCP Relay agent is running on Machine 3 which listens on both ppp0
> and eth1
> 
> 	DHCP Server is ran on Eth0
> 
> 	When client machine renews the IP it must get an IP in the range
> 192.168.40.X
> 
> 	The working I saw here is when client machine ernwes the IP 
> 	DHCPDISCOVER is travelling to DHCP Server with GIADDR field
> 192.168.40.1
> 
> 	DHCP Server is responding with a DHCP OFFER of 192.168.40.20
> 
> 	But this offer is reaching only upto ppp0 interface of Linux machine
> 3
> 
> 	
> Then I did another setup
> 
> Machine 5
> ____________________________
> |				|
> |				|
> |				|
> |	Client Machine		|
> |				|
> |_______________eth0________ |
> 		   |
> 		   |
> 		   |
> Machine 4	   |
> _______________ |_____________
> |		eth1		|
> |	DHCP Relay Mach	|
> |				|
> |		eth0		|
> |___________________________|
> 		| 
> 		|192.168.40.5
> 		|
> Machine 3	|
> 		|192.168.40.1
> _____________ |______________
> |		eth1	          |
> |			          |
> |			          |
> |			          |
> |		ppp0 pppoe-client         
> |__________________________|
> 		    |
> 		    |192.168.30.30
> 		    |
> Machine 2	    |						 
> 		    |192.168.30.1
> ________________|___________		
> |		ppp0		|
> |PPPoE Server         		|
> 
> |_____________Eth1__________	|					
> 		|192.168.10.130
> 
> 		|						
> 		|						
> 		|						
> Machine 1	|192.168.10.1					
> _____________ |______________					
> |		Eth0     		|
> 
> |				|					
> |	DHCP Server     	|					
> |____________________	_______|		
> 
> 	In this setup when DHCP Relay is ran on another Machine, client
> machine successfully recieved the IP Address 192.168.40.20 from DHCP
> Server.
> 
> 	Can somebody please explain me why DHCP Relay when listened on ppp0
> interface didn't got the packet???
> 
> 	Is it because in the first case DHCP Relay listened on pppo which
> doesn't have a hardware addresss.
> 
> 
> Rgds
> Joby
> 
> 
> 
> 
> 
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