# All of the sudden I can't connect!

## moevot

Hey guys I got a strange problem. 

I have been using a wired Ethernet connection for my Gentoo install and I have had no problem with internet connectivity. No net-setup was even required when I first booted up the liveCD. I am at the stage of the install where I need to setup networking on the actual device by emerging netifrc and creating symlinks to net.lo and all of that stuff and now I can't get a good connection. If I ping I get

```
PING www-bytemark-v4v6.gentoo.org (89.16.167.134) 56(84) bytes of data.

64 bytes from www.gentoo.org (89.16.167.134): icmp_seq=1 ttl=45 time=155 ms

ping: sendmsg: Network is unreachable

ping: sendmsg: Network is unreachable

ping: sendmsg: Network is unreachable

ping: sendmsg: Network is unreachable

ping: sendmsg: Network is unreachable
```

It flips back and forth between the error and an actual packet being recieved every once in a while. What info do you guys need to help me? Never seen anything like this and have done the install 4 times in the past. Now I cant even emerge anything because of this.

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## NeddySeagoon

moevot,

We need to find a shorter path to test, so we can determine if its you, or your ISP, or the big bad internet.

It sounds like the big bad internet is in the clear.

Are you using wired or wireless?  

Can you reliably ping your router?

Your router is the gateway in the top line.

```
$ route -n

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

0.0.0.0         192.168.100.253 0.0.0.0         UG    2      0        0 eth0

127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo

127.0.0.0       127.0.0.1       255.0.0.0       UG    0      0        0 lo

192.168.100.0   0.0.0.0         255.255.255.0   U     0      0        0 eth0
```

If you have several  lines that start 0.0.0.0 you have a different problem.

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## moevot

I am using a wired connection

```
$ route -n 

Kernel IP routing table 

Destination        Gateway                Genmask           Flags Metric   Ref    Use   Iface 

0.0.0.0              192.168.0.1           0.0.0.0              UG    100       0       0     eth0 

127.0.0.0           0.0.0.0                  255.0.0.0          U      0           0       0     lo 

192.168.0.0       0.0.0.0                  255.255.255.0   U      0          0       0     eth0

```

If I run ifconfig -a then I can see that eth0 has inet 192.168.0.9 which I can ping succesfully with 0% packet loss. What is the differnce between 192.168.0.0 and  192.168.0.9 (I know nothing about networking). So where should I go from here guys?

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## moevot

 *Quote:*   

> Your router is the gateway in the top line. 

 

I just pinged the router which is 192.168.0.1 which works as well. What is the difference in all of these ip's?

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## NeddySeagoon

moevot,

Every system on a network has an address. It much like your residential address and used for the same purpose. 

192.168.0.9 is the address of your PC on the network. When you ping that you are talking to the network card in your PC.

192.168.0.0 is the address of a whole network. In your case that network has a netmask of 255.255.255.0. you need both bits.

The netmask splits the address into the network part and the host part. 

Given  192.168.0.0 and netmask 255.255.255.0 first 192.168.0. is the network address and the last bit, the .0 the hast address.

The netmask is always an uninterrupted sequence of binary '1' followed by an  uninterrupted sequence of binary '0'.

255 is 11111111. 

It follows that your network 192.168.0. can contain 256 hosts. There are two reserved addresses.

The network address cannot be allocated to a host. That's 192.168.0.0 and nether can the broadcast address.

The broadcast address is by convention the last address in the network, or 192.168.0.255. You can't allocate it to a host either.

Putting this together with your routing table, from the bottom, 

```
Destination        Gateway                Genmask           Flags Metric   Ref    Use   Iface

192.168.0.0       0.0.0.0                  255.255.255.0   U      0          0       0     eth0 
```

That says to reach the 192.168.0.0 network, no gateway is required, just send the packets out of the eth0 interfacce.

I'll skip over 

```
127.0.0.0           0.0.0.0                  255.0.0.0          U      0           0       0     lo 
```

```
Destination        Gateway                Genmask           Flags Metric   Ref    Use   Iface

0.0.0.0              192.168.0.1           0.0.0.0              UG    100       0       0     eth0 
```

says to send any packets that have not been routed to  192.168.0.1 (your router) because it knows what to do with them. 

Your PC does not.

Your router will have another routing table. that describes how to reach the 192.168.0.0 network and a default route that points to your ISP.

The whole internet is put together like this. 

If you have traceroute, you can find out where the problem is ... maybe.

```
sudo traceroute -T google.com
```

will trace the route that packets take from you to google.com.

The first 'hop' will be to  192.168.0.1, your router, the next 'hop' will be to your ISP.

If you find a big timing gap, that hop has a problem.

A response like  

```
5  * * *
```

means that that host is not providing any information.

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## moevot

btw I resolved this. Just turned it off, went about my day, and rebooted and have never had this problem again. !@$%# networking man, its magic

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