Re: hostnames and interfaces
My non-technical understanding: * A BSD system has a fully qualified domain name that is set and retrieved by the hostname(1) command. This is normally defined in /etc/rc.conf and considered the 'true name' of the system. If this name does not resolve to an IP address, many network services will complain (such as sendmail). If this IP address is not configured on an interface on the system, many things will get confused (such as routing). * You can also configure other interfaces, either on extra network cards or using the alias option of ifconfig(8). These interfaces should have different IP addresses, and names are optional (but convenient). * Any IP address can have extra names, either in /etc/hosts or on a nameserver. The 'canonical' name should probably come first. Your average BSD system will have 1 hostname that resolves to 1 address configured on its single network interface. The /etc/hosts file will map this address to the FQ hostname, and probably also to the short version for convenience. It will also have the name localhost, resolving to 127.0.0.1 and configured on lo0, again using /etc/hosts for resolution. Anything beyond that is up to you... - Original Message - From: paul van den bergen [EMAIL PROTECTED] Subject: hostnames and interfaces hey all, I first encountered networking in CISCO land... where IP addresses and host names seem to be associated... what is the freeBSD way? AFAICS, a machine has a defined name regardless of howmany interfaces it has. if one splits the world up into hosts (one interface) and routers (multiple interfaces) can one define multiple hostnames? to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? -- Dr Paul van den Bergen Centre for Advanced Internet Architectures caia.swin.edu.au [EMAIL PROTECTED] IM:bulwynkl2002 And some run up hill and down dale, knapping the chucky stones to pieces wi' hammers, like so many road makers run daft. They say it is to see how the world was made. Sir Walter Scott, St. Ronan's Well 1824 ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED] ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: hostnames and interfaces
On Fri, Nov 21, 2003 at 12:17:30PM +1100, paul van den bergen wrote: I first encountered networking in CISCO land... where IP addresses and host names seem to be associated... what is the freeBSD way? AFAICS, a machine has a defined name regardless of howmany interfaces it has. if one splits the world up into hosts (one interface) and routers (multiple interfaces) can one define multiple hostnames? to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? Good question. Yes, this can be a problem with a multi-homed host: not really in any functional sense, but for organizational purposes. Any machine will have a hostname -- that is the name which gets printed in shell prompts and that the system uses by default to identify itself for such services as SMTP servers, LDAP, NIS, HTTP etc. The hostname is set by (surprise, surprise) the hostname(1) command using the data from /etc/rc.conf. This is generally recorded in /etc/hostnames, possibly with the names of various other local machines around the place because that's the one lookup system that's always available even when the network isn't up. But /etc/hostnames doesn't have to be used at all: I generally prefer to have the DNS be *the* unique data source for this sort of thing, so my /etc/hostnames files are pretty skeletal. Relying on the DNS leads to the use of hierarchical domain names and yet another religious argument: if the FQDN is 'foo.example.com' do you set the hostname to just 'foo' or do you use the fully qualified domain name as the hostname? The problem with using just 'foo' is that there is no general mechanism for telling the system what the rest -- the 'network part' of the name -- should be.[1] As good sys-admins we should be allergic even to the possibility of things going horribly wrong, and using the FQDN as the hostname closes off several potential trouble spots. However using the hostname as the default for all of the various services is generally only a convention. Those services can usually be configured to use whatever names you may imagine: role based names (www.example.com) are fairly common -- which is useful if you need to swap out machines for maintenance as you can just switch the role-name to an alternative server fairly simply. This also allows you to run 'virtual' servers: multiple instances of the same service on one machine. Since these services are generally networked based, they have to have an IP number associated with them: most of the time a CNAME record in the DNS will do, but some things like SMTP MXes or HTTPS virtual hosts need real A records. Now, most of this discussion has implicitly assumed that we're using a machine with a single network interface and just one IP number. For a big server, that's probably not going to be the case -- there may well be several IP numbers