Unable to see apache2's web site from outside firewall-although from within its there. Yet forwarding appears ok..

Posted on 2005-03-10
Medium Priority
Last Modified: 2010-03-18
Hello experts,
>>> I have installed Mandrake Linux 10.1 including Apache2 .. My problem is that > From another machine on the same Local network I can bring up apache's default page browsing to its ip... Good - its working.

After configuring forwarding and NAT on that networks Firewall (Netmax5-serving several servers including new Apache server)from the outside world. I can not get to apache when using its assigned external ip address .. This should work..

To test if the forwarding is actually working >If I assign another machine (pc-IIS) the apache's internal i/p and swap their network cables-- It works.. I can open IIS web pages from outside. I am not the brightest but I have done this before on linux 9-9.2 with no real difficulty so what is wrong . I have rebuilt the whole thing twice now with no luck.

There are no traces of anything in httpd access or error logs. you can browse the world from the apache machines web client. No firewall is on on the Apache2 Linux machine - its security level currently set to poor..  I can ping apache's external i/p. I can ping from the firewall machine to the apache's internal i/p..

Any help much appreciated.
Question by:shlam
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Expert Comment

ID: 13505007
Try turning ip_filter off:
echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter

Author Comment

ID: 13505309
Hi Bob , Unfortunately No joy. was already  0 . thanx anyway

Expert Comment

ID: 13505741
Can you run tcpdump on the apache box while attempting access from the outside?  

That would confirm:
- that the packets are arriving at the server
- how the server is replying if the packets are there.

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Author Comment

ID: 13506146
Ok tried that... and got this ~
The machine from the outside is

AT the bottom I also accessed from a machine on same network (

listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
14:05:01.367213 IP > S 775591967:775591967(0) win 16384 <mss 1460,nop,nop,sackOK>
14:05:01.369621 IP > zebedee.magic.sound-effects-library.com.domain:  60573+ PTR? (40)
14:05:01.370150 IP zebedee.magic.sound-effects-library.com.domain >  60573 NXDomain* 0/1/0 (130)
14:05:01.370503 IP > zebedee.magic.sound-effects-library.com.domain:  60574+ PTR? (45)
14:05:01.370714 IP zebedee.magic.sound-effects-library.com.domain >  60574 ServFail 0/0/0 (45)
14:05:04.310686 IP > S 775591967:775591967(0) win 16384 <mss 1460,nop,nop,sackOK>
14:05:06.362613 arp who-has tell zebedee.magic.sound-effects-library.com
14:05:06.362647 arp reply is-at 00:03:47:08:49:40
14:05:10.345762 IP > S 775591967:775591967(0) win 16384 <mss 1460,nop,nop,sackOK>
14:05:10.372152 IP > zebedee.magic.sound-effects-library.com.domain:  60574+ PTR? (45)
14:05:10.372527 IP zebedee.magic.sound-effects-library.com.domain >  60574 ServFail 0/0/0 (45)
14:05:15.371055 arp who-has zebedee.magic.sound-effects-library.com tell
14:05:15.371157 arp reply zebedee.magic.sound-effects-library.com is-at 00:b0:d0:79:2e:e9
14:05:19.373763 IP > zebedee.magic.sound-effects-library.com.domain:  60575+ PTR? (40)
14:05:19.374264 IP zebedee.magic.sound-effects-library.com.domain >  60575* 1/1/1 PTR[|domain]
14:05:19.374772 IP > zebedee.magic.sound-effects-library.com.domain:  60576+ PTR? (41)
14:05:19.375045 IP zebedee.magic.sound-effects-library.com.domain >  60576 NXDomain* 0/1/0 (131)
14:05:19.375233 IP > zebedee.magic.sound-effects-library.com.domain:  60577+ PTR? (40)
14:05:19.375484 IP zebedee.magic.sound-effects-library.com.domain >  60577 NXDomain* 0/1/0 (130)
14:05:29.210248 IP zebedee.magic.sound-effects-library.com.52999 > S 2571827631:2571827631(0) win 5840 <mss 1460>
14:05:29.210319 IP > zebedee.magic.sound-effects-library.com.52999: S 1049582954:1049582954(0) ack 2571827632 win 5840 <mss 1460>
14:05:29.210444 IP zebedee.magic.sound-effects-library.com.52999 > . ack 1 win 5840
14:05:29.210674 IP zebedee.magic.sound-effects-library.com.52999 > P 1:410(409) ack 1 win 5840
14:05:29.210712 IP > zebedee.magic.sound-effects-library.com.52999: . ack 410 win 6432
14:05:29.214300 IP > zebedee.magic.sound-effects-library.com.52999: . 1:1461(1460) ack 410 win 6432
14:05:29.214328 IP > zebedee.magic.sound-effects-library.com.52999: P 1461:2632(1171) ack 410 win 6432
14:05:29.214702 IP zebedee.magic.sound-effects-library.com.52999 > . ack 1461 win 8760
14:05:29.214752 IP > zebedee.magic.sound-effects-library.com.52999: P 2632:3241(609) ack 410 win 6432
14:05:29.214814 IP > zebedee.magic.sound-effects-library.com.52999: . 3241:4701(1460) ack 410 win 6432
14:05:29.215193 IP zebedee.magic.sound-effects-library.com.52999 > . ack 2632 win 11680
14:05:29.215238 IP > zebedee.magic.sound-effects-library.com.52999: . 4701:6161(1460) ack 410 win 6432
14:05:29.215246 IP > zebedee.magic.sound-effects-library.com.52999: FP 6161:7316(1155) ack 410 win 6432
14:05:29.215214 IP zebedee.magic.sound-effects-library.com.52999 > . ack 3241 win 14600
14:05:29.215234 IP zebedee.magic.sound-effects-library.com.52999 > . ack 4701 win 17520
14:05:29.215596 IP zebedee.magic.sound-effects-library.com.52999 > . ack 6161 win 20440
14:05:29.216591 IP zebedee.magic.sound-effects-library.com.52999 > F 410:410(0) ack 7317 win 23360
14:05:29.216620 IP > zebedee.magic.sound-effects-library.com.52999: . ack 411 win 6432

