Wrong address assigned --- bottom bits of MAC address ignored ?
gary mazzaferro
garym at oedata.com
Thu Feb 28 21:48:19 UTC 2013
Thanks so much... I was just looking at books... I'll order that today. :)
cheers,
gary
On Thu, Feb 28, 2013 at 11:23 AM, Jim Glassford <jmglass at iup.edu> wrote:
> Hi Gary,
>
> I found helpful, "The DHCP Handbook" ISBN 1-57870-137-6, and looks like I
> need to get a newer addition. :-)
>
> <http://search.barnesandnoble.com/DHCP-Handbook/Ralph-E-Droms/e/9780672323270>
>
> jim
>
>
>
> On 2/28/2013 12:53 PM, gary mazzaferro wrote:
>>
>> Hi Glen,
>>
>> Thanks... This was the explanation I was looking for.. again thank you
>>
>> This should be in a practices guide, your description well written and
>> easily understood.
>>
>> Both you and Sten were correct, hosts must not be placed in the subnet
>> declaration. The server does act weird, it won't serve fixed addresses
>> unless they are in the range. But, then its a first come basis for
>> assignment.
>>
>> Now I have to figure out why the server is not seeing dhcp requests on
>> eth2.
>>
>> again thank you...
>>
>> cheers,
>> gary
>>
>>
>> On Thu, Feb 28, 2013 at 6:56 AM, Glenn Satchell
>> <glenn.satchell at uniq.com.au> wrote:
>>>
>>> Hi Gary
>>>
>>> Just to clarify a few things.
>>>
>>> You have two ethernet interfaces and two subnets. Are these physically
>>> separate subnets, ie using different switches, or different vlans on one
>>> switch?
>>>
>>> Or are they sharing the same broadcast domain, with both subnets going
>>> over the same wire and traffic visible on both ports? In dhcpd this is
>>> termed a shared-network.
>>>
>>> This is important, because if it's a shared network the client may be
>>> sending all requests out eth0. This is the mac the server sees and it
>>> responds as you have seen.
>>>
>>> Is the second ethernet port being assigned any IP address?
>>>
>>> For a host statement with fixed-address the dhcp server takes some short
>>> cuts. One of these side effects is that it does not record an entry in
>>> the
>>> leases file. So the dhcpd.leases entry you see is for allocation from the
>>> dynamic range. Once the dhcp server has allocated an address to a client
>>> it will continue to offer the same address each time that client asks for
>>> it unless a different client is already using it.
>>>
>>> The dhcp server will not allocate a fixed-address if it puts the client
>>> in
>>> the wrong subnet. ie if the request came in via a relay or direct
>>> connection that indicated it was in a different subnet it would allocate
>>> one from the dynamic range of the appropriate subnet.
>>>
>>> Fourthly, if you put an address in the "range" then the server is able to
>>> allocate that address even if there is a host entry with fixed-address
>>> also using that same address. It is a race to see who gets it first. Even
>>> though the dhcp server will ping the address before offering it, if a
>>> firewall on the client (common on windows since XP) blocks icmp then it
>>> will not receive a response. So fixed-addresses should not be included in
>>> range statements.
>>>
>>> In this case you want
>>>
>>> range 172.31.1.17 172.31.1.30;
>>> and
>>> range 10.96.165.17 10.96.165.44;
>>>
>>> The dhcp server thinks 90:e2:ba:0c:0d:50 is connected to the 172.31.1.0
>>> subnet and offers a dynamic IP from the range in that subnet. It's just a
>>> coincidence that it chose 172.31.1.16, perhaps that was the first free
>>> address. Now that it is in the dhcpd.leases file it will keep offering
>>> that address. To clear that lease entry, stop the dhcp server process,
>>> edit the dhcpd.leases file and remove all leases for that ip address
>>> (there may be several entries in the file) and then start the dhcpd
>>> process.
>>>
>>> As others have said putting host statements in the subnet definition
>>> almost never does what you want, and causes confusion when clients
>>> receive
>>> odd responses. You are very strongly encouraged to move them out of the
>>> subnet definition. A simple comment will serve much better at documenting
>>> the desired information.
>>>
>>> Please keep posting responses and more questions. The dhcp server is a
>>> very flexible piece of software, so sometimes it takes a bit of tweaking
>>> to do what you want. The important part you need to do is describe your
>>> network topology to us - then we can help with how the config should go.
>>>
>>> regards,
>>> -glenn
>>>
>>>
>>> On Thu, February 28, 2013 11:15 pm, Sten Carlsen wrote:
>>>>
>>>> On 28/02/13 13:00, gary mazzaferro wrote:
>>>>>
>>>>> Hi Sten,
>>>>>
>>>>> Thank you for the reply and the explanation...
>>>>>
>>>>> I do understand host statements are global. Placing them under the
>>>>> subnets was for documentation than anything else.
>>>>>
>>>>> The explanation doesn't address the issue I'm experiencing, IP address
>>>>> for 172.31.1.16 is already provisioned for mac address
>>>>> 90:e2:ba:0c:0d:51 and in my reading of the documentation, the server
>>>>> should not be offering to the incoming request using mac address
>>>>> 90:e2:ba:0c:0d:50.