configured on a single interface (have to do this for eg. hosting multiple HTTPS virtual hosts on one machine) or several network interfaces, either to provide redundancy against failure of network kit or to allow the machine to have direct connections to several physical networks. In this case, it's perfectly reasonable to have all of: * the machine hostname as an A record configured in the DNS to return a list of all of the interface IP numbers, and corresponding PTR records. * individual domain names as A records that resolve to each of the IP numbers on the interfaces, or to the principal address on each interface, or to per-network IP numbers, and corresponding PTR records: together with the above, this means that looking up the IP number can return several hostnames. * role based names that can include all combinations of all of the above, either as A+PTR combinations or as CNAMES. Having several host names resolving to the same IP number is not a problem. Of course, being good DNS admins we will set up PTR records to do the inverse lookups. Personally I feel that having PTR records that return several domain names is perfectly valid, but there's various old documentation that insists the sky will fall if you do things like that.[2] In summary the whole relationship between host and domain names and IP numbers is defined by whatever works for you... Cheers, Matthew [1] There was for a long time a confusion between the NIS domain name and DNS based names, especially on Solaris machines. However NIS and DNS are separate systems and don't have to use the same domain structure at all. Nowadays LDAP is taking over from NIS, and again this has it's own hierarchical structure although one increasingly popular layout is to mimic the DNS hierarchy. The default domain or search path in /etc/resolv.conf is sort of going in the right direction, but there's no rule that says
Re: hostnames and interfaces
On Thu, 20 Nov 2003 20:42:33 -0500 Marty Landman [EMAIL PROTECTED] granted us these pearls of wisdom: At 08:17 PM 11/20/2003, paul van den bergen wrote: to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? Hey, sounds like you understand things so well you see the void in the forest. As a newbie I'm still just trying to keep my head from twisting off at long enough intervals to define some of the questions. Like, given I have 5 boxes - 1 fbsd 4 windoz though maybe that proportion will change in a time :) - and each has their own ip adr and I have two apaches installed does that mean I can setup a max of 5 different domain level websites on my intranet? Or 10? Or infinite (well, this is reality I hope so...) The daemons are afoot, my ponderings do not affect them. Hi, Let me see if I can shed some light on this issue for you. To the best of my knowledge a FBSD system can have only one hostname however it can have as many aliases as you wish. The setup of aliases is acheived via DNS rather than assigning hostnames per interface. Where you have multiple machines you would assign multiple hostnames whether they be from different domains or not. $ host mail.meibin.net mail.meibin.net is a nickname for kyoto.meibin.net kyoto.meibin.net has address 220.111.132.28 per the above the actual host name for the system is kyoto, it's FQDN is kyoto.meibin.net and it has the alias of mail.meibin.net rather than the host name of mail.meibin.net . Apache and loads of other software support virtual hosting and defining a name in an apache configuration has little to do with the actual underlying system hostname. That being said virtual hosts don't work well if DNS was not set correctly for them. You can also configure your NIC to answer to multiple IP addresses and then configure your Apache to treat each as a virtual host with a separate hostname/URL. Yes, you have to have whoever is serving DNS for you (either yourself, your ISP or some DNS service) set up to translate IP - hostname and if it involves a new Domain name, you have to register it with the appropriate registering agency. Most of our sites use a separate IP for each virtual host for various reasons. But, you can also have multiple aliases per IP address as the poster indicates. jerry HTH LukeK ___ ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: hostnames and interfaces
At 10:35 AM 11/21/2003, Jerry McAllister wrote: You can also configure your NIC to answer to multiple IP addresses and then configure your Apache to treat each as a virtual host with a separate hostname/URL. Yes, you have to have whoever is serving DNS for you (either yourself, your ISP or some DNS service) set up to translate IP - hostname Jerry, thanks for trying but I don't know what this means (I've heard this remark so many times myself from others...). Yikes, I'm just a blathering idiot. :( Marty Landman Face 2 Interface Inc 845-679-9387 Sign On Required: Web membership software for your site Make a Website: http://face2interface.com/Home/Demo.shtml ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: hostnames and interfaces
