Fedora Linux Support Community & Resources Center

Go Back   FedoraForum.org > Fedora 25/26 > Servers & Networking
FedoraForum Search

Forgot Password? Join Us!

Servers & Networking Discuss any Fedora server problems and Networking issues such as dhcp, IP numbers, wlan, modems, etc.

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 23rd July 2015, 01:18 PM
edfromhadria Offline
Registered User
 
Join Date: Jul 2012
Location: Hungary
Posts: 17
linuxfedorafirefox
Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Server?

Hello!

At our workplace we have a Windows DHCP server dolling out IPs. On the Windows server our admin can see 36 character MAC address from my laptop (Fedora 22 Gnome, ThinkPad T540p), with the last 12 being the actual MAC address. The other client sends their MAC address right except my machine.

I have no any idea why?

I've disabled ipv6 like this:

..]# echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
..]# sysctl -p

but it's still the same address is sent to the Windows Server.

Does someone have any idea what can i do to send right MAC address? Thank you in advance for any help you can provide.
Reply With Quote
  #2  
Old 23rd July 2015, 07:14 PM
flyingdutchman Offline
Registered User
 
Join Date: Jan 2015
Location: Al Ain, UAE
Posts: 674
macosfirefox
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

DHCP is handled by a program called dhclient. Read the dhclient and tcpdump man pages to figure out what is wrong.
__________________
--
Have fun!
http://www.aeronetworks.ca
Reply With Quote
  #3  
Old 27th July 2015, 11:02 AM
edfromhadria Offline
Registered User
 
Join Date: Jul 2012
Location: Hungary
Posts: 17
linuxfedorafirefox
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

Dear flyingdutchman!

What should i looking for about dhclient or tcpdump? I am not a linux expert.
Could you help me what should i try?

Our admin see looks like this:


After the 753bb...4cce begins my real MAC address with 5... What is those numbers before of my MAC address and how can i send only my Mac Address to the DHCP server?
Reply With Quote
  #4  
Old 27th July 2015, 02:35 PM
flyingfsck Offline
Registered User
 
Join Date: Aug 2010
Location: Al Ain, UAE
Posts: 1,999
macoschrome
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

Well, this is not a Linux problem per se. It is a DHCP and DNS networking problem. If you can debug and fix it on Linux, then you can fix it only any type of machine.

Do you have an IP address?
# ifconfig

Do you have a default route?
# route

Check whether the DNS works with ping or nslookup:
# nslookup www.yahoo.com

Do you get an address or a bunch of error messages?

See what is going on with tcpdump:
# tcpdump -nlX -i em0

Do you have a DNS server configured?
# cat /etc/resolve.conf

and so on.

Read the man pages for details.
Reply With Quote
  #5  
Old 18th August 2015, 06:51 PM
sheridan Offline
Registered User
 
Join Date: Jan 2008
Posts: 2
linuxchrome
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

edfromhadria,

As often happens in the Linux world, dhclient evolved to become more RFC compliant which can break software which is decidedly less so, e.g., your Microsoft DHCP service. You have two options:

1) Modify your Windows DHCP server and set aside a DHCP reservation according to the overblown MAC size address that appears in the lease entry. The downside to this approach is that it requires you to have change access to this server and the fix is a bit of a kludgey workaround as the overblown address may change as it is a superset of the actual 6 octet hardware address of your host.

2) The better option is to create (as root) an /etc/dhcp/dhclient.conf file (it probably won't exist in F21/22) on your Linux client with the following line:

Code:
send dhcp-client-identifier = hardware;
This line was present in Fedora versions prior to F21 but was removed when dhclient became RFC 4361-compliant. To make it work with older DHCP servers, this explicit line will cause the exact MAC address to be issued to the DHCP server rather than the server extracting it from the chaddr field of the DHCP packet.

Hope this works for you...and I hope you continue to stick with Fedora as it is a great operating system. If you are curious about this issue, you can find more info here.

--Wayne
Reply With Quote
  #6  
Old 16th September 2015, 10:59 PM
edfromhadria Offline
Registered User
 
Join Date: Jul 2012
Location: Hungary
Posts: 17
macossafari
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

Dear sheridan!

I've just come to write that i find (here: https://bugzilla.redhat.com/show_bug.cgi?id=560361 ) the solution of this problem but I see you wrote the right answer too!

Thank you so much, and my apologize for my late reaction.

ed
Reply With Quote
  #7  
Old 25th July 2017, 09:06 PM
marzo Offline
Registered User
 
Join Date: Nov 2007
Posts: 19
linuxfedorachrome
Re: Why sents 36 character MAC address from my laptop (Fedora22) to Windows DHCP Serv

Dear sheridan!

I have Fedora 26 with the same problem. I followed you answer and that solutioned the problem.

Thank you !
Reply With Quote
Reply

Tags
address, character, dhcp, fedora22, laptop, mac, sents, server, windows

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How do I find my DHCP server's address ToddAndMargo Using Fedora 12 22nd June 2015 05:10 AM
dnsmasq: failed to bind DHCP server socket: Address already in use taske Servers & Networking 3 9th November 2009 12:39 AM
No IP Address from DHCP Server on Wireless Network naimesh.thakkar Servers & Networking 15 27th May 2009 10:30 AM
Dhcp Server cannot assign static IP Address??? darkdragon Servers & Networking 10 10th February 2007 10:01 PM
Doing DHCP Kickstart with Windows DHCP Server wdtj Installation, Upgrades and Live Media 3 8th October 2004 02:24 AM


Current GMT-time: 10:27 (Monday, 21-08-2017)

TopSubscribe to XML RSS for all Threads in all ForumsFedoraForumDotOrg Archive
logo

All trademarks, and forum posts in this site are property of their respective owner(s).
FedoraForum.org is privately owned and is not directly sponsored by the Fedora Project or Red Hat, Inc.

Privacy Policy | Term of Use | Posting Guidelines | Archive | Contact Us | Founding Members

Powered by vBulletin® Copyright ©2000 - 2012, vBulletin Solutions, Inc.

FedoraForum is Powered by RedHat