Attachment 306357 Details for Bug 435599 – mmcallis reply to comment# 6

mmcallis reply to comment# 6

dhcpbugzillareply (text/plain), 4.14 KB, created by Murray McAllister on 2008-05-22 10:16:47 UTC

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Creator: Murray McAllister

Created: 2008-05-22 10:16:47 UTC

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>Hi,
>
>Please do not hesitate to let us know if anything in this section is incorrect, or if anything could be changed to make it clearer. Also, apologies if you know the following, I hope I don't sound like I'm talking down to you :(
>
>I tried to make the content and configuration examples generic, while answering your questions at the same time. I'll try to answer them here, and use the documentation as a reference:
>
>"- we were unable to configure DHCP server with the same workstation NAME in
>*different* subnets (DHCP service won't start afterwards);"
>
>Are you saying "NAME" is the output of the "hostname" command, eg, the name in "/etc/hosts", and the value of "HOSTNAME" in "/etc/sysconfig/network".
>
>I'm not sure what you mean here. Are you trying to use *DHCP to assign* 2 computers with the same hostname (eg, the output of the "hostname" command, or do you mean you have something such as the following, in "/etc/dhcpd.conf":
>
>host test1 {
>	  hardware ethernet xxxxxx;
>	  fixed-address xxxxxx;
>}
>
>host test1 {
>	hardware ethernet xxxxxx;
>	fixed-address yyyyyy;
>}
>
>This will fail; however, the next example is valid, because the "hardware ethernet" address is used to identify computers, not the name, which, in the previous case, would be "test1":
>
>host test0 {
>	  hardware ethernet xxxxxx;
>	  fixed-address xxxxxx;
>}
>
>host test1 {
>	hardware ethernet xxxxxx;
>	fixed-address yyyyyy;
>}
>
>I tried to cover this in "21.4.1. Host Configuration, Configuring a single system for multiple networks", noting that, that the example has different names for each "host" declaration, but each "host" declaration has the same MAC address, but a "fixed-address" in different subnets. When you move that system around, and it sends a DHCP request, first the "fixed-address" statements will be checked, until it finds one in the correct subnet, then, the "hardware ethernet" address will be used to identify the host (the DHCP server will get the MAC/hardware address from the client system when the client sends a DHCP request/broadcast).
>
>"host" declarations are global, so defining them in "subnet" declarations won't change the way addresses are assigned, or how systems are identified (this is what the "fixed-address" and "hardware ethernet" options are for).
>
>
>"- we just wanted to know how to *exclude* an interface from the list, if
>possible ("listen on all interfaces except this");"
>
>I tried to cover this in "21.4. Configuring a Multihomed DHCP Server":
>
>---
>
> If a system has three network interfaces cards -- eth0, eth1, and eth2 -- and it is only desired that the DHCP daemon listens on eth0, then only specify eth0 in /etc/sysconfig/dhcpd:
>
>DHCPDARGS="eth0";
>
>---
>
>If you have 3 network interfaces, the DHCP daemon will listen on all of them, unless you specify interfaces in "/etc/sysconfig/dhcpd". So, to *exclude* them, only *include* the interfaces you want in "/etc/sysconfig/dhcpd".
>
>"- we needed to know how to configure alternate hardware addresses (say a laptop
>that connects to the same network, in one situation by wire, in other by radio,
>and requests IP address from the same DHCP server)"
>
>This should all happen automatically, but I covered this in "21.4.1. Host Configuration, Configuring systems with multiple network interfaces". For a single system that has ethernet and wireless, each interface will have a different MAC address, so you need multiple host declarations, that both specify different "hardware ethernet" addresses:
>
>host ethernet {
>	hardware ethernet 00:1a:6b:6a:2e:0b;
>	fixed-address 10.0.0.18;
>}
>
>host wireless {
>	hardware ethernet 00:1A:6B:6A:27:3A;
>	fixed-address 10.0.0.18;
>}
>
>Note: you only need to do this if *you* want to give it a certain IP address.
>
>Or, are you talking about how to configure the interface, on the system, to actually use DHCP? This can be done using the /etc/sysconfig/network-scripts/ifcfg-[interface] scripts (use "BOOTPROTO=dhcp"). The latter should all be handled by NetworkManager...
>
>Keep replying if this does not make sense, or answer your questions ;)
>
>Also, I had SELinux denials, so you might want to keep an eye on this: https://bugzilla.redhat.com/show_bug.cgi?id=209043
>You might not have access...basically it is asking for more details DHCP/SELinux docs.
>

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