Hello,
I seem to have developed network problem with one of my boxes. After a reboot yesterday I started having troubles connecting to it through the network. I experimented to try and find where the problem lay but all I can think of is a loopback problem. Here is what I tested:

1. The box can ping other sites in the big wide world as well as on the LAN.
2. The box cannot ping either its own IP address or is loopback address
3. I am not able to ping or connect (ssh etc.) to the box from another machine.

I have emptied all the rules from iptables and set all the defaults to allow, so it should not be a firewall problem. The only other thing I can think of is that it is a faulty network card, but this seems unlikely because some things work ok, and the NIC isn't concerned with the protocol either. But just to be safe, I moved the NIC away from the (old) graphics card.

BTW. The NIC is a Netgear

I may have also had the problem a while back when the machine was running a install of RH8. I say "may", because I was at Uni (box was at home) then and all I knew was that I couldn’t connect to the machine for long random periods (and nor could any other machine on the LAN).

Many thanks for any help!


Radam

PS. Oh, and i'm running Mandrake 10.0 Official. And before the fateful restart i installed sendmail, but that is now removed and the problem is still there.

Hello radam,

can you send screen of "ifconfig -a" command and "netstat -rn" of course hide your real ip address i suggested.


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lynOS

Hi,

The result of "ifconfig -a" is:
eth0 Link encap:Ethernet HWaddr 00:A0:CC:7B:3B:EB
inet addr:90.0.0.76 Bcast:255.255.255.255 Mask:255.255.255.0
inet6 addr: fe80::2a0:ccff:fe7b:3beb/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1082 errors:0 dropped:0 overruns:0 frame:0
TX packets:603 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:305831 (298.6 Kb) TX bytes:65928 (64.3 Kb)
Interrupt:10

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1025 errors:0 dropped:0 overruns:0 frame:0
TX packets:1025 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:85724 (83.7 Kb) TX bytes:85724 (83.7 Kb)

sit0 Link encap:IPv6-in-IPv4
NOARP MTU:1480 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)


And "netstat -rn":
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
90.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 90.0.0.1 128.0.0.0 UG 0 0 0 eth0
128.0.0.0 90.0.0.1 128.0.0.0 UG 0 0 0 eth0
0.0.0.0 90.0.0.1 0.0.0.0 UG 0 0 0 eth0



Thanks for your help!

Radam

PS. I left my IP in as it is internal to the LAN

It seems OK...

Type on the console

#ifdown eth0

than

#ifup eth0

after that try to access on another machine via ssh

(you can try to be sure iptables rule is empty " #iptables -F " to flush )

in other way is i think give another ip address on your network.

After that type

#service network restart

Thanks. I have given all of those a go and it does not seem to have helped. I also noticed that my /etc/hosts.deny file contains the single line (+ comments):
ALL:ALL EXCEPT 127.0.0.1ENY

I dont realy know how this file is layed out, but is this denying the loopback interface? Just a guess. I have never looked at this file before so I do now know if this is odd.

Also, /etc/hosts contains only:
127.0.0.1 localhost

The /etc/hosts.allow file is empty


I am barking up the wrong tree here? I'm not realy sure.

Thanks
Radam

OK

Take care

-------
lynOS

Hi,
I tried that and it doesn't seem to have helped :-(

I commented out the line in my hosts.deny file, rebooted and still had the same problem. I'm struggling to see what the problem is here, if anyone could point me in the right direction that would be great.

Also, what is the linux command for a traceroute?

Radam

It seems to be working now. Im guessing commenting that line helped. I checked on my other linux box and that line was not present. (Also, I must admit that I had not started sshd, which made connecting to it a little difficult!)

I dont know why that line was added to my hosts.deny file, its still a mystery. Actually, i still don't really know what the line means, if someone could tell me that would be great.

Thanks again


Radam

PS. I still cannot ping the loopback address, but I can make other connections on it. Considering that there is no firewall, isnt this a bit odd? Or could this be because the security level is set to "Higher"?