From jensen@cc.gatech.edu Wed Sep 6 17:09:37 2000 Date: Tue, 5 Sep 2000 02:44:58 -0500 From: Peter Jensen To: jon@arctangent.net, leverich@photodex.com Subject: [peter@angband.org: (fwd) basic ip masq question] You'll should appreciate this. I hope this guy never gets a sysadmin job, even for the point of sale systems at McDonald's. At least he knows he's asking an obvious question. -Peter From: Tony Cha Newsgroups: git.unix.linux Subject: basic ip masq question Date: Tue, 05 Sep 2000 01:40:28 -0400 Organization: Georgia Institute of Technology, Atlanta GA, USA Lines: 28 Message-ID: <39B4874C.EE393831@prism.gatech.edu> NNTP-Posting-Host: unknown@r33h203.res.gatech.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news-int.gatech.edu 968132325 29487 128.61.33.203 (5 Sep 2000 05:38:45 GMT) X-Complaints-To: usenet@news.gatech.edu NNTP-Posting-Date: 5 Sep 2000 05:38:45 GMT X-Mailer: Mozilla 4.75 [en] (Win98; U) X-Accept-Language: en Xref: GT-News git.unix.linux:17642 1. This is so basic that I can't even find it in the HOWTO. :) If I want to ip-masq N machines off of the main gateway, do I need N + 1 ethernet cards on the gateway? One card for each machine plus one for the gateway itself? Or are there special cards which have multiple out jacks? 2. This is a direct quote from the HOWTO: > SLIP/PPP +------------+ +-------------+ > to ISP provider | Linux | SLIP/PPP | Anybox | > <---------- modem1| #1 |modem2 ----------- modem3| | > 111.222.121.212 | | 192.168.0.100 | | > +------------+ +-------------+ > o When a packet comes into the Linux box from ANYBOX, it will assign it > a new TCP/IP source port number and slap its own IP address in the packet > header, saving the originals. The MASQ server will then send the modified > packet out over the SLIP/PPP interface to the Internet. > o When a packet returns from the Internet to the Linux box, Linux examines > if the port number is one of those ports that was assigned above. If so, the > MASQ server will get the original port and IP address, put them back in the > returned packet header, and send the packet to ANYBOX. I guess my question is about this magical 'port number'. Does the 'Internet' not care what this port number actually is, if the Linux box can send whatever port number that it wishes to send? If the internet doesn't care, then what's the purpose of having a port number? Thanks. Tony