Nat ping PC on Internal Network

steve_roach · #1 27th December 2005, 04:31 AM

Hi,

I've been bashing away at this for a couple of days now and I've run right out of ideas.

History:

My server used to run Redhat 7.3 without any problems. I upgraded to FC4 and had all sorts of hardware problems cumulating in a new motherboard, PSU and, while they were in there, extra memory to bring it up to 1GB in total. I have a D-Link ethernet card and the motherborad has another ethernet on it (SiS900).

Network:

My Network (for the purposes of isolating this problem) looks like:

Linux Box Windows Box
lisa <-------hub------> homer
192.168.0.2 192.168.0.3

Configuration:

# ifconfig

eth0 Link encap:Ethernet HWaddr 00:0D:88:32:06:4A
inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::20d:88ff:fe32:64a/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:157 errors:0 dropped:0 overruns:0 frame:0
TX packets:108 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:16108 (15.7 KiB) TX bytes:7360 (7.1 KiB)
Interrupt:10 Base address:0xe800

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:2033 errors:0 dropped:0 overruns:0 frame:0
TX packets:2033 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1657756 (1.5 MiB) TX bytes:1657756 (1.5 MiB)

# netstat -nr

Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0

I have configured both ethernet cards in-turn to the same state and get the same problem, vis:

I can't ping the PC on the internal network by IP address.

I would appreciate any advice at all on this.

Regards

Steve

mndar · #2 27th December 2005, 04:42 AM

Have you configured the firewalls in such a fashion that they do not allow ping replies ?

steve_roach · #3 27th December 2005, 05:09 AM

Yeah, I think so.

On the Linux side:

# iptables -L
Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

# service iptables status
Firewall is stopped.

On the PC, I have both the Windows Firewall (stopped) and McAfee (stopped).

Still can't ping by IP address.

TIA.

funchords · #4 27th December 2005, 05:40 AM

Quote:

Originally Posted by steve_roach

Hi,

I've been bashing away at this for a couple of days now and I've run right out of ideas.

History:

My server used to run Redhat 7.3 without any problems. I upgraded to FC4 and had all sorts of hardware problems cumulating in a new motherboard, PSU and, while they were in there, extra memory to bring it up to 1GB in total. I have a D-Link ethernet card and the motherborad has another ethernet on it (SiS900).

Network:

My Network (for the purposes of isolating this problem) looks like:

Linux Box Windows Box
lisa <-------hub------> homer
192.168.0.2 192.168.0.3

Configuration:

# ifconfig

eth0 Link encap:Ethernet HWaddr 00:0D:88:32:06:4A
inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::20d:88ff:fe32:64a/64 Scope:Link
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:157 errors:0 dropped:0 overruns:0 frame:0
TX packets:108 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:16108 (15.7 KiB) TX bytes:7360 (7.1 KiB)
Interrupt:10 Base address:0xe800

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:2033 errors:0 dropped:0 overruns:0 frame:0
TX packets:2033 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1657756 (1.5 MiB) TX bytes:1657756 (1.5 MiB)

# netstat -nr

Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0

I have configured both ethernet cards in-turn to the same state and get the same problem, vis:

I can't ping the PC on the internal network by IP address.

I would appreciate any advice at all on this.

Regards

Steve

Try adding this line to /etc/sysconfig/network:

GATEWAY=<gateway IP>

steve_roach · #5 27th December 2005, 07:33 AM

Hi,

Thanks for that. I tried it and I still can't ping the PC.

I thought that the GATEWAY had something to do with the external connection, rather than the internal network.

Anyway, I added 'GATEWAY=192.168.0.2' to /etc/sysconfig/network. This IP is the address of the only network card that is configured. The otherone - the one I would usually connect to the ADSL modem - is currently off and unconnected.

Now I have:

# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
0.0.0.0 192.168.0.2 0.0.0.0 UG 0 0 0 eth0

Incidentally, ping returns this:

# ping 192.168.0.3
PING 192.168.0.3 (192.168.0.3) 56(84) bytes of data.
From 192.168.0.2 icmp_seq=1 Destination Host Unreachable
From 192.168.0.2 icmp_seq=2 Destination Host Unreachable
From 192.168.0.2 icmp_seq=3 Destination Host Unreachable

--- 192.168.0.3 ping statistics ---
5 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3999ms
, pipe 4

And tcpdump, during this time, returned:

# tcpdump -i eth0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
18:23:56.954649 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:23:57.954497 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:23:58.954345 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:24:00.955041 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:24:01.154093 IP lisa.steveroach.org.5353 > 224.0.0.251.5353: 0*- [0q] 2/0/0 (Cache flush) A lisa.steveroach.org, (76)
18:24:01.156010 arp who-has 68.87.66.196 tell lisa.steveroach.org
18:24:01.954891 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:24:02.155859 arp who-has 68.87.66.196 tell lisa.steveroach.org
18:24:02.954737 arp who-has homer.steveroach.org tell lisa.steveroach.org
18:24:03.155707 arp who-has 68.87.66.196 tell lisa.steveroach.org
18:24:03.157697 arp who-has 68.87.64.196 tell lisa.steveroach.org

Thanks for your continuing help.

funchords · #6 27th December 2005, 08:24 AM

Yeah, sorry for that. I'm not used to the *nix flavor of routing tables. Please reverse that change that you made.

I noticed that your ifconfig does not have the RUNNING flag for eth0 (compare to lo). My cursory search seems to indicate that the RUNNING flag means that the device is connected. The UP state means that the interface is UP. The user/app/OS controls the UP flag. The driver/hardware controls the RUNNING flag.

My groups.google.com search terms were (with the quotes): ifconfig "RUNNING flag"

This suggests a bad cable or connection, but I get that suggestion only from doing that searching and reading...

I hope I did better by you this time. :-)

steve_roach · #7 27th December 2005, 11:47 AM

> Yeah, sorry for that. I'm not used to the *nix flavor of routing tables. Please reverse that
> change that you made.

No problem. Everything is useful right now.

> I noticed that your ifconfig does not have the RUNNING flag for eth0 (compare to lo). My
> cursory search seems to indicate that the RUNNING flag means that the device is
> connected. The UP state means that the interface is UP. The user/app/OS controls the UP
> flag. The driver/hardware controls the RUNNING flag.

>My groups.google.com search terms were (with the quotes): ifconfig "RUNNING flag"

Yeah, I did a search and came up with the same thing.

> This suggests a bad cable or connection, but I get that suggestion only from doing that
> searching and reading...

Yeah, I checked the connections and it looks like one of the cables was loose. Sadly, that hasn't fixed it!!!

My ifconfig is now:

# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0D:88:32:06:4A
inet addr:192.168.0.2 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::20d:88ff:fe32:64a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:2240 (2.1 KiB)
Interrupt:10 Base address:0xe800

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:1382 errors:0 dropped:0 overruns:0 frame:0
TX packets:1382 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1800890 (1.7 MiB) TX bytes:1800890 (1.7 MiB)

However, I'm still a bit suspicious of the hardware. Think I'll knock up a new crossover cable and see how that goes.

I'll get back.

> I hope I did better by you this time. :-)

LOL, yeah, thanks.

steve_roach · #8 27th December 2005, 12:12 PM

Dunno how to thank you guys - you are stars.

I made up a new crossover cable and...perfect. I can ping to my heart's desire. That certainly gets me back on the road and I can get on and install the rest of the server.

Over the next few days, I'll check out the suspicious stuff - which right now looks like either one of my standard cables or the hub.

I'll post the results when they're in.

Once again, thanks to all. Oh, and a happy new year.

Regards

Steve