[RESOLVED !!!] Multi Homed DHCP - VLANs, Hosting Remote Subnets - Working With DHCP Relay Agent

Tue Mar 19 15:50:54 UTC 2013

Thanks Glenn Satchell, That's Brilliant. Really good reply with valuable
knowledge and helping community.

Well Done !!

Regards / Prabhpal

> Hi
>
> It's great to see that you have your dhcp working. Now we come to
> optimising the configuration :)
>
> I'll just show two subnets here for the example:
>
>> subnet 192.168.11.0 netmask 255.255.255.0 {
>>  option routers 192.168.11.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.11.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.11.100 192.168.11.200;
>> }
>> subnet 192.168.21.0 netmask 255.255.255.0 {
>>  option routers 192.168.21.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.21.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.21.100 192.168.21.200;
>> }
>
> You can specify common attributes at the global level, and these will be
> inherited by the subnet. Also netmask and broadcast will be derived from
> the subnet statement so they are typically not used. As an example the
> above definitions could be written as:
>
> option domain-name-servers 41.211.0.41;
> option domain-name "teledataict.net";
> default-lease-time 1800;
> max-lease-time 2700;
>
> subnet 192.168.11.0 netmask 255.255.255.0 {
>   option routers 192.168.11.1;
>   range 192.168.11.100 192.168.11.200;
> }
> subnet 192.168.21.0 netmask 255.255.255.0 {
>   option routers 192.168.21.1;
>   range 192.168.21.100 192.168.21.200;
> }
>
> This approach can be useful where you have many subnets. Some sites have
> hundreds or thousands of subnets. You can also override a setting by
> re-defining it inside the subnet if you wish.
>
> regards,
> -glenn
>
> On Tue, March 19, 2013 11:15 pm, Prabhpal S. Mavi wrote:
>> Hi Dear All,
>>
>> We were having requirement where "isc-dhcp-server" have to issue ip
>> address for multiple remote subnets. Since they are remote subnets, my
>> DHCP server it self do not belong (connected) to those subnet either by
>> physical or logical interface (sub interface etc..). Saying other way,
>> NONE of the interface of my DHCP server has direct connectivity to those
>> subnets.
>>
>> Our server belongs following networks using sub interfaces (LANs){
>> 192.168.10.1
>> 192.168.20.1
>> 192.168.30.1
>> 192.168.40.1
>> 192.168.50.1
>> }
>>
>> But business requirement was saying i have to issue ip address for
>> remote
>> subnets as well such as {
>>
>> 192.168.11.0
>> 192.168.21.0
>> 192.168.31.0
>> 192.168.41.0
>> 192.168.51.0
>> }
>>
>> emphasizing, please note, none of the interface of my server is in these
>> networks (11,21,31,41,51), i have to issue these ip address for the
>> remote
>> clients, DHCP request come through a Cisco Router acting as
>> "Relay-Agent"
>> (DHCP Helper) remotely. Saying other way, some remote client will
>> request
>> for the DHCP ip address from my server using Cisco Router configured as
>> "dhcp-helper"
>>
>>
>> STEP 1.) Configure your interface for DHCP to listen
>>
>> INTERFACES="vlan10 vlan20 vlan30 vlan40 vlan50"; - If you are not using
>> VLANs, do the following.
>> INTERFACES="eth1.10 eth1.20 eth1.30 eth1.40 eth1.50";
>>
>> ddns-update-style none;
>> authoritative;
>> log-facility local7;
>>
>> STEP 2.) Empty Subnet Declaration For Configured Interfaces, EMPTY ONLY,
>> if you do not want to issue IP for these networks wehre your DHCP is
>> connected, else declare the pool & options. But i do not want any ip
>> from
>> this range.
>>
>> subnet 192.168.10.0 netmask 255.255.255.0 {
>> }
>> subnet 192.168.20.0 netmask 255.255.255.0 {
>> }
>> subnet 192.168.30.0 netmask 255.255.255.0 {
>> }
>> subnet 192.168.40.0 netmask 255.255.255.0 {
>> }
>> subnet 192.168.50.0 netmask 255.255.255.0 {
>> }
>> subnet 41.211.31.0 netmask 255.255.255.0 {
>> }
>> subnet 172.25.1.0 netmask 255.255.255.252 {
>> }
>>
>> STEP 3.)
>>
>> Subnet Declaration For REMOTE Networks - These clients are far away, my
>> server cannot be the part of these networks. i am going to receive DHCP
>> request from REMOTE Cisco router configured as DHCP-helper.
>>
>> subnet 192.168.11.0 netmask 255.255.255.0 {
>>  option routers 192.168.11.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.11.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.11.100 192.168.11.200;
>> }
>> subnet 192.168.21.0 netmask 255.255.255.0 {
>>  option routers 192.168.21.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.21.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.21.100 192.168.21.200;
>> }
>> subnet 192.168.31.0 netmask 255.255.255.0 {
>>  option routers 192.168.31.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.31.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.31.100 192.168.31.200;
>> }
>> subnet 192.168.41.0 netmask 255.255.255.0 {
>>  option routers 192.168.41.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.41.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.41.100 192.168.41.200;
>> }
>> subnet 192.168.51.0 netmask 255.255.255.0 {
>>  option routers 192.168.51.1;
>>  option subnet-mask 255.255.255.0;
>>  option broadcast-address 192.168.51.255;
>>  option domain-name-servers 41.211.0.41;
>>  option domain-name "teledataict.net";
>>  default-lease-time 1800;
>>  max-lease-time 2700;
>>  range 192.168.51.100 192.168.51.200;
>> }
>>
>>
>> STEP 4.) restart dhcp daemon | check logs | Testing
>>
>> Note: This config is copy & past from working server.
>>
>> Grate Thanks to Simon Hobson
>> Grate Thanks to Christian Kratzer
>>
>>
>> Thanks / Regards
>>
>>
>>
>>
>>
>> _______________________________________________
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>> dhcp-users at lists.isc.org
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>
>
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