Accessing other machines on same router

moonmoth · 07-22-2005, 11:02 AM

I found a few threads that hit all around my problem, but none right on point. So will go ahead and ask it, even though I feel sure it has been asked before. I have several machines, all connected to a router, which is in turn connected to a cable modem. Some machines run only Windows XP, while others can run either Windows XP or Linux. I have Fedora Core 4 on this machine and RH9 on two of the other machines. All machines, both with Windows and Linux, are set up to obtain an IP address from the router, using DHCP. (I presume that it would be correct to say the router acts as a DHCP server). The router is IP address 192.168.1.1, and assigns IP addresses to the machines in the range 192.168.1.100 on up. Everything works fine, all machines can connect to the Internet. The Windows machine can exchange files (I used the Network Wizard to set them up). But Linux is another story. No Linux machine can ping or otherwise connect to any other Linux machine using hostname. (For simplicity, I'll confine the rest of this to only two Linux machines.) Doing /sbin/ifconfig gives me the IP address that the router assigned (only when they logged into the Internet, though) and other presumably good stuff. I can ping each from the other, using that IP address. But I cannot ping using the hostname. Now, I fully realize that life is a lot simplier using static IP addresses. But my router is set up for DHCP, and although in theory that can be changed, in practice if I try to change it and mess up my wife's access to the Internet then I am in deep trouble! So I'd prefer to stay with DHCP. Given that, how can I solve the problem. (The problem is not really being unable to ping -- I need to set up file sharing using NFS and am going to have to use host names to do that).

Matir · 07-22-2005, 11:56 AM

Do 'route' and post the output. However, I think I may know the problem.
My route output looks like:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     *               255.255.255.0   U     0      0        0 eth0
loopback        localhost       255.0.0.0       UG    0      0        0 lo
default         192.168.0.1     0.0.0.0         UG    0      0        0 eth0

(Obviously, my network uses the 192.168.0.0/255.255.255.0 network, so substitue a .1 for my .0 in the 3rd position)

If you lack the line that starts with a network address (in my case, 192.168.0.0), you probably need:

Code:

route add -net 192.168.1.0 netmask 255.255.255.0 dev eth0

Where eth0 is the interface connected to the router.

moonmoth · 07-22-2005, 01:03 PM

DESTINATION GATEWAY GENMASK FLAGS METIC REF USE IFACE

192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
Default 192.168.1.1 0.0.0.0 UG 0 0 0 eth0

Matir · 07-22-2005, 01:18 PM

You know, I completely misread part of your original post. Sorry.

How are hostnames set up? Do you just mean the hostname provided in /etc/hostname? You'd need a DNS server (or a dhcp server that provides DNS services) on the network to take advantage of name->ip mapping. (Or /etc/hosts files, but those require the IPs to be static)

moonmoth · 07-22-2005, 02:07 PM

Well, it was a long post. I should have broken it down into paragraphs, I supposed, to make it easier to read. :-)

Yes, I just used the hostname command to set up the hostname. (hostname xp.MSHOME, for example).

Matir · 07-22-2005, 02:10 PM

Just using the hostname command will not make it accessible to other computers by that name. The hostname command basically says "this is the name you should know yourself as." You still have to tell other computers what to call it by. Unfortunately, with DHCP from a router (assuming a 'thin' router: i.e., linksys) this is not so easy. With a linux router, you could just slap dnsmasq on there and be done.

moonmoth · 07-22-2005, 02:18 PM

Well, I'm going to try mixing static IP's and see what harm that does. That is, I will use the network configuration tool and add to the /etc/hosts file with that tool, static IP's (which I will just make up, in the range of 192.168.1.200 up). After all, there HAS to be a way to make it work with the router because Windows XP makes it work!

Matir · 07-22-2005, 02:22 PM

If you're going to use static ips in there, use them in a range that DHCP will never assign. For example, if you want to use 192.168.1.200+, then set the router to do DHCP on 192.168.1.100-192.168.1.199. If two computers do get the same IP (which is possible with less than 100 computers due to how most of those routers work), you will have no end of headaches until you pull the plug on one.

moonmoth · 07-22-2005, 02:40 PM

I only have five computers, and have noticed that the router always just starts at 192.168.1.100, then increments by 1, etc. So the highest IP ever assigned (from my observations so far) is 192.168.1.104. That is why I started the static IP addresses with 192.168.1.200, which should not cause any conflict. (I hope :-)

Matir · 07-22-2005, 02:44 PM

You *SHOULD* be okay, but I've seen a router that would go through it's whole available range before restarting, like so.

Computer 1 gets .100
Computer 2 gets .101
Computer 1 gets rebooted, receives .102
Computer 2 gets rebooted, receives .103
...
Computer 1 gets rebooted, receives .254
Computer 2 gets rebooted, receives .100