40 packets captured
40 packets received by filter
0 packets dropped by kernel

I can see servFAIL in there

Author Comment

ID: 13506178
sorry the machine I used on the local network wasnt it was

Expert Comment

ID: 13506423
So the firewall is not the issue since the apache server never responds.

The apache server is and your local client/dns server is zebedee.magic.sound-effects-library.com or, right?

The servFAIL is on a reverse DNS lookup for the external IP address.

Since it does this before responding to the http request, I think the apache config is telling it to do reverse DNS (probably for logging purposes) and set to not respond if it can't resolve the IP to a name or to only allow access from certain domains.  

It's been a while since I've played with Apache configs, but look in your httpd.conf for mod_access directives or the HostnameLookups directive.  Try setting the HostnameLookups to off.

Author Comment

ID: 13506702
Absolutely.. client/dns/firewall/squid is on zebedee... is just another machine on that network. Unfortunately though
HostnameLookups is already set to off... the default. I have hardly configured this machine so mostly everything will be at the default values apart from what I believe to be the obvious necessities to get it up. Maybe that is a clue as to my problem.
I was surprised to see the lack of reference to the machine making a call to the apache server and getting a response in the tcpdump... nothing.   odd.
thanks for your help..

Expert Comment

ID: 13506844
So what's the IP of zebedee.magic.sound-effects-library.com ?  I assumed it was because I saw http from zebedeee to

If it's not the apache config, then maybe the server doesn't have the right default gateway?

What is your firewall's internal IP address and what is the output of netstat -rn command on the apache server?

Author Comment

ID: 13507191
zebedee on the inside is outside and I think you maybe right ... netstat -rn gives

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface U         0 0          0 eth0   U         0 0          0 eth1         UG        0 0          0 eth0

In the mandtake control panel I can see that the gateway for (eth1) is  this I am sure should be but it doesnt seem happy to let me change it there..
I got a good feeling that your going to know a way  !

Expert Comment

ID: 13507444
unfortunately, I'm an old school unix guy so don't know as much about mandrake and how it is configured.  
If you want to go outside the GUI, from a prompt as root, you can run:

route add -net default gw dev eth0

this should change the route but (I believe) only until you reboot.  For permanent changes, you should be able to edit the file:


GATEWAY=    # or the IP address of your gateway device - your default gateway

BTW - Is that the netstat output from the mandrake box or from the firewall?  It looks like the firewall.

If you want, go ahead and post the netstat -rn on the mandrake box before your changes and we can double-check the settings.


Author Comment

ID: 13507820
That was from the Mandrake box... revised it is now..

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface U         0 0          0 eth0   U         0 0          0 eth1         UG        0 0          0 eth1

which I really thought would have it in the bag... but no.

I have rebooted too..(netstat was after reboot). I initially used eth0 to bring the updates thro at time of build, its unconnected now. I am thinking of flipping eth1 with eth0 - just a whim ~ perhaps not very logical.

Accepted Solution

jeopboy earned 800 total points
ID: 13508035
if eth0 is disconnected, that is the problem.  The kernel still thinks it has a connection to the subnet.

Can you completely remove the IP information and disable eth0 from the mandrake control panel?  That should do the trick.

Author Comment

ID: 13508127
Well I take my hat off to you.. that did indeed do the trick. Thankyou very much for all your help. Have a pint on me I am delighted this has been getting me for quite a while..
Thanx again..

Expert Comment

ID: 13508445
Glad to help and thanks for the virtual pint (and the EE p'ints) ;-)

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