>>>>
>>>> Well, this is probably another misunderstanding, if I understand you
>>>> correctly. Putting a fixed address into a host statement does NOT
>>>> reserve it for any purpose. The server will happily hand it out to any
>>>> who may ask IF it is in the pool/range of the subnet the discover
>>>> arrives at.
>>>> My guess is that your eth1 has an address in the 172.31.1.x range - this
>>>> would mean that it will get an address in that range (or no addresss at
>>>> all) whatever you put in the host statement.
>>>>
>>>> Again I will warn against putting host statements in the subnets, in
>>>> this case it will mean that the following options will be given even
>>>> when the address is:
>>>>
>>>> Feb 27 18:07:54 DCAPXEserver dhcpd: DHCPACK on 172.31.1.16 to
>>>> 90:e2:ba:0c:0d:50 (hd-node4) via eth1
>>>>
>>>> option domain-name "wbu.mydomain.com";
>>>> option domain-name-servers 10.96.191.251,10.119.248.254;
>>>> option routers 10.96.164.1;
>>>> default-lease-time 3456000;
>>>> max-lease-time 34560000;
>>>>
>>>> Basic point is DON'T put fixed address statements in the range you give
>>>> the server to hand out, there will not be any reservations made. Sorry I
>>>> missed this at first reading.
>>>>>
>>>>> cheers,
>>>>> gary
>>>>>
>>>>> On Wed, Feb 27, 2013 at 7:36 PM, Sten Carlsen <stenc at s-carlsen.dk>
>>>>> wrote:
>>>>>>
>>>>>> It seems that you think the host statement can have a limited scope,
>>>>>> limited
>>>>>> to a subnet. That is not correct, host statements are global wherever
>>>>>> they
>>>>>> are placed. The bad thing about putting them into subnets is that they
>>>>>> will
>>>>>> inherit options from the subnet even if they get addresses from
>>>>>> another
>>>>>> subnet.
>>>>>>
>>>>>> The server will hand out an address corresponding to the subnet it
>>>>>> sees
>>>>>> the
>>>>>> discover coming from, it will use the fixed address only if it matches
>>>>>> the
>>>>>> subnet the discover comes from, else it will use an address from the
>>>>>> subnet's pool.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 28/02/13 2:36, gary mazzaferro wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Maybe someone can help me..
>>>>>>
>>>>>> I have an intel card with 4 ports.. with incremental mac addresses.
>>>>>>
>>>>>> I'm trying to to use the dhcp server 4.2.3.P2 to assign two subnets
>>>>>> based on mac addresses, The server is assigning the first address it
>>>>>> finds close to the mac address. Not sure if my config file is bad..
>>>>>>
>>>>>> 90:e2:ba:0c:0d:50 should be 10.96.165.16
>>>>>> 90:e2:ba:0c:0d:51 should be 172.31.1.16
>>>>>>
>>>>>> 90:e2:ba:0c:0d:50 sees and offer of 172.31.1.16
>>>>>>
>>>>>> Feb 27 18:07:53 DCAPXEserver dhcpd: DHCPDISCOVER from
>>>>>> 90:e2:ba:0c:0d:50
>>>>>> via
>>>>>> eth1
>>>>>> Feb 27 18:07:54 DCAPXEserver dhcpd: DHCPOFFER on 172.31.1.16 to
>>>>>> 90:e2:ba:0c:0d:50 (hd-node4) via eth1
>>>>>> Feb 27 18:07:54 DCAPXEserver dhcpd: DHCPREQUEST for 172.31.1.16
>>>>>> (172.31.1.10) from 90:e2:ba:0c:0d:50 (hd-node4) via eth1
>>>>>> Feb 27 18:07:54 DCAPXEserver dhcpd: DHCPACK on 172.31.1.16 to
>>>>>> 90:e2:ba:0c:0d:50 (hd-node4) via eth1
>>>>>>
>>>>>> Can some one please help me ?
>>>>>>
>>>>>> lease file:
>>>>>> # The format of this file is documented in the dhcpd.leases(5) manual
>>>>>> page.
