IP allocation conflict resolution Introduction Normally in a DNS, only a single name is associated to a given IP. Further, the reverse search is possible allowing one to find the name from the IP. It is sometime convenient (or even necessary) to have more than one name sharing a given IP number. The common case is the default IP associated with a domain. This default IP is generally the IP number of the web server, making it convenient for web users. _L_i_n_- _u_x_c_o_n_f is trying to flag duplicate usage and help you manage properly your DNS. 11.. NNoorrmmaall ooppeerraattiioonn When updating a definition for a host name in a domain, Linuxconf checks if the IPs allocated are not already in use by another host in any of the domain managed by this DNS. If there is no other host using that (those) IP, linuxconf will updates the various records, including the reverse mappings (PTR records). If there is a conflict, a dialog is presented allowing full control on Linuxconf's behavior. 22.. SSoo tthheerree iiss aa ccoonnfflliicctt What are your options when there are such a conflict ? When more than one host are sharing one IP number, one is known as the official host and the reverse mapping points to it. So mostly you have this DNS relation. host.domain -> IP number IP number -> host.domain All other host names sharing the IP will only have the first line of this relation. Linuxconf enforces this. So when there is a conflict your options are: +o Cancel the dialog and pick another IP number +o Tell linuxconf that this host is the "main" one so linuxconf will use this host name to do the reverse mapping (and will delete any previous reverse mapping on this IP number). +o Tell linuxconf that this host is not the "main" one. Linuxconf won't update the reverse mapping. 33.. TThhee IIPP aallllooccaattiioonn ccoonnfflliicctt rreessoolluuttiioonn ddiiaalloogg You are allowed to enter up to 4 IP numbers per host name. If there is a conflict on at least one IP number, linuxconf will present you a dialog showing you each IP number and the suggested update mode. Mostly, linuxconf may or may not update the reverse mapping associated with each IP number. The dialog appears with a check box for each IP number. Those with a conflict have the check box in the "unchecked" state. This mean that if you simply "accept" the dialog as is, linuxconf won't update the reverse mapping of the IP numbers where there is a conflict. By switching the state of the check box, you effectivly tell linuxconf to update or leave unchanged the reverse lookup for the given IP. 44.. EEnntteerriinngg aann IIPP nnuummbbeerr ffoorr aa ddoommaaiinn Since this is common practice and a reverse mapping pointing to a domain is a bad practice (It must point to a host of the domain), linuxconf does not signal any conflict when entering IP numbers for a domain. (There should be a conflict indeed)