Two DHCP ranges in one DHCP server using one NIC on a MPLS network

pablobhz · 02-28-2013, 11:11 AM

Hello boys.

I've searched around the forum and got some clues about what i'm doing - but i'm still not having any success.

As my topic's title describes, i want to serve dhcp for two networks - connected trough an MPLS link using only one NIC.

They're on the same subnet (255.255.255.) and only the range is different(network A is 192.168.1.0 , network B 192.168.2.).

I think i've built my dhcpd.conf right but the other network (192.168.2.0) can't get any ip address. I'm on the network 192.168.1.0 and i can get ip from my dhcp server without problems.

I'm posting my dhcpd.conf here - if anyone finds out there's something wrong just tell me.
Thanks in advance

Pablo

***
dhcpd.conf
***

Code:

deny-unknown-clients;
ddns-update-style interim;
default-lease-time 86400;
max-lease-time 345600;

        subnet 192.168.3.0 netmask 255.255.255.0{} 
# Pharmascience Betim e SJL
shared-network Pharmascience {

        ###################################
        #Range Pharmascience - Betim      #
        ###################################
        subnet 192.168.1.0 netmask 255.255.255.0{

        range  192.168.1.1 192.168.1.254;
        option routers 192.168.1.238;
        option domain-name "pharma-bet.intranet";
        option ip-forwarding off;
        option broadcast-address 192.168.1.255;
        option subnet-mask 255.255.255.0;
        option ntp-servers 192.168.1.247;
        option domain-name-servers 192.168.1.253;
        option domain-name-servers 192.168.1.254;

                host TI002 {
                hardware ethernet 00:1C:C0:6E:2E:13;
               fixed-address 192.168.1.236;
                        }
                                                }


        ###################################
        #Range Pharmascience -  SJL       #
        ###################################

        subnet 192.168.2.0 netmask 255.255.255.0{

        range  192.168.2.1 192.168.2.254;
        option routers 192.168.2.254;
        option domain-name "pharma-sjl.intranet";
        option ip-forwarding off;
        option broadcast-address 192.168.2.255;
        option subnet-mask 255.255.255.0;
        option ntp-servers 192.168.1.247;
        option domain-name-servers 192.168.2.253;

                host TI005 {
             hardware ethernet 00:1B:11:04:BC:56;
             fixed-address 192.168.2.210;
                        }
                                                }
                }

Those two fixed hosts are for testing purposes - each one is on a network.

TJNII · 02-28-2013, 08:16 PM

Does Linux see the subnets as separate at L2? So when it receives a broadcast packet it knows which vlan (or equivalent for MPLS - never used that) the packet came from?

Please post the output of "ifconfig -a"

pablobhz · 03-01-2013, 04:49 AM

There it goes

Code:

[root@icebird dhcp]# ifconfig -a
em1       Link encap:Ethernet  HWaddr D4:AE:52:85:14:BC
          inet addr:192.168.1.247  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::d6ae:52ff:fe85:14bc/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:84532101 errors:0 dropped:0 overruns:0 frame:0
          TX packets:84246302 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:54587451244 (50.8 GiB)  TX bytes:70359471322 (65.5 GiB)
          Interrupt:36 Memory:da000000-da012800

em2       Link encap:Ethernet  HWaddr D4:AE:52:85:14:BD
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:48 Memory:dc000000-dc012800

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:38737 errors:0 dropped:0 overruns:0 frame:0
          TX packets:38737 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:5117589 (4.8 MiB)  TX bytes:5117589 (4.8 MiB)

Also, i'm posting a part of dhcp log on /var/log/messages

Code:

Mar  1 07:45:11 localhost dhcpd: Internet Systems Consortium DHCP Server 4.1.1-P1
Mar  1 07:45:11 localhost dhcpd: Copyright 2004-2010 Internet Systems Consortium.
Mar  1 07:45:11 localhost dhcpd: All rights reserved.
Mar  1 07:45:11 localhost dhcpd: For info, please visit https://www.isc.org/software/dhcp/
Mar  1 07:45:11 localhost dhcpd: WARNING: Host declarations are global.  They are not limited to the scope you declared them in.
Mar  1 07:45:11 localhost dhcpd: Not searching LDAP since ldap-server, ldap-port and ldap-base-dn were not specified in the config file
Mar  1 07:45:11 localhost dhcpd: Wrote 0 deleted host decls to leases file.
Mar  1 07:45:11 localhost dhcpd: Wrote 0 new dynamic host decls to leases file.
Mar  1 07:45:11 localhost dhcpd: Wrote 0 leases to leases file.
Mar  1 07:45:11 localhost dhcpd: Listening on LPF/em1/d4:ae:52:85:14:bc/Pharmascience
Mar  1 07:45:11 localhost dhcpd: Sending on   LPF/em1/d4:ae:52:85:14:bc/Pharmascience
Mar  1 07:45:11 localhost dhcpd: Sending on   Socket/fallback/fallback-net
Mar  1 07:45:29 localhost dhcpd: Unable to add forward map from ASR011.pharma-bet.intranet to 192.168.1.11: timed out
Mar  1 07:45:29 localhost dhcpd: DHCPREQUEST for 192.168.1.11 from 78:2b:cb:c3:44:65 via em1
Mar  1 07:45:29 localhost dhcpd: DHCPACK on 192.168.1.11 to 78:2b:cb:c3:44:65 (ASR011) via em1
Mar  1 07:45:35 localhost dhcpd: DHCPINFORM from 192.168.1.11 via em1: not authoritative for subnet 192.168.1.0
Mar  1 07:45:35 localhost dhcpd: If this DHCP server is authoritative for that subnet,
Mar  1 07:45:35 localhost dhcpd: please write an `authoritative;' directive either in the
Mar  1 07:45:35 localhost dhcpd: subnet declaration or in some scope that encloses the
Mar  1 07:45:35 localhost dhcpd: subnet declaration - for example, write it at the top
Mar  1 07:45:35 localhost dhcpd: of the dhcpd.conf file.

Also, i didn't understood your question man.
I dont think linux see those networks as separates ones - since there is only one connected interface.

leigh8904 · 03-01-2013, 05:10 AM

The first question: how are dhcp requests getting to your host (in 192.168.1.0 network) from 192.168.2.0 network? You need to configure a router to forward them, and include the router's IP address. See "Using a Single DHCP Server to Serve Multiple Networks" at: http://www.linuxhomenetworking.com/w...he_DHCP_Server for some more details.

pablobhz · 03-01-2013, 05:21 AM

Allright - i think i got it.
Only one question

Do i need another DHCP server on the other network or the ip-helper will only forward and clients there will listen ?

Thanks in advance !

pablobhz · 03-01-2013, 07:39 AM

My current scenario is:

Local -> Microtik router -> MPLS LINK <- Microtik Router <- Another Network

Wich one has to be the ip helper ?

leigh8904 · 03-01-2013, 04:40 PM

Quote:

Originally Posted by pablobhz

My current scenario is:

Local -> Microtik router -> MPLS LINK <- Microtik Router <- Another Network

Wich one has to be the ip helper ?

I think the router connected to "Another Network" (assuming DHCP server is connected to Local network).

Also, I don't think the shared-network configuration in your dhcpd.conf is appropriate, as shared-network applies to "physical networks on which more than one IP subnet operates"; see man dhcpd.conf for more details. Am I correct in assuming you have 2 physical networks?

Disclaimer: I am no expert in this area.

Suncoast · 03-04-2013, 04:22 PM

Quote:

Originally Posted by pablobhz

Allright - i think i got it.
Only one question

Do i need another DHCP server on the other network or the ip-helper will only forward and clients there will listen ?

Thanks in advance !

Just passing through today...
Yes, you need some device on the remote network to either be the DHCP server or you need a DHCP relay agent, which is less common thus typically more complicated. The WAN link (normally) does not transmit DHCP discover packets, so these packets will never reach your current server. Not familiar with Microtik routers, but the one on the remote end might have a DHCP ability.

And your EM2 interface is not appropriate for your configuration and should be shut. Seeing zero packets on a single virtual interface/sub interface when others are showing activity is usually a good sign an interface is not properly configured.