>>>>>> # This lease file was written by isc-dhcp-4.2.3-P2
>>>>>>
>>>>>> server-duid "\000\001\000\001\030\224\215R\000\014)\375\317\242";
>>>>>>
>>>>>> lease 172.31.1.16 {
>>>>>> starts 4 2013/02/28 01:07:54;
>>>>>> ends 2 2013/04/09 01:07:54;
>>>>>> cltt 4 2013/02/28 01:07:54;
>>>>>> binding state active;
>>>>>> next binding state free;
>>>>>> rewind binding state free;
>>>>>> hardware ethernet 90:e2:ba:0c:0d:50;
>>>>>> client-hostname "hd-node4";
>>>>>> }
>>>>>>
>>>>>> option domain-name-servers 172.31.1.10;
>>>>>> default-lease-time 3456000;
>>>>>> ddns-update-style none;
>>>>>> authoratative ;
>>>>>> subnet 172.31.1.0 netmask 255.255.255.0 {
>>>>>> option domain-name "dca.wbu.mydomain.com";
>>>>>> option domain-name-servers 172.31.1.10;
>>>>>> option routers 172.31.1.1;
>>>>>> default-lease-time 3456000;
>>>>>> max-lease-time 34560000;
>>>>>> range 172.31.1.11 172.31.1.30;
>>>>>> host hd-namenode-data1 {
>>>>>> option host-name "hd-namenode";
>>>>>> hardware ethernet 00:0c:29:c6:82:be;
>>>>>> filename "vmunix.hd-namenode";
>>>>>> fixed-address 172.31.1.11;
>>>>>> }
>>>>>> host pikespeak1 {
>>>>>> hardware ethernet 00:00:c0:5d:bd:95;
>>>>>> filename "vmunix.pikepeak";
>>>>>> server-name "pikespeak1";
>>>>>> }
>>>>>> host node1-data1 {
>>>>>> option host-name "hd-node1";
>>>>>> hardware ethernet 00:0c:29:c1:6e:35;
>>>>>> filename "vmunix.stargo";
>>>>>> fixed-address 172.31.1.13;
>>>>>> }
>>>>>> host node2-data1 {
>>>>>> option host-name "hd-node2";
>>>>>> hardware ethernet 00:0c:29:b8:af:f3;
>>>>>> filename "vmunix.stargo";
>>>>>> fixed-address 172.31.1.14;
>>>>>> }
>>>>>> host node3-data1 {
>>>>>> option host-name "hd-node3";
>>>>>> hardware ethernet 00:0c:29:04:65:ee;
>>>>>> filename "vmunix.stargo";
>>>>>> fixed-address 172.31.1.15;
>>>>>> }
>>>>>> host node4-data1-stargo {
>>>>>> option host-name "hd-node4";
>>>>>> hardware ethernet 90:e2:ba:0c:0d:51;
>>>>>> filename "vmunix.stargo";
>>>>>> fixed-address 172.31.1.16;
>>>>>> }
>>>>>> }
>>>>>> subnet 10.96.165.0 netmask 255.255.255.0 {
>>>>>> option domain-name "wbu.mydomain.com
>>>>>> ";
>>>>>> option domain-name-servers 10.96.191.251,10.119.248.254;
>>>>>> option routers 10.96.164.1;
>>>>>> default-lease-time 3456000;
>>>>>> max-lease-time 34560000;
>>>>>> range 10.96.165.11 10.96.165.44;
>>>>>> host hd-namenode-mgt {
>>>>>> option host-name "hd-namenode";
>>>>>> hardware ethernet 00:0c:29:c6:82:b4;
>>>>>> filename "vmunix.hd-namenode";
>>>>>> fixed-address 10.96.165.11;
>>>>>> }
>>>>>> host hd-node1-mgt {
>>>>>> option host-name "hd-node1";
>>>>>> hardware ethernet 00:0c:29:c1:6e:2b;
>>>>>> filename "vmunix.hd-node1";
>>>>>> fixed-address 10.96.165.13;
>>>>>> }
>>>>>> host hd-node2-mgt {
>>>>>> option host-name "hd-node2";
>>>>>> hardware ethernet 00:0c:29:b8:af:9e;
>>>>>> filename "vmunix.hd-node2";
>>>>>> fixed-address 10.96.165.14;
>>>>>> }
>>>>>> host hd-node3-mgt {
>>>>>> option host-name "hd-node3";
>>>>>> hardware ethernet 00:0c:29:04:65:e4;
>>>>>> filename "vmunix.hd-node3";
>>>>>> fixed-address 10.96.165.15;
>>>>>> }
>>>>>> host hd-node4-mgt-stargo {
>>>>>> option host-name "hd-node4";
>>>>>> hardware ethernet 90:e2:ba:0c:0d:50;
>>>>>> filename "vmunix.hd-node4";
>>>>>> fixed-address 10.96.165.16;
>>>>>> }
>>>>>> }
>>>>>> _______________________________________________
>>>>>> dhcp-users mailing list
>>>>>> dhcp-users at lists.isc.org
>>>>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Best regards
>>>>>>
>>>>>> Sten Carlsen
>>>>>>
>>>>>> No improvements come from shouting:
>>>>>> "MALE BOVINE MANURE!!!"
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> dhcp-users mailing list
>>>>>> dhcp-users at lists.isc.org
>>>>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>>>
>>>>> _______________________________________________
>>>>> dhcp-users mailing list
>>>>> dhcp-users at lists.isc.org
>>>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>>
>>>> --
>>>> Best regards
>>>>
>>>> Sten Carlsen
>>>>
>>>> No improvements come from shouting:
>>>> "MALE BOVINE MANURE!!!"
>>>>
>>>> _______________________________________________
>>>> dhcp-users mailing list
>>>> dhcp-users at lists.isc.org
>>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>>
>>>
>>> _______________________________________________
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>>> dhcp-users at lists.isc.org
>>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
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