DHCP mix fixed addresses with dynamic addresses

> Hi,
>
> We’re using foreman in our environment, but sometimes we experience
> IP conflicts which are caused by the DHCP server (Internet Systems
> Consortium DHCP Server 4.1.1-P1). The problem:
>
> Host is provisioned by foreman and via foreman-proxy the host is
> also provisioned within DHCP, In dhcp.leases file I see:
>
> host blabla.netops {
> dynamic;
> hardware ethernet 00:50:56:a2:01:05;
> fixed-address 172.20.0.37;
> supersede server.filename = "pxelinux.0";
> supersede server.next-server = ac:14:00:01;
> supersede host-name = "blabla.netops";
> }
>
> So far so good, but when another host in the network requests an IP
> address the DHCP server offers the same IP address to another host:
>
> lease 172.20.0.37 {
> starts 3 2012/12/05 07:01:37;
> ends 3 2012/12/05 19:01:37;
> tstp 3 2012/12/05 19:01:37;
> cltt 3 2012/12/05 07:01:37;
> binding state active;
> next binding state free;
> hardware ethernet 00:50:56:a2:51:6d;
> }
>
> My dhcpd.conf is very basic:
>
> # cat /etc/dhcp/dhcpd.conf
> authoritative;
> omapi-port 7911;
> allow booting;
> allow bootp;
>
> subnet 172.20.0.0 netmask 255.255.240.0 {
> range 172.20.0.2 172.20.15.200;
> option domain-name-servers 172.20.0.1;
> option domain-name "netops";
> #option routers 172.20.0.1;
> filename "/pxelinux.0";
> next-server 172.20.0.1;
> }
>
> Some googling learned me that it's a bad idea to mix fixed addresses
> with dynamic addresses in the same range. For example see this post:
>
> http://www.mentby.com/Group/dhcp-users/mixing-fixed-address-host-declations-in-dhcpdconf-with-dynamic-entries-created-via-omapi.html
>
>
> Probably it's an idea to set a 'reserved flag' at a lease instead of
> a host-declaration?
>
> I never saw this issue, and never saw my dhcp server offering the same ip
twice, looking at the logs I could not find any thing related to this
problem.

saying that, if there is a better flag to reserve the ip on the dhcp side,
+1 from me - do you happen to know the variable name?

Ohad

··· On Wed, Dec 5, 2012 at 2:08 PM, Deuntje wrote:

I know that this is not directly a foreman-issue, but I think that
more foreman users may encounter this problem and hopefully somebody has
a solution or workaround for this issue.

Kind regards,
Dennis


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is this a multi dhcp server setup?

··· On Wed, Dec 5, 2012 at 2:23 PM, Ohad Levy wrote:

On Wed, Dec 5, 2012 at 2:08 PM, Deuntje google@dennisvandenbos.nl wrote:

Hi,

We’re using foreman in our environment, but sometimes we experience
IP conflicts which are caused by the DHCP server (Internet Systems
Consortium DHCP Server 4.1.1-P1). The problem:

Host is provisioned by foreman and via foreman-proxy the host is
also provisioned within DHCP, In dhcp.leases file I see:

host blabla.netops {
dynamic;
hardware ethernet 00:50:56:a2:01:05;
fixed-address 172.20.0.37;
supersede server.filename = “pxelinux.0”;
supersede server.next-server = ac:14:00:01;
supersede host-name = “blabla.netops”;
}

So far so good, but when another host in the network requests an IP
address the DHCP server offers the same IP address to another host:

lease 172.20.0.37 {
starts 3 2012/12/05 07:01:37;
ends 3 2012/12/05 19:01:37;
tstp 3 2012/12/05 19:01:37;
cltt 3 2012/12/05 07:01:37;
binding state active;
next binding state free;
hardware ethernet 00:50:56:a2:51:6d;
}

My dhcpd.conf is very basic:

cat /etc/dhcp/dhcpd.conf

authoritative;
omapi-port 7911;
allow booting;
allow bootp;

subnet 172.20.0.0 netmask 255.255.240.0 {
range 172.20.0.2 172.20.15.200;
option domain-name-servers 172.20.0.1;
option domain-name “netops”;
#option routers 172.20.0.1;
filename “/pxelinux.0”;
next-server 172.20.0.1;
}

Some googling learned me that it’s a bad idea to mix fixed addresses
with dynamic addresses in the same range. For example see this post:

http://www.mentby.com/Group/dhcp-users/mixing-fixed-address-host-declations-in-dhcpdconf-with-dynamic-entries-created-via-omapi.html

Probably it’s an idea to set a ‘reserved flag’ at a lease instead of
a host-declaration?

