Connect to Network (can ping router) but can't access the Internet

DGrieve · 03-08-2008, 01:28 PM

As the subject says, I'm connected to the network (I can ping the router, SSH to other computers, and it can be SSH'd to) so it's there. But I'm unable to access the Internet via that machine. So far I've just tried accessing websites via links, and trying to open FTP connections and it's always the same sort of error "Network cannot be reached" etc.

I'm trying to give the computer a static network assigned IP (192.168.1.2 in this case) so that my router's port forwarding works. If I set the computer back to dhcp it works fine (but assigns 192.168.1.3) which isn't desirable.

If anyone could shed some light it would be most appreciated, I can post any info that's required.

I'm running CentOs 4.4.

Hewson · 03-08-2008, 02:02 PM

Code:

netstat -rn

what does netstat say? My 1st guess is that you don't have a default route set.

If you dont have that set you wont be able to get out of your network, in this case:

Code:

route add -net 0.0.0.0/0 gw <ip of gateway to the outside world>

Also it is a good choice to use static IPs if you are planning to use port forwarding. Just make sure your DHCP server does not have the IP you use as your static address in its dhcp server pool. If it does you could end up with 2 machines with the same IP address and that leads to all kinds of weird network problems.

anomie · 03-08-2008, 02:03 PM

Let's see the results of:

# ifconfig

# netstat -rn

# cat /etc/resolv.conf

From your post it sounds like you forgot to add a default route, but might as well check other common issues as well.

DGrieve · 03-08-2008, 02:12 PM

OK here we go, I think you may be right about the route (doesn't look right).

ifconfig

Code:

eth0      Link encap:Ethernet  HWaddr *************
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::206:4fff:fe06:d9d6/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:499 errors:0 dropped:0 overruns:0 frame:0
          TX packets:252 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:101127 (98.7 KiB)  TX bytes:34507 (33.6 KiB)
          Interrupt:193 Base address:0xa000

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:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:560 (560.0 b)  TX bytes:560 (560.0 b)

netstat -rn

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.1.0     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

cat /etc/resolv.conf

Code:

; generated by /sbin/dhclient-script
search home
nameserver 192.168.1.1

Hewson · 03-08-2008, 02:21 PM

ya just add this line and you should be GTG (assuming your /etc/resolv.conf is all good)

Code:

route add -net 0.0.0.0/0 gw 192.168.1.1

DGrieve · 03-08-2008, 02:24 PM

Fantastic

That worked brilliantly.

Just another question, I restarted the computer and it didn't work again, as the route I'd added wasn't there anymore. Is there a file I can edit to append the line so that it is there all the time? Or should that not be happening.

Hewson · 03-08-2008, 02:34 PM

a quick and dirty way would be to add the route command to /etc/rc.local it will then be run @ start up.

I believe w/ cent you can make a route file (so that the routes are restored with each network restart) in /etc/sysconfig/network-scripts for your eth0 interface. I can't connect to my cent box from where I am right now so i cant give you much information on syntax or the name of the file. if you chose to go this route (no pun intended) do a quick google search for redhat static route

DGrieve · 03-08-2008, 02:44 PM

Thanks for the nudge in the right direction Hewson, I decided to take the network-scripts route (I stole your pun!) instead of using the /etc/rc.local method.

I had to create a file called 'route-eth0' in /etc/sysconfig/network-scripts, and just put this line in:

Code:

0.0.0.0/0 via 192.168.1.1

Seems to have worked fine after restarting the network service, will give a full computer reboot a shot now. Thanks again.

anomie · 03-08-2008, 04:41 PM

IIRC, another way to preserve default gateway (to survive a reboot) is by adding

GATEWAY=a.b.c.d

to /etc/sysconfig/network.

tarsnapcific11 · 04-02-2014, 07:47 AM

Same problem i facing and it get resolve after add in rout
Thankq very much