At 10:35 AM 11/21/2003, Jerry McAllister wrote: You can also configure your NIC to answer to multiple IP addresses and then configure your Apache to treat each as a virtual host with a separate hostname/URL. Yes, you have to have whoever is serving DNS for you (either yourself, your ISP or some DNS service) set up to translate IP - hostname Jerry, thanks for trying but I don't know what this means (I've heard this remark so many times myself from others...). Yikes, I'm just a blathering idiot. :( Well, I am not the best one to explain in detail. For this specific item, your best bet might be to study the Apache documentation on doing virtual hosts and maybe do some searching on the net (Google, etc) on the subject. Generally, it seems like there are actuall several questions being asked in this series of posts and I am having trouble figuring out what the core issue is.Hostnames and IPs are used on the net to address machines. Some of these can be 'virtual' machines that are hosted by machines that are set up to respond to a lot of either/or hostnames and IPs. Each actual machine that lives on the net will have a specific hostname and IP address that is its own and all the others that it answers to are considered either virtual addresses or aliases.A DNS server sorts out the relationships and reports the matchings between IPs and hostnames. You can run your own DNS server, especially if you have a lot of machines and your own domain, or you can arrange with another entity, such as your ISP or another DNS service to do that for you. If you are not connected to the net, it doesn't matter what you call your machine or how many aliases you create or what IPs you use, though you might want to stick to the designated private IP ranges if you create your own intranet even if it is not connected to the internet. There is no limit other than practical ones that I know of to how many aliases/virtual hosts you create if you are running an intranet that is not connected to the internet. If you connect to the internet, the domain you are using must be registered with a registering service. The service you use depends on the top level element of the name (.com .net, .org, .edu, .cn, .fr, etc) Your ISP will normally be the best one to help you with that (except that some ISPs are decidedly unhelpful; then you have to go looking) A fully Qualified Host Name consists of two main parts. A machine name such as 'mypc' and a domain name such as concern.com. They are assembled in to a FQHN (Fully Qualified Host Name) - as mypc.concern.com in this example. During installation, when it asks for hostname, it wants a Fully Qualified Hostname if you are going to be connected to the internet. You might just as well fake one if you are not going to be on the internet just to be consistent, but you can put just a single string if you want. IP addresses must be in the form xxx.xxx.xxx.xxx unless you are playing with IPV6 and if you are, you should know all this already so stop reading. There is often much misspeak about these. The full qualified hostname is often called a domain name, for example when only the last part is really the domain name. Plus, the term hostname is used to refer to both/either the single machine part of the name such as 'mypc' above and the fully qualified hostname 'mypc.concern.com' as above. This leads to much confusion and I wish we had better names. But, that is the way it is. The domain name 'concern.com' must be registered with the service handling .com. Then whoever owns the 'concern.com' domain allows or directs hostnames to use it. If you registered the domain name, then you decide. When the 'concern.com' domain name is registered, you have to tell the service what DNS server will be providing DNS service for that domain. It may be you if you registered the domain name and have a DNS server or it might be some other system, such as one run by your ISP or another company that runs DNS servers for hire.Whenever you create a host that resides in the domain, such as 'mypc' in 'mypc.concern.com' an entry must be made in whatever DNS server that is handling the 'concern.com' domain. That is required before it will do correct translation. The physical machine that is mypc on the concern.com domain may answer to lots of host names and even lots of IPs. There are two parts to making this happen. The 'mypc' machine must be set up to respond to all those host names besides its own name. If it involves additional IP address (an alias) it is done in a rc.conf ifconfig alias statement (or we actually put those in a rc.conf.local file and add an include just to keep things a little more clean and clear), and/or in the software that is expected to respond to it, such as Apache. If it is only a different hostname, it can be done only by configuring the software that responds to it. For Apache, for example, you
Re: hostnames and interfaces
