pc/linux tcp/ip problems..

David Johnson dgj-dave at pacbell.net
Sun Jan 23 23:06:01 PST 2000

    Well all has been solved! all I had to do is add the two networked machines
ips to the route table per your directions and VOILA! everything pings great
and as well Masquerading is up and operating (less than 15 minutes ater your
Thanks again You saved me a few Tylenols :)
-David Johnson

ME wrote:

> Here is the first suggestion:
> Log into the Linux box as root.
> type "ifconfig eth0" and look at the information. Does the information
> describe the IP address that that Ethernet card should have? (IP Address
> netmask, broadcast address, etc for ITS network.)
> type "ifconfig eth1" and look at the information. Does the information
> describe the IP address that that Ethernet card should have? (IP Address,
> netmask, broadcast address, etc for ITS network.)
> If both of these are "yes, then continue. If NO, then send another e-mail
> with your findings or resolve the inconsistancies on your own.
> When you log into the linux box, can you ping the IP addresses that match
> either of the two Windows boxes? (, or
> If Yes, then jump down below to "SMB/NMB:"
> If No, then read here:
> As root, login to you Linux box and type "route"
> (or "route -N" if you are not connected to your ISP at the time)
> Examine your routing list.
> You should have something which may look like this (if we assume that eth0
> is your primary Ethernet interface to your ISP over DSL, and eth1 is the
> Ethernet link to your LAN.)
> YourMachineName:~# route -N
> Kernel IP routing table
> Destination     Gateway      Genmask         Flags Metric Ref    Use Iface
> ISP.ASSIGN.IP.A UH    0      0        0 eth0
> UH    0      0        4 eth1
>   U     0      0        4 eth1
>       U     0      0       16 lo
>         ISP.ASN.GW.A         UG    1      0     7470 eth0
> Where "ISP.ASSIGN.IP.A" would be the IP address given to you by your ISP
> and "ISP.ASN.GW.A" would be the default gateway they gave you. (I am
> assuming you only have 1 IP address from your ISP)
> If you do not have a local route letting your linux box know that it is
> to deal with the "192.168.0.X" network through eth1, then it may try to
> reach the "192.168.0.X" by using the default route (see the first left
> hand column that has the last entry with "") and send it out eth0
> to your ISP, which will promptly drop the packets since they are part of
> the reserved class of IP addresses.
> If you have a routing table that tells your kernel how to contact the IP
> addresses that are part of the "192.168.0.x" network, and they still do
> not respond to pings from your Linux box shell, then we can try adding
> static routes to see if that helps, even though it is not likely to help at
> all.
> For static routes, at the linux box as root try:
> route add -host dev eth1
> route add -host dev eth1
> Then try to ping these IP addresses again. Does it work?
> No? Send another e-mail to the list including a dum of the "route -N" and
> "ifconfig eth0" and "ifconfig eth1"
> If so, try to ping your linux box from the DOS machines, and if that does
> not work, then proceed to "SMB/NMB:"
> Here is another guess:
> Windows machines are able to exchange some networking formation about
> each other using SMB/NMB.
> Also, they often attempt to use Name Resolution using the local hosts
> file, then look at the names discovered via the local cached Domain
> Controller or Master Domain Browser.
> If none of the above work, then they try a WINS,
> If WINS fails, then they resort to DNS.
> (My memory is a bit fuzzy on the order, and procedure listed above, so
> someone else can feel free to correct me.)
> I have had times where even entering just an IP address to ping from a
> Windows 95/98 machine, I get no responses appearing when the DNS is not
> available. (I have not examined this in detail, but would guess that it
> even asks a DNS what IP address the IP address given to them is.)
> See if you can locate a "hosts.*" or "lmhosts.*" file in your
> c:\Windows or c:\windows\system folders. (I do not recall the extensions.)
> In this file, create a temporary entry like "gateway1" to map to the ip
> address of your linux gateway.
> Reboot the machine, and look through the network neighborhood and make
> sure you can see the other windows box.
> When you can see the other windows box in the network neighborhood, then
> try going to a DOS-box and:
> ping gateway1
> See if this offers responses.
> If after all of the above you are still in no-where-vile, send us
> another e-mail with more routing and interface data.
> After you are able to have all three machines ping each other, then the
> next step would be to set up the IP Masquerading. :-)
> (once your can have all 3 machines ping each other, you wouldn't be able to
> ping "outside" Internet machines until IP Masquerading is set up. Your
> e-mail is well documented in what you have tried, so I strong suspect you
> know this, but state it "just in case" you do not.)
> > -Is there something I am completely overlooking?
> > I'm very familiar with networking on pcs and trying to learn the linux
> > platform so any suggestions would be of great help.
> > p.s. I am currently reading the how-to's but it is a slow process. ;)
> > Thank You for any help
> > David Johnson
> Your e-mail is well documented, and you have provided an excellent list of
> things attempted. The verbose nature of this e-mail is not entirely meant
> for your use, but for other on the list that may not be as skilled as you
> in networking.
> Good question!
> -ME
> P.S. Confirmation of the actual solution is useful for future problems
> encountered by others and allows me to sleep better at night.

More information about the talk mailing list