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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