CentOS - Jan 2017 - Centos 7 dhcpd failure to allow a 2nd network over same interal nic

Everyone,

I am trying to set up a second internal network  (192.168.0.0/24) and
have not been able to get dhcp to start when I have the following in my
dhcpd.conf file :

subnet 192.168.0.0 netmask 255.255.255.0 {
        range 192.168.0.110 192.168.0.130;
        option subnet-mask 255.255.255.0;
        option broadcast-address 192.168.0.255;
        option routers 192.168.0.1;
        option domain-name-servers 192.168.0.1;
}

When i remove the above from dhcpd.conf dhcpd works perfectly

I have my internal nic card set with two ip addresses one of which is
192.168.0.1. the other address is my standard internal network address.

I have also set up the domain server to allow access from
192.168.0.0/24, and the firewall allows internal access to the same
subnet.

The error that I get is the following :

Job for dhcpd.service failed because the control process exited with error
code. See "systemctl status dhcpd.service" and "journalctl
-xe" for details.

When I evaluate journalctl -xe the following is obtained :

dhcpd[18763]: Internet Systems Consortium DHCP Server 4.2.5
dhcpd[18763]: Copyright 2004-2013 Internet Systems Consortium.
dhcpd[18763]: All rights reserved.
dhcpd[18763]: For info, please visit https://www.isc.org/software/dhcp/
dhcpd[18763]: Not searching LDAP since ldap-server, ldap-port and
ldap-base-dn were not specified in the config file
dhcpd[18763]: Internet Systems Consortium DHCP Server 4.2.5
dhcpd[18763]: Copyright 2004-2013 Internet Systems Consortium.
dhcpd[18763]: All rights reserved.
dhcpd[18763]: For info, please visit https://www.isc.org/software/dhcp/
dhcpd[18763]: Wrote 0 deleted host decls to leases file.
dhcpd[18763]: Wrote 0 new dynamic host decls to leases file.
dhcpd[18763]: Wrote 2 leases to leases file.
dhcpd[18763]: Interface enp0s29u1u2 matches multiple shared networks
dhcpd[18763]:
dhcpd[18763]: This version of ISC DHCP is based on the release available
dhcpd[18763]: on ftp.isc.org.  Features have been added and other
changes
dhcpd[18763]: have been made to the base software release in order to
make
dhcpd[18763]: it work better with this distribution.
dhcpd[18763]:
dhcpd[18763]: Please report for this software via the CentOS Bugs
Database:
dhcpd[18763]:     http://bugs.centos.org/
dhcpd.service: main process exited, code=exited, status=1/FAILURE
dhcpd[18763]:
systemd[1]: Failed to start DHCPv4 Server Daemon.

When I review the information about dhcpd it appears that it can manage
the ip addresses for two networks on different nic cards, but is there a
problem in having it manage two networks on the same nic card?

Does anyone have any ideas?  Would sure appreciate your help.


Can you be a little clearer in what you're trying to do, as in the end goal
you are trying to reach?

Having dhcp for two different networks on the same physical network is just
not going to work in any sane fashion...

If you want to serve different dhcp pools to different physical networks
then you could do that via vlan and trunking from the switch to the server
or just ip-helper configuration on the router between the network
boundaries.

James,

Sorry about the clarity... I will try again.  The man pages and examples
in Centos 7 demonstrate the ability to have two networks on the same
dhcpd server, but I did not identify specifically identify that any
reference to having both networks on one network card.  So far you are
obviously correct that this can not be done.  

I am trying to use a wireless router as an adjunct to my home network.
I would like to be able to have public network ip addresses assigned
from my dhcpd server that are in a different subnet from other the
machines in my home.  I thought this would be possible but apparently
not.  I could have the wireless router assign separate subnet ip
addresses but, then I would not be able to access the home subnet
machines with my wireless connected laptop.

Is there any way to be able to have two networks work off of one nic
card with dhcpd?

