RE: DHCP Manual Bindings

Marko,

If someone had to map a few very old and unique phones to different call
agents, while these phones were on the same VLAN and subnet (remote phones
over easyvpn scenario with local DHCP pool). The config is not intuitive, as
there is a relationship between parent and child pools and the way they are
structured. The main pool for the whole subnet has default router
configuration and host pools per device have hardware address and option 150
for each device.

I also have noticed that if client id is present some DHCP servers ignore
hardware address and will not match on it. I am not entirely sure about IOS
in this case.

Adel Abouchaev, CCIE# 12037, CISSP, MCSE

Technical Support Engineer

Netmasterclass LLC, Cisco Learning Partner

RFC821: adel_at_netmasterclass.net

E.164: +18886772669

HTTP: www.netmasterclass.net

From: petrsoft_at_gmail.com [mailto:petrsoft_at_gmail.com] On Behalf Of Petr
Lapukhov
Sent: Wednesday, November 17, 2010 11:28 AM
To: Marko Milivojevic
Cc: Adel Abouchaev; Cisco certification
Subject: Re: DHCP Manual Bindings

Yes, for those DHCP clients that do not include the "client-identifier"
option in DHCP messages. In such case, the DCHP server has to rely on
"chaddr" field in the packets, which (normally) equals the client's MAC
address (could be spoofed though :). One example of such behavior was the
default Linux DHCP client that did not supply the above-mentioned option.
This made configuring the DHCP server static bindings confusing at times
when you had a mix of Linux/Windows boxes on the segment.

Regards,

-- 
Petr Lapukhov, petr_at_INE.com
CCIE #16379 (R&S/Security/SP/Voice)
CCDE #20100007
Internetwork Expert, Inc.
http://www.INE.com <http://www.ine.com/> 
Toll Free: 877-224-8987
Outside US: 775-826-4344
2010/11/17 Marko Milivojevic <markom_at_ipexpert.com>
That said... I have one DHCP question. Does anyone know a
scenario/situation when using "hardware-address" inside host pool
actually does anything?
--
Marko Milivojevic - CCIE #18427
Senior Technical Instructor - IPexpert
FREE CCIE training: http://bit.ly/vLecture
Mailto: markom_at_ipexpert.com
Telephone: +1.810.326.1444
Web: http://www.ipexpert.com/
On Wed, Nov 17, 2010 at 17:29, Adel Abouchaev <adel_at_netmasterclass.net>
wrote:
> B  B  B  B Marko and Tyson are absolutely correct here.
>
> B  B  B  B To add a bit to the message on how to approach this situation
if you aren't sure why client ID or any other parameters aren't leading to a
correct DHCP assignment, the debug for DHCP is quite talkative and usually
answers any question within a minute. I have found it very useful during
troubleshooting DHCP issues for many occasions.
>
> Cheers,
>
> Adel Abouchaev, CCIE# 12037, CISSP, MCSE
>
> Technical Support Engineer
> Netmasterclass LLC, Cisco Learning Partner
> RFC821: adel_at_netmasterclass.net
> E.164: +18886772669
> HTTP: www.netmasterclass.net
>
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Marko Milivojevic
> Sent: Wednesday, November 17, 2010 8:10 AM
> To: Tyson Scott
> Cc: Steven Blasiol; Cisco certification
> Subject: Re: DHCP Manual Bindings
>
> Just to follow-up on Tyson's reply. This will probably work if you set
> "ip address dhcl client-identifier Fa0/0" on R1. If not, after certain
> IOS release (12.4somethingortheother) client identifier option is set
> to something else (see previous discussion on OSL for details).
>
> When you set the client-identifier option to be derived from the
> interface MAC address, it will still not be the MAC address alone. The
> MAC address will be prefixed by media type, which for Ethernet is "01.
> Therefore, your client-id becomes 01<MAC_ADDRESS>". You need to move
> the dot around a bit.
>
> For MAC address c002.0594.0000, client identifier becomes
> 01c0.0205.9400.00 -> just as Tyson wrote below.
>
> --
> Marko Milivojevic - CCIE #18427
> Senior Technical Instructor - IPexpert
>
> FREE CCIE training: http://bit.ly/vLecture
>
> Mailto: markom_at_ipexpert.com
> Telephone: +1.810.326.1444
> Web: http://www.ipexpert.com/
>
> On Wed, Nov 17, 2010 at 00:22, Tyson Scott <tscott_at_ipexpert.com> wrote:
>> That is because that will never be your client-identifier.
>>
>> ip dhcp pool LABMANUAL
>> B B host 10.0.12.77 255.255.255.0
>> B B client-identifier 01c0.0205.9400.00
>>
>> When you get the IP address you should be able to notice in the output of
>> "show ip dhcp bind" what the client identifier is showing up for when it
>> isn't working for you.
>>
>> Please let me know if this doesn't work for you. B If it doesn't work
please
>> provide the output of "show ip dhcp bind"
>>
>> Regards,
>>
>> Tyson Scott - CCIE #13513 R&S, Security, and SP
>> Managing Partner / Sr. Instructor - IPexpert, Inc.
>> Mailto: tscott_at_ipexpert.com
>>
>>
>> -----Original Message-----
>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>> Steven Blasiol
>> Sent: Tuesday, November 16, 2010 7:10 PM
>> To: Cisco certification
>> Subject: DHCP Manual Bindings
>>
>> I am having some problems in GNS3 setting manual ip address bindings. B
Here
>> are the relevant configs:
>>
>> (DHCP Client)R1 Fa0/0-------------------Fa0/0R2 (DHCP Server)
>>
>> Router1
>>
>> interface FastEthernet0/0
>> ip address dhcp client-id FastEthernet0/0 hostname CCIELAB
>> duplex auto
>> speed auto
>>
>>
>> Router2
>>
>> no ip dhcp conflict logging
>> !
>> ip dhcp excluded-address 10.0.12.1 10.0.12.50
>> !
>> ip dhcp pool LABMANUAL
>> B B host 10.0.12.77 255.255.255.0
>> B B client-identifier c002.0594.0000 (MAC of R1 Fa0/0)
>> B B client-name CCIELAB
>> !
>> ip dhcp pool LABDYNAMIC
>> B B network 10.0.12.0 255.255.255.0
>> B B domain-name ccie.com
>> B B default-router 10.0.12.1
>>
>>
>> When I have it configured like this I keep getting an address from the
>> LABDYNAMIC pool. B I thought maybe you could have two pools so I removed
the
>> DYNAMIC pool and I just don't get an address.
>>
>> i am obviously missing something and the documentation i have found so
far
>> is not really helpful.
>>
>> Thanks in advance.
>> --
>> Steven M. Blasiol
>>
>>
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