Cannot ping to my machine from another subnet

Basel · 04-23-2010, 10:08 AM

I installed apache2 on my Ubuntu machine and I am trying to access the server from another subnet. The server is connected using ethernet and has a static ip address. I can ping from the server to any machine in the other subnet but non of the machine on that subnet can ping the server.

iptables does not seem to be running

Code:

# service iptables status
iptables: unrecognized service

and its rules are

Code:

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

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

also ufw seems to be inactive

Code:

# ufw status verbose
Status: inactive

The output of netstat shows that apache is listening on port 80

Code:

# netstat -plantu | grep apache
tcp6       0      0 :::80                   :::*                    LISTEN      1113/apache2

What is preventing my machine from being accessed from the other subnet?

TB0ne · 04-23-2010, 10:14 AM

You don't have the right network information set up. Either your default gateway is wrong/missing, or some other piece (subnet mask, etc.).

If you can't get off your one subnet, chances are it's the default gateway.

anomie · 04-23-2010, 02:14 PM

Right, if you still can't figure it out we'd need to see some IP info:

Code:

# ifconfig

Code:

# netstat -rn

Given that you can actually ping from the borked host to external hosts means it would also be worthwhile to check:

Code:

# sysctl net.ipv4.icmp_echo_ignore_all

Basel · 04-24-2010, 01:46 PM

I am sorry guys for taking this long to get back to you, I got busy yesterday.

Here is the output:

Code:

~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx  
          inet addr:128.10.160.xxx  Bcast:128.10.160.255  Mask:255.255.255.0
          inet6 addr: xxxx::xxx:xxxx:xxxx:xxxx/xx Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:31 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3732 (3.7 KB)  TX bytes:6846 (6.8 KB)
          Interrupt:29 Base address:0xc000

Code:

~$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
128.10.160.0    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         128.10.160.251  0.0.0.0         UG        0 0          0 eth0

Code:

~$ sysctl net.ipv4.icmp_echo_ignore_all
net.ipv4.icmp_echo_ignore_all = 0

TB0ne · 04-24-2010, 04:01 PM

Quote:

Originally Posted by Basel

I am sorry guys for taking this long to get back to you, I got busy yesterday.

Here is the output:

Code:

~$ ifconfig 
eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx  
          inet addr:128.10.160.xxx  Bcast:128.10.160.255  Mask:255.255.255.0
          inet6 addr: xxxx::xxx:xxxx:xxxx:xxxx/xx Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:31 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3732 (3.7 KB)  TX bytes:6846 (6.8 KB)
          Interrupt:29 Base address:0xc000

Code:

~$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
128.10.160.0    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         128.10.160.251  0.0.0.0         UG        0 0          0 eth0

Code:

~$ sysctl net.ipv4.icmp_echo_ignore_all
net.ipv4.icmp_echo_ignore_all = 0

Ok. Is all that right?? We don't know the particulars of your network, or the information you got from your network guys. The .251 for the default gateway looks suspicious to me, but I (as a rule), always set default gateways to .1, but again, that's all up to your network guys.

Best thing to do would be to confirm with them the default gateway, and subnet mask.

anomie · 04-26-2010, 02:26 PM

128.10.160.251 is definitely an unusual default router address. (i.e. Better double check, as mentioned.)