DHCPD , dhcp relays on a large network

[Alexandru Coseru]

The ideea is that   each switch has a subnet  attached to it..

On the backbone   , I have the dhcpd server..

The dhcpd server is not directly attached to the subnets , it has to go 
through a layer3 route to reach them..


                 10.1.1.0/24                                 192.168.1.0/24
srv1     ----------------     L3 SW  A     -------------------------  
subnet1


The L3 SW A  has  DHCPD relay options enabled  ,  so the DHCPD requests 
arrives   on  srv1.
But srv1  has no knowledge  of  class 192.168.1.0/24  , and the server 
cannot be started  (Error:   No subnet declaration for 192.168.1.0/24).
The server has only one ethernet NIC , with ip 10.1.1.1  on it..

Can you elaborate more on shared networks ?


Regards
    Alex


----- Original Message ----- 
From: "Randy Grimshaw" <rgrimsha at syr.edu>
To: <dhcp-users at isc.org>
Sent: Friday, November 10, 2006 5:29 AM
Subject: Re: DHCPD , dhcp relays on a large network


> alexandru:
>   In your example the dhcp server does not need to be aware of the
> vlans - that is being handled by your switches. Because they are acting
> as bootp helpers right? It sounds like you need to review your
> configuration for subnets. I suspect you may have more shared nets than
> you realize.
> <><Randy
>
>
>
> <><Randall Grimshaw
> Room 203 Machinery Hall
> Syracuse University
> Syracuse, NY   13244
> 315-443-5779
> rgrimsha at syr.edu
>>>> alexandru.coseru at totaltelecom.ro 11/09/06 5:55 PM >>>
> Content-Type: text/plain;
> charset="iso-8859-1"
> Content-Transfer-Encoding: quoted-printable
> Hello..
>
> I have a large network  with a couple of subnets and i want to configure
> =
> a DHCPD server  to lease IP addresses  to clients , connected through =
> layer3 switches with relay agents on them.
>
>
> Attached  is a small representation  (no of l3 switches reduced , to =
> make it easier to understand).
>
>
> On each switch I have some subnets , each one assigned to a specific =
> VLAN.
> Between switches , I'm running OSPF  , linked with quagga on srv1   =
> (configured as ASBR) , which is also an internet router  (running bgpd =
> with several ISPs).
>
>
> Srv1:   has ip address 10.1.1.1 on VLAN 2.        The switches have IP =
> 10.1.1.x  , on VLAN 2 also...   This VLAN is used for management and =
> OSPF..
> Each switch has an VLAN2 address  and a specific VLAN assigned to the =
> clients subnet.      VLAN10,VLAN11 , VLAN12 , etc....
>
>
> When I'm trying to declare all subnets in dhcpd.conf , i have the =
> following error:    No subnet declaration for xxxxx.
>
> I cannot define aliases on the srv1 , cause it will break the internet =
> routing...
>
> What should I do ?
>
> a) Install an separate server for DHCPD  and define eth0:1   =
> 192.168.1.1/24 eth0:2 192.168.2.1/24 , etc  on it ?
> b) Declare a subnet of  192.168.0.0/ 255.255.0.0  in dhcpd.conf ?
>
>
> Thanks
>    Alex
>
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