Local network & SLIP

Local network & SLIP

Post by Patrick Vestje » Wed, 12 Jul 1995 04:00:00



Hello there,

since a few days I'm the lucky owner of two NE2000 comp. ethernet cards that
I use to connect two PC's using a LAN. In order to be able to communicate
over the LAN, I have to assign network addresses to the computers. I
understand that I can choose these network addresses quite arbitrary as long
as I don't 'let them go outside'.

However, sometimes I make a SLIP connection to the university I'm working
for. Since it's a dynamic SLIP connection, most of the time I get a
different network address for the machine I make the SLIP connection with.

Now, how do I setup Linux properly so that I can use both the LAN and the
SLIP connection at the same time? Do I have to apply for official network
addresses (but then what about the address assigned during the SLIP
connection)? Or do I have to play one of the computers the role of gateway?
Or ...

Any help would be greatly appreciated,

regards, Patrick.

 
 
 

Local network & SLIP

Post by <shar.. » Wed, 12 Jul 1995 04:00:00



Quote:>. . . connect two PC's using a LAN. . . .
>I have to assign network addresses to the computers.

Not quite. Technically, each net interface has an IP address.
A computer with two interfaces has two IP addresses.

Your modem counts as a net interface. It's IP address is assigned by
the Internet service provider you connect to.

Quote:>I understand that I can choose these network addresses quite
>arbitrary as long as I don't 'let them go outside'.

No you can't! There are specific network numbers reserved for
this purpose. Use those. Details in the Internet standards
documents called RFCs. Those are FTPable somewhere. I think
is.internic.net.

Quote:>However, sometimes I make a SLIP connection to the university I'm working
>for. Since it's a dynamic SLIP connection, most of the time I get a
>different network address for the machine I make the SLIP connection with.

They own the "net" on the modem connection side, so they assign
addresses there. If they do that dynamically, then you need to
discover at connect time the IP addresses they've assigned for
*two* modems, yours & theirs, and put this info into Linux's
routing tables.

Quote:>Now, how do I setup Linux properly so that I can use both the LAN and the
>SLIP connection at the same time? Do I have to apply for official network
>addresses (but then what about the address assigned during the SLIP
>connection)? Or do I have to play one of the computers the role of gateway?

Yes, if it's got two interfaces on two nets then it's a gateway.
You have to set up the ARP tables on the gateway machine so it routes
to your other PC via the Ethernet & to anything else via SLIP. Any
other machine on your net just gives the gateway any packets it has
for anything off your net.

 --
 Sandy Harris


 
 
 

Local network & SLIP

Post by Matthew Crav » Thu, 13 Jul 1995 04:00:00




>>I understand that I can choose these network addresses quite
>>arbitrary as long as I don't 'let them go outside'.

>No you can't! There are specific network numbers reserved for
>this purpose. Use those. Details in the Internet standards

These are detailed in RFC 1597, "Address Allocation for Private
Internets". In summary, the ranges of addresses available for this
purpose are as follows:

           the Class A address block    10.0.0.0
           the Class B address blocks   172.16.0.0  through 172.31.0.0
           the Class C address blocks   192.168.0.0 through 192.168.255.0

The Linux Network Administrator's Guide notes that if you are using a
private internal network and need subnetting, it may be to your
advantage to use one of the reserved Class B address blocks, since
this makes subnetting more intuitive (the 3rd octet becomes the
subnet, rather than using the high bits of the 4th octet of a class C
address.)

/MC

--
--
Matthew Cravit, UPIT-ATD           |  "After all is said and done,
DePaul University, Chicago IL      |   more is said than done."

 
 
 

1. local network using SLIP

Hi,

sorry if this is mentioned somewhere, bit i didn't find it in the FAQs
(if it is, just point me to the appropriate FAQ)...

i have access to 2 machines (not connected to the net) and i would
like to set up a local network between the 2 machines using SLIP and a
null-modem cable. is this possible with the current SLIP release?

the FAQs explain how to connect to a SLIP server via modem but not how
to set one up. i suppose that's what i'll have to do (one machine as a
slip server and the other connecting with dip on the serial port to
establish the net link).

thanks in advance
Massimo
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