TCP/IP, Gateway addr, Masks, etc.

[txjailer_SCS 0]

I get by in setting up a simple network using one gateway and router. When it gets to the point of changing the masks, joining two different gateway networks, etc. I'm lost. Tried to look at books on network basics, they start out simple but suddenly go into the guts of inter-networking which is too abrupt for me. Can anyone recommend a good source on describing the basics of TCP/IP networking that will go from simple networks to inter-networking using switches, multiple routers, etc. showing how to use those parameters properly written in a straightforward manner going from A to B to C without the A to G to Z as I've encountered in books. Thanks in advance!!! Shawn

[Crossbow 297]

Basically the difference is connecting multiple networks is simple. Computers who are not part of the same subnet cannot see each other without a router. That's the default gateway setting on the units. If it cannot find an IP address in it's local address, it will direct that traffic to the default gateway. The gateway is the device which needs to have a routing table that explains who it needs to talk to for tranmitting to the other networks. Say PC 1 is 192.168.0.10. Say PC 2 is 192.168.1.10. PC 1's default gateway (typically 192.168.0.1) would have a table entry that told it how it is supposed to forward packets to the 192.168.1.x network. PC 2's default gateway would tell that network how to talk to the 192.168.0.x network.

[Nathan 7]

Crossbow's basic explanation of routing is good. Check out subnet masks to determine which computers are on the same network. The subnet mask is a way to define which nodes are on the same "subnet" (network segment). The entire address is 32 bits long and the mask tells how many bits identify the network versus how many bits identify the node on the network. The Class C (255.255.255.0) subnet that Crossbow mentioned has only 2^8 (255) addresses, but has 2^24 different networks. So, 192.168.0.x is on a different subnet than 192.168.1.x. This is where the default gateway comes in. I've posted similar content here (it also describes non-routable addresses): I'd recommend that you first learn how subnet masks work, then basic routing. After that check out the basics of DNS and ports. You'll be able to troubleshoot a TCP/IP network after that. It it will then be easy to get into fancy subnet schemes, bridges versus routers, NAT, VPNs, etc. I've been meaning to write a "TCP/IP networking for Integrators" guide that's simple and covers these types of questions. I'd be happy to answer more specific questions. Edited 27 Feb 2007 by Nathan

[Crossbow 297]

I read and reviewed a pocket reference guide for Industrial Ethernet years ago. Author was Perry S. Marshall, published by the ISA, and the name of the book was 'Industrial Ethernet, a pocket guide'. It had a great deal of information on Ethernet and PLCs. Might want to check it out... Second edition is available via www.amazon.com for around $55 US.

[P Daniil 0]

The IBM Redbook "TCP/IP Tutorial and Technical Overview" may help you as reference material. You can download it (pdf format, 7.5 MB) from the IBM Redbook site here