Host running FC4 is not pingable from other hosts

jge026 · 11-08-2005, 06:56 AM

I've got a network problem that I think (and hope) has a simple solution. I'm not a newbie to linux, but a newbie to troubleshooting networks since the distro network setups have always worked for me in the past. Thank you in advance for any help.

I have a Fedora Core 4 box which cannot be accessed from other computers on the local network. It doesn't respond to pings, ftp requests, ssh, smbmounts... etc. It connects to the internet just fine and can ping the other machines.

Here's what I know:
- Firewall is disabled.
- SELinux is disabled.
- I'm pinging by IP address, so it isn't a DNS problem
- The problem is NIC independent... same behavior on eth0 or ath0 (wireless card)
- The pings are actually reaching my computer (I can see them using ethereal) but it isn't responding to those pings.
- Once I ping another host, the other host is magically able to to recognize this computer, but only until that computer disconnects from the network (they're all laptops).
- Computer can ping itself just fine... not just 127.0.0.1, but 192.168.2.2 as well.

Unfortunately, this is a home desktop. I will not be able to respond to requests for more info except for mornings and evenings. Don't let that keep your from responding, though.

Thanks,
Justin

pingu · 11-08-2005, 07:16 AM

Very strange indeed...
And you are sure that SELinux is disabled, no iptables-rules blocking?
'cause it sounds like a firewall problem...

We need to know network setup, IP + netmask + gateway on troublecomputer and at least one more computer.
How are they connected? How do they get their IP's?
One idea is to check IP on all computers, maybe there's a duplicate?
Also check mac-adress, in rare cases you might have duplicates.

jge026 · 11-08-2005, 07:52 AM

Well, I'm sure I have SELinux & Firewalls disabled from the security level GUI. Here the output of iptables:

Code:

[root@hooloovoo ~]# iptables -nvL
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination    

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination    

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination    
[root@hooloovoo ~]# iptables -nvL -t nat
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination    

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination    

Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination

How could I convince you that SELinux is disabled?

Here is the output of ifconfig on this host:

Code:

inet addr:192.168.2.2  Bcast:192.168.2.255  Mask:255.255.255.0

And on the router

Code:

inet addr:192.168.2.1 Subnet mask: 255.255.255.0

I don't have access to another host, at the moment... I will tonight.
They all obtain their IP's through DHCP on the router. No duplicate IP's or MAC addresses.

pingu · 11-08-2005, 08:15 AM

The other computers might be more interresting, your FC4 contacts other computeres just fine, right? But it could be if you accidentally have two default gateways set in FC4.
Are the other computers Windows or Linux?
Are they all on same network?
Is the gateway set from router?
Also check the routing-table, "netstat -r" (should work in both Windows and Linux).

jge026 · 11-08-2005, 08:42 AM

Quote:

The other computers might be more interresting, your FC4 contacts other computeres just fine, right? But it could be if you accidentally have two default gateways set in FC4.

I will get you the other computers when I get home tonight. The other computers are all happily networked to eachother.
How would I set 2 default gateways in FC4? How would I check this, because I only see 1 in ifconfig?

Quote:

Are the other computers Windows or Linux?

There is a dual-boot XP & FC3 laptop, a Mac OSX laptop, and a TIVO.

Quote:

Are they all on same network?

yes. They all get their IP addresses through DHCP on the same router.

Quote:

Is the gateway set from router?

As far as I know.... since everything (including the router) has the same gateway.

jge026 · 11-08-2005, 09:22 PM

here is the network info of another host on the system.

Code:

inet 192.168.2.3 netmask 0xffffff00 broadcast 192.168.2.255

I think this checks out.

pingu · 11-10-2005, 09:23 AM

I don't know really...
Check the routing-table on FC4 with "route"
That's all I can think of for now?