LAN sending data over WAN with switch

J

jaguarfox13

Registered
i dont think the actual configuration will make any difference, but thought i'd mention it anyway:
Imac G3/500
Powerbook G4/667
Cisco Cable Modem
3com 5 port switch
Each of the two macs get their IP-Addresses from the dhcp of my ISP.

Now the problem:
Connecting from one machine to the other (using the others ip. afp or whatever protocol else), data is not sent:
PB G4 --> switch --> IMac
but:
PB G4 --> switch --> cablemodem --> ISP --> cablemodem --> switch --> IMac
So all the data goes out to the ISP and back. On a 512/128k cable connection this is kinda a problem. :)
any idea how to fix that (without buying a router)?
 
What do you mean when you say that "data is not sent" between the PB and iMac. Is the cable modem off and now they can't see each other? Did you just disconnect the cable modem?

I'm assuming you have the two computers plugged into one switch that also has the cable modem hanging off of it. And that both computers use dhcp to get their ip addresses from your isp?

If this is the case, then if you're not connected to your isp, and have no local dhcp server running, your problem would simply be that your computers have no ip address and therefore can't communicate with the presence of your isp.
 
Apparently i didn't make myself clear...
Originally posted by binaryDigit
computers plugged into one switch that also has the cable modem hanging off of it. And that both computers use dhcp to get their ip addresses from your isp?
Click to expand...
thats completely right. The problem as i tried to describe, is, that all the data sent from one mac to the other, does not travel from mac1 over the switch to mac2; but from mac1 over the switch to the ISP and then back over the modem and switch to mac2.
the problem is actually the absence of a router that would make a "real" local network and redirecting the data packets directly from mac1 to mac2.

everything's clear now? just ask....
 
OK, I see. Are both computers getting ip addresses on the same subnet (i.e. they both have the same first three numbers of their ip addresses 99.199.99.XX). If not, then you'll need to explicitly add an entry into your routing tables so that any traffic destined to the other computer goes directly there. I'm not in front of my mac right now so I can't tell you exactly what to do, but take a look at the 'route' command (man route). This should make things work.

BTW, are you determining that your traffic takes this circuitous route by running traceroute?
 
They are NOT in the same subnet. otherwise it would work , maybe....

never heard of that route command. but i'll check it out as soon as i've got the time! hopefully i know how to use it...
yes i found out about that by running a traceroute (and because of the slow speeds).

Many thanks for the help...
 
Sure...

sudo route add -host <destination>/32 <gateway>

Where the remote machine's ip addy is the destination, and your ip addy is the gateway.

For example:

sudo route add -host 10.0.0.4/32 192.68.1.7

However, if they're on different subnets, I don't think it'll work. As others have noted, if they were on the same subnet, this wouldn't be a problem.

IMO, the NAT/FW/router would be the best solution here. I personally wouldn't be hanging machines directly on the internet like that anyway. Just my $0.02... :)
 
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