RE: checking DHCP (forwarding) from a router interface

From: Geert Nijs (geert.nijs@simac.be)
Date: Tue May 30 2006 - 11:22:08 ART


Petr,
 
That is the point: i want to OBTAIN an ip address, but WITH an ip address configured on the interface.
I need to "emulate" a host.
I do know that without an ip address it will not work (see first "solution").
 
mmmm... just came up with a possible third solution:
 
int fa0/0
 ip address 1.1.1.1
 ip address dhcp secundary
 ip helper-address 10.10.10.10
 no keepalive
 
 
mmm dont think that secundary addresses can be DHCP....
 
Geert

________________________________

From: Petr Lapukhov [mailto:petrsoft@gmail.com]
Sent: Tue 5/30/2006 13:18
To: Geert Nijs
Cc: ccielab@groupstudy.com
Subject: Re: checking DHCP (forwarding) from a router interface

Geert,

I don't quite get it:

you want router to OBTAIN address via DHCP, or to PROVIDE addresses
via DHCP without having an ip address configured at interface?

If latter is the case, you may check

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801d1dfd.html

This may help :)

Also, forwarding DHCP request from no-ip interface wont work. DHCP requires giaddr field
to be filled in, and that value is taken from interface' ip address.

HTH
Petr

2006/5/30, Geert Nijs <geert.nijs@simac.be>:

        Hi group,
        
        I have come to an interesting challenge that i am trying to resolve.
        Suppose i have a remote router connected to a LAN with no physical access and i want to check/verify that the LAN is capable of DHCP-hosts (DHCP should be working). I want to verify this without physically connecting a host to the lan or router (because it is on the other side of the world).
        Does anyone know of any means to do this ?
        
        Tried already the following:
        
        interface Fa0/0
        ip address dhcp
        no keepalive
        ip helper-address 10.10.10.10 <http://10.10.10.10/>
        
        This can never work actually (dhcp forwarding using helper-addresses actually works by attaching the ip address of the source lan. This way
        the DHCP server can determine in which VLAN it has to assign an address....making the LAN itself DHCP we are running in the chicken-egg problem.......mmm...)
        
        Next i tried something like this:
        
        bridge irb
        interface Fa0/0
        bridge-group 1
        ip address dhcp
        no keepalive
        
        interface BVI1
          ip address 1.1.1.1 <http://1.1.1.1/>
          ip helper-address 10.10.10.10 <http://10.10.10.10/>
        exit
        
        I am trying to bridge the DHCP request generated by the router on Fa0/0, back to the BVI interface and then forward it to the DHCP server to get an ip address in the range 1.1.1.x
        But it doesnt seem to work....
        
        Any other ideas ?
        
        regards,
        Geert
        #####################################################################################
        Simac N.V . trades under the commercial name Simac ICT Belgium.
        This e-mail and any attached files are confidential and may be legally privileged.
        If you are not the addressee, any disclosure, reproduction, copying, distribution,
        or other dissemination or use of this communication is strictly prohibited.
        If you have received this transmission in error please notify Simac immediately
        and then delete this e-mail.
        
        Simac has taken all reasonable precautions to avoid virusses in this email.
        Simac does not accept liability for damage by virusses, for the correct and complete
        transmission of the information, nor for any delay or interruption of the transmission,
        nor for damages arising from the use of or reliance on the information.
        
        All e-mail messages addressed to, received or sent by Simac or Simac employees
        are deemed to be professional in nature. Accordingly, the sender or recipient of
        these messages agrees that they may be read by other Simac employees than the official
        recipient or sender in order to ensure the continuity of work-related activities
        and allow supervision thereof.
        #####################################################################################
        
        _______________________________________________________________________
        Subscription information may be found at:
        http://www.groupstudy.com/list/CCIELab.html



This archive was generated by hypermail 2.1.4 : Thu Jun 01 2006 - 06:33:22 ART