Bridging vs. Routing

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Message-ID: <7aavih$5ih$1@uuneo.neosoft.com>
References: <7a97jb$nio$1@news2.acs.oakland.edu> <36C8221C.A5121EF9@sco.deletethisbit.com> <F77EJx.H09@bilver.magicnet.netREMOVETHIS>

When you connect two networks, you have two basic choices: bridges or routers. If the networks are small, and the connection is not low speed, then a bridge makes sense because it just passes every bit of traffic to both sides: the bridge really joins the two networks together transparently.

But that strength is a weakness if the networks are large or the link between them is slow. I have used bridging over 56K when there was just one machine at one end and two or three at the other, but if you get much beyond that, you realy want to use a router. A router will only pass packets that actually need to be passed. That can introduce problems for Windows networks though. Windows browsing relies on broadcasting, and broadcasts are not passed across routers. That means that one side of the router can't see NetWork Neighborhood on the other, and vice versa.

There are a number of ways to solve this. Many modern routers specifically support sending netbios broadcast packets - the router looks for these and passes them to the other side. Machines can be configured to use LMHOSTS files which tell them the addresses of other machines: see Why can't my other sub-net browse the Visionfs or Samba shares? .

You will have a sample file (LMHOSTS.SAM) in \WINDOWS or for NT, it's "\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS" (assuming your system is in \WINNT)

Here's an example that happens to use an NT server for validation but the SCO server is running visionfs:

 
10.1.1.1        NTSERV1  #PRE    #DOM:THISDOM
10.1.1.1        "THISDOM        \0x1b"  #PRE
10.1.1.2        SCOSERV1        #PRE
 

Read the lmhosts.sam file carefully..spacing is critical on that 0x1b line.

You can also run a WINS server and point machines at that. It will track and update Network Neighborhood information for both sides. Your router may refer to ths with different phrases: "ip helper-address" on Cisco, for example. Individual machines may be pointed at WINS too.

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