nmbd & netbios name -> many addreses

Luke Kenneth Casson Leighton lkcl at switchboard.net
Fri Mar 12 01:08:48 GMT 1999

On Fri, 12 Mar 1999, Christopher R. Hertel wrote:

> > 
> > Christopher R. Hertel wrote:
> > > It makes sense that a multi-homed host would register multiple IPs per
> > > unique name.  The name represents a service, and NetBIOS is only being
> > > emulated over TCP/IP.  So, the Service exists on multiple emulated
> > > NetBIOS networks, all sharing a single WINS server.  Uhhhrrgh.
> > 
> > 	Yup: the semantic gap is rather gaping here (:-))
> > 	However, if the client makes the PC assumption that
> > 	it's on a single LAN, and that it only could have one
> > 	address, it's only going to try registering what it
> > 	thinks is it's primary address.
> The line between the NetBIOS LAN and the TCP/IP network(s) is easy to
> blurr.

why?  both are independent transports: one is proxied over the other.

> The RFCs describe a means of emulating


> a NetBIOS LAN (emphasize LAN) over 
> TCP/IP.  The emulated LAN exists over the union of the IP Broadcast 
> domain and the set of systems sharing the same NBNS.
> NetBIOS itself doesn't know or need to know anything about multiple
> interfaces.  The IP layer handles that.  The NetBIOS layer only knows (and
> only needs to know) about the NetBIOS names (i.e., NetBIOS services and
> clients) it can reach. 

and because of this you can have multiple NetBIOS services and NetBIOS
clients running on *any* host *including* the same host (with any
arbitrary number of ip addresses on each and every host involved, as long
as they run tcp/ip AND they run NetBIOS over tcp/ip).
> > 	A very smart smb server, knowing it was on a multihosted machine,
> > 	might arrange to register itself with an equivalently smart wins
> > 	server on multiple interfaces, so we might arrange to support but
> > 	not require such behavior, and plan on making Samba smarter...
> The real key when it comes to multi-homed hosts is routing.  If you have
> an SMB server which is multi-homed, you want your clients to get the IP
> address of the server interface which is "closest" (in hops and cost) to
> them. 

broken clients (e.g wfwg) are supposed to be capable of taking _just_ the
first name in a multi-homed response and ignoring all other ip addresses.
which is why the sort is required: to minimise routing.

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