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On Nov 20, 2003, at 5:42 PM, Marty Landman wrote: At 08:17 PM 11/20/2003, paul van den bergen wrote: to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? Hey, sounds like you understand things so well you see the void in the forest. As a newbie I'm still just trying to keep my head from twisting off at long enough intervals to define some of the questions. Like, given I have 5 boxes - 1 fbsd 4 windoz though maybe that proportion will change in a time :) - and each has their own ip adr and I have two apaches installed does that mean I can setup a max of 5 different domain level websites on my intranet? Or 10? Or infinite (well, this is reality I hope so...) This is more of an Apache question than a FreeBSD question. Apache allows you to set up virtual hosts on a per-IP basis or with many hosts using a single IP address. So, you are only limited in hosts to the restrictions of your hardware and installation of Apache. Mike - -- Michael K. SmithNoaNet 206.219.7116 (work) 206.579.8360 (cell) [EMAIL PROTECTED]http://www.noanet.net -BEGIN PGP SIGNATURE- Version: PGP 8.0.3 iQA/AwUBP76RfZzgx7Y34AxGEQI2iwCfW4Q/llLkDvSyh2c/bx9Xv5ws52gAniD3 kTcpWMn3tNAkpDUpPPhIpx5L =RYFc -END PGP SIGNATURE- ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
hostnames and interfaces
hey all, I first encountered networking in CISCO land... where IP addresses and host names seem to be associated... what is the freeBSD way? AFAICS, a machine has a defined name regardless of howmany interfaces it has. if one splits the world up into hosts (one interface) and routers (multiple interfaces) can one define multiple hostnames? to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? -- Dr Paul van den Bergen Centre for Advanced Internet Architectures caia.swin.edu.au [EMAIL PROTECTED] IM:bulwynkl2002 And some run up hill and down dale, knapping the chucky stones to pieces wi' hammers, like so many road makers run daft. They say it is to see how the world was made. Sir Walter Scott, St. Ronan's Well 1824 ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: hostnames and interfaces
At 08:17 PM 11/20/2003, paul van den bergen wrote: to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? Hey, sounds like you understand things so well you see the void in the forest. As a newbie I'm still just trying to keep my head from twisting off at long enough intervals to define some of the questions. Like, given I have 5 boxes - 1 fbsd 4 windoz though maybe that proportion will change in a time :) - and each has their own ip adr and I have two apaches installed does that mean I can setup a max of 5 different domain level websites on my intranet? Or 10? Or infinite (well, this is reality I hope so...) The daemons are afoot, my ponderings do not affect them. Marty Landman Face 2 Interface Inc 845-679-9387 Sign On Required: Web membership software for your site Make a Website: http://face2interface.com/Home/Demo.shtml ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: hostnames and interfaces
On Thu, 20 Nov 2003 20:42:33 -0500 Marty Landman [EMAIL PROTECTED] granted us these pearls of wisdom: At 08:17 PM 11/20/2003, paul van den bergen wrote: to expand on this, there is a potential many to many relationship here between host names and IP addresses (strickly speaking that is what dns etc sees?) how dose BSD define this? how does one define this using BSD? Hey, sounds like you understand things so well you see the void in the forest. As a newbie I'm still just trying to keep my head from twisting off at long enough intervals to define some of the questions. Like, given I have 5 boxes - 1 fbsd 4 windoz though maybe that proportion will change in a time :) - and each has their own ip adr and I have two apaches installed does that mean I can setup a max of 5 different domain level websites on my intranet? Or 10? Or infinite (well, this is reality I hope so...) The daemons are afoot, my ponderings do not affect them. Hi, Let me see if I can shed some light on this issue for you. To the best of my knowledge a FBSD system can have only one hostname however it can have as many aliases as you wish. The setup of aliases is acheived via DNS rather than assigning hostnames per interface. Where you have multiple machines you would assign multiple hostnames whether they be from different domains or not. $ host mail.meibin.net mail.meibin.net is a nickname for kyoto.meibin.net kyoto.meibin.net has address 220.111.132.28 per the above the actual host name for the system is kyoto, it's FQDN is kyoto.meibin.net and it has the alias of mail.meibin.net rather than the host name of mail.meibin.net . Apache and loads of other software support virtual hosting and defining a name in an apache configuration has little to do with the actual underlying system hostname. That being said virtual hosts don't work well if DNS was not set correctly for them. HTH LukeK ___ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
