Networking

In Corporate environments with number of servers, system to system communication plays a key role in managing your environment. As the number of systems grows in the network maintaining proper track of network devices and communication between the devices provides internal communication to the services running on different servers, remote access management and file transfers etc..

1. Network Basics.

2. Routing Explanation.

3. Linux Networking.

  . Ethernet device Configuration

  . Bonding/Bridging

  . Vlans

 

1. Network Basics

  If you look at the network devices at home, which are accessing your wireless router. Each device accessing your WiFi router is assigned with an IP Address, by which the wireless router communicates with the devices and send/receive  packets with the requests made.

So in this case, in order to have internet access( ex: google, yahoo access ) , all the devices have to go through your wireless router. Which is nothing but a “Gateway”, for your home network. Technically the IP Address of your router is the Gateway IP address, that all your devices in your home network have to be in communication with to have internet access.

from windows host in your home network.

From the above output  Default Gateway “192.168.0.1”   is the ip address of your wireless  router.

  In order to have two devices to communicate on network, the corresponding network devices(network adapters/cards) have to configured with an IP Address. Which might be a static or dynamic address. By which the devices know where to go, and whom to talk with the request you made.

For any immediate connections in the same LAN( belonging  to same network), there is nothing involved with routing.

As long as the IP’s are in the same subnet/network. You can have all the connections go through a network switch, without specifying default gateway . All you need is the ip address and subnet mask.

server	IP Address	subnet mask
Alpha	10.20.30.100	255.255.255.0
Beta	10.20.30.200	255.255.255.0

With the Subnet mask 255.255.255.0 (Class C). From the IP Address of the server “Alpha”, the first three Octets belong to the subnet or network address i.e.. 10.20.30.0 ( Don’t get confused with subnet and subnet mask).

10.20.30.0 ---> Network address/Subnet, and with Class C subnet mask we have ip’s available from 1-255
0.0.0.0.100 --> host address
All together 
10.20.30.100 --> IP Address

And the host address of Alpha is 100, which is the last octet in “10.20.30.100”. The same follows for  server Beta as well.

Communication between two devices. Here we take the example of two servers communicating with a direct cable across them, with Ip addresses above and no switch or router in between them.  The corresponding Ip addresses are configured to the Ethernet adapters/Network Adapters(network cards), respectively for both Alpha and Beta.

With this configuration, Alpha and Beta will have Successful communication.

And in the case of multiple servers in the same network, we can  add a switch,  and still without a router ( or Gateway entry required) we can communicate among all the servers within the same network.

Here we  have three different servers, still  we can communicate among these without any router/routing required. All the data frames are are communicated on the broadcast domain 10.20.30.255. Any connected computer in the same set of switches is the set of same broadcast domain. All the packets broadcasted on the domain, are received by all the servers on the same network. Whichever request is going to the corresponding mac address/ip address is accepted by that and the rest are dropped.

So if you send a request from Alpha to Server Gamma, those packets will be reached to  the nic cards of both Beta and Gamma servers, the packet reached to Beta is dropped when it see the header information of the packet and determines, it is not destined for Beta. Gamma receives the packet and then responds to the request.

Ping response with the above connections and configurations:

 

For the configuration above there is no Gateway defined for the ethernet adapter. And there is successful communication between the two nodes through the switch.

2.Routing Explanation

Route is the address where you tell ur network configuration to reach out. Configuration without a route defined cannot reach out of the network your node is residing in.