can't connect to router from server

[peterp53]

I have a server with Ubuntu 10.04LTS that I have been running for some time, no problems connecting to the net, updating Ubuntu etc.
I also have a billion router that I upgraded the firmware on it since then something has changed and I have not been able to ping the router from the server.
Using the domain address I can connect to the server externally so incoming works fine just can't connect out. Any help would greatly appreciated.

[Krendoshazin]

It sounds like the IP address of the router may have changed due to the firmware upgrade. If you're getting an IP address through DHCP, then it makes perfect sense that it would still work even with a different IP address on the router. Try running the command route as root and you should find the IP address there - it will be listed as the gateway address.

[peterp53]

This is the route information

Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
link-local * 255.255.0.0 U 1000 0 0 eth1
default 192.168.1.1 0.0.0.0 UG 100 0 0 eth1

does this look to you Krendoshazin I am not sure myself?

[Krendoshazin]

This is the route information

Destination     Gateway         Genmask         Flags Metric   Ref    Use Iface
192.168.1.0     *                 255.255.255.0       U     0        0        0 eth1
    link-local      *                 255.255.0.0          U     1000   0        0 eth1
default         192.168.1.1     0.0.0.0                 UG   100     0        0 eth1

It looks like your gateway IP is 192.168.1.1, the other 2 can be ignored. Try pinging that IP and see what you get.

[peterp53]

This is what I am getting

PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted


If "default 192.168.1.1 0.0.0.0 UG 100 0 0 eth1" is what it is using. Then is the netmask wrong because on the router it is 255.255.255.0

the other thing is the "DHCP Server" on the router is using 192.168.1.1 to 192.168.1.20 should the range be above the the gateway ip or doesn't matter?

[Krendoshazin]

Genmask is not the netmask as far as I'm aware. I can't give you an exact explanation as to what it is, but here is mine:

bash-4.0# route
Kernel IP routing table
Destination      Gateway         Genmask           Flags Metric Ref    Use  Iface
default           192.168.0.254  0.0.0.0             UG     0        0        0   eth2
192.168.0.0     *                   255.255.255.0   U       0        0        0   eth2

and this is my main system:

bash-4.0# ifconfig
eth2      Link encap:Ethernet  HWaddr 00:05:5D:DD:94:4E
            inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0

As you can see the genmask on the router is different to the netmask defined on the computer.

Are you sure that the DHCP range starts at 192.168.1.1? If the router is using that address, then I would expect it to start at 192.168.1.2. If this really is the DHCP range, then I would move the router outside of that range to avoid conflicts.

Also for your problems with ping, try running it as root and see if that works. I think that's likely a permission problem on the computer itself.

[peterp53]

Hi Krendoshazin,
Yes I see what you mean about the genmask so that can be ruled out. I changed the range of the DHCP on the router it now starts a 192.168.1.2 . I then rebooted the router and server but still get "ping: sendmsg: Operation not permitted" I pinged using sudo so it was a root command.
Im using a book called "Ubuntu Linux Toolbox" it said to use the arp command if the gateway can't be reached I did this and the gateway did not show so I added the gateway ip and the router mac address I then pinged again still the same.
I then did and ip neighbor command and got

192.168.1.1 dev eth1 lladdr 00:04:ed:db:d3:e3 PERMANENT

so it shows up

I then did an arp command to see if I could arp my laptop on the network

sudo arping -I eth1 192.168.1.5
ARPING 192.168.1.5 from 192.168.1.4 eth1
Unicast reply from 192.168.1.5 [A0:88:B4:E2:10:BC] 1.574ms

as you can see, using a command from the server 192.168.1.4 I can arp the the laptop which is 192.168.1.5 so the gateway to the laptop must be working.

[peterp53]

Just thought I would let you know Krendoshazin that the probelm is fixed I finally found it. It was the gateway ip address that had changed as you suggested and it was in the /etc/network/interfaces file

Thanks for you help