Destination Host Unreachable....Network Setup

[matpoh]

I am in the process of setting up the network card on my dual boot RedHat 8 machine and am at a loss.

I am using DEC 21040 ethernet card that can ping itself, but cannot ping anything else. I know its not the cable or port because everything works fine on the windows side (go figure)

Anyway, here is the output of my ifcfg_eth0

Device=eth0
bootproto=none
broadcast=*.*.223.255
ipaddr=*.*.223.105
netmask=255.255.255.0
network=*.*.223.0
onboot=yes
userauth=no
peerdns=no
gateway=*.*.223.254
type=ethernet


-My dns server is *.*.226.1
-My ethernet card is using irq 11 and is not sharing with anything else.
-I think the driver my card is using is something called Tulip


Any suggestions are greatly appreciated

[bwkaz]

OK, your netmask is /24 (basically). But your DNS server is therefore on a different subnet than your machine... try moving it onto the correct subnet first.

If that doesn't help, then what, exactly, are you doing, and what, exactly, is it telling you? For example, "I type ping *.*.223.1 and it says ping: Destination net unreachable" would be the kind of thing I'm looking for.

[matpoh]

Yes, I am on a different subnet than the dns server. When you say to move the machine to the correct subnet, are you saying to use a netmask of 255.255.0.0?

When I ping anything except the card itself, I get....
pinging from *.*.223.105........Destination host unreachable....


When you say the netmask is /24 what are you saying?

[ask_123]

"ping:destination host unreachable" means there is no route to the destination. Either your network services is not enabled or the routing table does not have a route to the specific host.

run "route" and check the routing tables

[bwkaz]

/24 is the CIDR notation for a netmask where the top 24 bits are 1, and the rest are 0. In other words, 255.255.255.0, like you said.

When I said put the DNS server on the same subnet, I meant change the IP address of the DNS server so that its first 3 octets (the first 3 numbers) match the address of the other machines that are trying to talk to it. Or is there a router between you and the DNS server? Because that would work too; then you shouldn't have to change anything.

As for the problem, yeah, check the routing tables. And double-check the network cabling. ;)

[cowanrl]

Usually you get the "destination host unreachable" when you try to ping an address on the same subnet as your machine and your machine doesn't get a response to it's ARP request.
The "destination net unreachable" message indicates that no route can be found to the remote network. This can be generated by your local machine or by a router somewhere along the way, often the default gateway.

Make sure you have a link light on both your NIC and the hub/switch the computer is plugged in to.
If the NIC or hub/switch have an activity light on them, try to watch for it to flash as the ping packets are sent out. This is not always possible on a busy network but can be helpful if there's not much traffic on the network. If the activity lights don't flash, your packets aren't being tranmitted.

After you do the ping and get no response, execute "arp -n" to see if there's an entry in your arp table for the host you are trying to ping.
If there's not, you probably aren't transmitting packets at all, especially if other machines on the network can ping the same machine.
If there is an entry in the ARP table for the machine you tried to ping, then you are able to send broadcasts but not unicast traffic. I'd look for a firewall somewhere that is so restrictive that it won't even let pings through.

More than likely you won't have an entry in the ARP table. Execute mii-tool. This should return the state of your ethernet connection, something like:

eth0: negotiated 100baseTx-FD flow-control, link ok

If it doesn't say link OK then you have no physical connectivity. Since you know the NIC and cable are good, there's some kind of problem in Linux.
Sometimes it may be as simple as setting to NO an option in the BIOS that indicates whether you are using a PnP OS. Sometimes you may need to change your NIC driver, either to a newer or an older version.
Until you can get your physical layer up and working, you'll never be able to ping.

[yinrunning]

when you say you're pinging the card, does that mean you're pinging 127.0.0.1, or the actual address of the card? Try both if you haven't.

Also, this was written for a dhcp setup, and it doesn't include any of the dns stuff, but check the files mentioned anyway:

http://cloud.prohosting.com/redllama/rhHOWTO1.html

Just keep in mind that you're using static IP's, not dynamic.

And if
$ ifconfig
doesn't have a section for eth0, then your card is NOT up.

[cowanrl]

One thing to remember about the output of ifconfig. When it says UP, all it means is that software has loaded successfully and that protocols, such as TCP/IP, have been bound to the interface successfully. It does not mean that the interface is physically up. You need to use mii-tool to see the physical state of the interface.

You can unplug your cable from the NIC and ifconfig will still show the interface UP. It will respond to pings to itself. However, mii-tool will show the interface physically down.

[yinrunning]

cool. I didn't know that.

[chrism01]

some good info there. Might I also suggest using 'traceroute'? It'll tell you how far through your networks you are getting before it fails to reach the final destination.