Red Hat Bugzilla – Bug 203401
Hostname gets lost when using DHCP
Last modified: 2014-03-16 23:01:36 EDT
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Description of problem:
My small home network is served by an AVM FRITZ!Box  which provides internet access and manages local network configuration per DHCP.
Unfortunately the hostnames of my computers are always set to "noname" when using Fedora. When running Windows XP or MacOSX the name ist set right.
I could narrow down the problem to dhclient not sending dhcp-client-identifier after sending the hostname which the FRITZ!Box seems to want and Windows XP and MacOSX seem to send in form the MAC address of the network device.
I don't know who to blame. But the solution is fairly simple. I will attach a patch for /etc/sysconfig/network-scripts/ifup-eth. It just adds two lines which should be pretty harmless.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Set hostname in /etc/sysconfig/networking/devices/ifcfg-eth0 (DHCP_HOSTNAME). This can be done with system-config-network.
2. Connect your Fedora box to FRITZ!Box.
The hostname is set to "noname".
The hostname should be the one set for DHCP_HOSTNAME in /etc/sysconfig/networking/devices/ifcfg-eth0.
Created attachment 134583 [details]
Simple patch for /etc/sysconfig/network-scripts/ifup-eth
The patch assumes HWADDR is set; it will probably do something odd if it's not.
That's easy enough to pull in at that point, though.
Hm, in testing here, MacOSX does not appear to send a client identifier - how is
it working in that case for you?
Never mind, found it.
How do you have your box configured - static IPs via DHCP or dynamic? Is the
Fritz box doing mac address -> static address mapping?
Dynamic. But the FRITZ!Box seems to save the MAC address when it sees it the
first time, chooses an IP address and then gives the client the same IP address
every time. Actually you can only set a range which the box will use to choose
an IP address.
So, it's not the 'hostname' that gets lost, but it gets a different IP without
the identifier (so the hostname isn't valid)?
Created attachment 134595 [details]
Patch v2 - now with checks for HWADDR
No, the IP is the same every time. But if the client identifier is not sent the
FRITZ!Box seems to reset the hostname to "noname".
Hm, so this is the hostname in the router boxes' own DNS, yes?
I suspect this is something better changed after FC6 is out, to get more testing.
Yes, looks like "noname" is the default name the box gives to clients which do not send client identifiers. It
also replies this name to DNS queries.
Windows and MacOSX send 6 bytes, which represent the MAC address, as client
identifier, not a string of ASCII chars as I assumed. I think we can not imitate
this with 2 lines of script code.
But FRITZ!Box is satisfied with anything we send as client identifier. Therefore
we can also send DHCP_HOSTNAME and do not need further checks.
Created attachment 138505 [details]
Patch v3 - send DHCP_HOSTNAME as client id
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