I never saw this issue, and never saw my dhcp server offering the same ip
twice, looking at the logs I could not find any thing related to this
problem.

saying that, if there is a better flag to reserve the ip on the dhcp side,
+1 from me - do you happen to know the variable name?

Ohad

I know that this is not directly a foreman-issue, but I think that
more foreman users may encounter this problem and hopefully somebody has
a solution or workaround for this issue.

Kind regards,
Dennis


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No, this DHCP server is a standalone.
In this post is described how a lease can be set to reserved:
https://lists.isc.org/pipermail/dhcp-users/2008-June/006535.html

Dennis.

··· Op woensdag 5 december 2012 13:45:01 UTC+1 schreef ohad het volgende: > > is this a multi dhcp server setup? > > > On Wed, Dec 5, 2012 at 2:23 PM, Ohad Levy <ohad...@gmail.com > > wrote: > >> >> >> >> On Wed, Dec 5, 2012 at 2:08 PM, Deuntje <goo...@dennisvandenbos.nl >> > wrote: >> >>> Hi, >>> >>> We’re using foreman in our environment, but sometimes we experience >>> IP conflicts which are caused by the DHCP server (Internet Systems >>> Consortium DHCP Server 4.1.1-P1). The problem: >>> >>> Host is provisioned by foreman and via foreman-proxy the host is >>> also provisioned within DHCP, In dhcp.leases file I see: >>> >>> host blabla.netops { >>> dynamic; >>> hardware ethernet 00:50:56:a2:01:05; >>> fixed-address 172.20.0.37; >>> supersede server.filename = "pxelinux.0"; >>> supersede server.next-server = ac:14:00:01; >>> supersede host-name = "blabla.netops"; >>> } >>> >>> So far so good, but when another host in the network requests an IP >>> address the DHCP server offers the same IP address to another host: >>> >>> lease 172.20.0.37 { >>> starts 3 2012/12/05 07:01:37; >>> ends 3 2012/12/05 19:01:37; >>> tstp 3 2012/12/05 19:01:37; >>> cltt 3 2012/12/05 07:01:37; >>> binding state active; >>> next binding state free; >>> hardware ethernet 00:50:56:a2:51:6d; >>> } >>> >>> My dhcpd.conf is very basic: >>> >>> # cat /etc/dhcp/dhcpd.conf >>> authoritative; >>> omapi-port 7911; >>> allow booting; >>> allow bootp; >>> >>> subnet 172.20.0.0 netmask 255.255.240.0 { >>> range 172.20.0.2 172.20.15.200; >>> option domain-name-servers 172.20.0.1; >>> option domain-name "netops"; >>> #option routers 172.20.0.1; >>> filename "/pxelinux.0"; >>> next-server 172.20.0.1; >>> } >>> >>> Some googling learned me that it's a bad idea to mix fixed addresses >>> with dynamic addresses in the same range. For example see this post: >>> >>> http://www.mentby.com/Group/dhcp-users/mixing-fixed-address-host-declations-in-dhcpdconf-with-dynamic-entries-created-via-omapi.html >>> >>> >>> Probably it's an idea to set a 'reserved flag' at a lease instead of >>> a host-declaration? >>> >>> I never saw this issue, and never saw my dhcp server offering the same >> ip twice, looking at the logs I could not find any thing related to this >> problem. >> >> saying that, if there is a better flag to reserve the ip on the dhcp >> side, +1 from me - do you happen to know the variable name? >> >> Ohad >> >>> I know that this is not directly a foreman-issue, but I think that >>> more foreman users may encounter this problem and hopefully somebody has >>> a solution or workaround for this issue. >>> >>> Kind regards, >>> Dennis >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Foreman users" group. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msg/foreman-users/-/crIRBi8YJpIJ. >>> To post to this group, send email to forema...@googlegroups.com >>> . >>> To unsubscribe from this group, send email to >>> foreman-user...@googlegroups.com . >>> For more options, visit this group at >>> http://groups.google.com/group/foreman-users?hl=en. >>> >> >> >

I was reading this thread
https://lists.isc.org/pipermail/dhcp-users/2007-August/004396.html
and it seems like this is:

  1. only used for multi server configuration?
  2. only relevant for leases (we are after all creating host reservations
    not leases).

Saying that, ISC dhcp documentation was always an interesting challenge to
me.

Ohad

··· On Wed, Dec 5, 2012 at 2:50 PM, Deuntje wrote:

https://lists.isc.org/pipermail/dhcp-users/2008-June/006535.html