Greg

Everyone,

I am trying to set up a second internal network  (192.168.0.0/24) and
have not been able to get dhcp to start when I have the following in my
dhcpd.conf file :

subnet 192.168.0.0 netmask 255.255.255.0 {
        range 192.168.0.110 192.168.0.130;
        option subnet-mask 255.255.255.0;
        option broadcast-address 192.168.0.255;
        option routers 192.168.0.1;
        option domain-name-servers 192.168.0.1;
}

When i remove the above from dhcpd.conf dhcpd works perfectly

I have my internal nic card set with two ip addresses one of which is
192.168.0.1. the other address is my standard internal network address.

I have also set up the domain server to allow access from
192.168.0.0/24, and the firewall allows internal access to the same
subnet.

The error that I get is the following :

Job for dhcpd.service failed because the control process exited with error
code. See "systemctl status dhcpd.service" and "journalctl
-xe" for details.

When I evaluate journalctl -xe the following is obtained :

dhcpd[18763]: Internet Systems Consortium DHCP Server 4.2.5
dhcpd[18763]: Copyright 2004-2013 Internet Systems Consortium.
dhcpd[18763]: All rights reserved.
dhcpd[18763]: For info, please visit https://www.isc.org/software/dhcp/
dhcpd[18763]: Not searching LDAP since ldap-server, ldap-port and
ldap-base-dn were not specified in the config file
dhcpd[18763]: Internet Systems Consortium DHCP Server 4.2.5
dhcpd[18763]: Copyright 2004-2013 Internet Systems Consortium.
dhcpd[18763]: All rights reserved.
dhcpd[18763]: For info, please visit https://www.isc.org/software/dhcp/
dhcpd[18763]: Wrote 0 deleted host decls to leases file.
dhcpd[18763]: Wrote 0 new dynamic host decls to leases file.
dhcpd[18763]: Wrote 2 leases to leases file.
dhcpd[18763]: Interface enp0s29u1u2 matches multiple shared networks
dhcpd[18763]:
dhcpd[18763]: This version of ISC DHCP is based on the release available
dhcpd[18763]: on ftp.isc.org.  Features have been added and other
changes
dhcpd[18763]: have been made to the base software release in order to
make
dhcpd[18763]: it work better with this distribution.
dhcpd[18763]:
dhcpd[18763]: Please report for this software via the CentOS Bugs
Database:
dhcpd[18763]:     http://bugs.centos.org/
dhcpd.service: main process exited, code=exited, status=1/FAILURE
dhcpd[18763]:
systemd[1]: Failed to start DHCPv4 Server Daemon.

When I review the information about dhcpd it appears that it can manage
the ip addresses for two networks on different nic cards, but is there a
problem in having it manage two networks on the same nic card?

Does anyone have any ideas?  Would sure appreciate your help.


Can you be a little clearer in what you're trying to do, as in the end goal
you are trying to reach?

Having dhcp for two different networks on the same physical network is just
not going to work in any sane fashion...

If you want to serve different dhcp pools to different physical networks
then you could do that via vlan and trunking from the switch to the server
or just ip-helper configuration on the router between the network
boundaries.

James,

Sorry about the clarity... I will try again.  The man pages and examples
in Centos 7 demonstrate the ability to have two networks on the same
dhcpd server, but I did not identify specifically identify that any
reference to having both networks on one network card.  So far you are
obviously correct that this can not be done.  

I am trying to use a wireless router as an adjunct to my home network.
I would like to be able to have public network ip addresses assigned
from my dhcpd server that are in a different subnet from other the
machines in my home.  I thought this would be possible but apparently
not.  I could have the wireless router assign separate subnet ip
addresses but, then I would not be able to access the home subnet
machines with my wireless connected laptop.

Is there any way to be able to have two networks work off of one nic
card with dhcpd?

Greg
======================================================================
I have not been able to make any headway resolving this problem;
Finally decided to file a bug report on this that I hope is more clear
than the above description :

https://bugs.centos.org/view.php?id=12658

Greg


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> I have not been able to make any headway resolving this problem; 
Personally, I don't understand how you expect the DHCP server to decide
which scope to use when a new connection appears on the network.

DHCP discovery queries are presented from 0.0.0.0 to 255.255.255.255, not to
a particular network's broadcast address.

I'd be interested to see what happens when one of your 10.x.x.x nodes
reaches half time or lease expiration and tries to renew its IP.  I tend to
think it would then be offered an address from the 192.168.0.x scope
instead, if it's currently offering those to the wireless connections.