2005-01-04T09:46:12Z

Mbonani: /* IP Address Range & Associated S-bots */

IRDIA assigned some fixed IP to be used by the s-bots in the lab. This howto provides all the information required to access the s-bots and to modify the associations IP/s-bot.

==IP Address Range & Associated S-bots==

Here below, there is the list of IP addresses allocated to the s-bots. The first column shows the IP address, the second the name stored in the DNS, the third is the actual number of the s-bot binded to the address.

{| border="1" cellpadding="5" cellspacing="0" align="center"
!IP
!DNS Name
!S-bot #
|-
|164.15.10.150
|sbot1
|19
|-
|164.15.10.151
|sbot2
|15
|-
|164.15.10.152
|sbot3
|8
|-
|164.15.10.153
|sbot4
|12
|-
|164.15.10.154
|sbot5
|21
|-
|164.15.10.155
|sbot6
|13
|-
|164.15.10.156
|sbot7
|23
|-
|164.15.10.157
|sbot8
|24
|-
|164.15.10.158
|sbot9
|25
|-
|164.15.10.159
|sbot10
|26
|-
|164.15.10.160
|sbot11
|27
|-
|164.15.10.161
|sbot12
|28
|-
|164.15.10.162
|sbot13
|
|-
|164.15.10.163
|sbot14
|
|-
|164.15.10.164
|sbot15
|
|}

For instance, if you need to login into s-bot number 15, you can type either <tt>ssh root@164.15.10.151</tt> or <tt>ssh root@sbot2.ulb.ac.be</tt>.

==How to Avoid to Remember all the IPs of the S-bots and to Login into the Right One==

If you use computer names with SSH, usually your computer converts the name into an IP address ''first'' by checking into <tt>/etc/hosts</tt> and then by querying the DNS.

Therefore, in order to avoid to look at this page each time you want to know which is the IP address of s-bot X, you can modify your <tt>/etc/hosts</tt> and insert something like:

164.15.10.150 sbot19
164.15.10.151 sbot15
164.15.10.152 sbot8
164.15.10.153 sbot12
164.15.10.154 sbot21

After this modification, <tt>ssh root@sbot8</tt> will immediately connect to 164.15.10.152.

==How are IP Addresses Assigned and How to Change them==

When switched on, the s-bots connect to the wireless LAN. The wireless base-station is <tt>nobel.ulb.ac.be</tt> and works as a bridge between the wireless and the fixed networks. This means that the base-station receives all the packets for the s-bots from the fixed network and routes them into the wireless one, and the other way round too. No manipulation of the packets occurs.

After the sbots connected to the wireless lan, they broadcast a DHCP request for an IP address. Being this a normal packet, the base-station routes it to the fixed network. The DHCP server on <tt>iridia.ulb.ac.be</tt> receives the request and answers to it.

The DHCP server assignes IP addresses checking the MAC address stored in the request.
The server configuration file is <tt>/etc/dhcpd.conf</tt> on <tt>iridia.ulb.ac.be</tt>. An entry in this file looks like:

host <HOSTNAME> {
hardware ethernet <MAC ADDRESS>;
fixed-address <IP ADDRESS>;
}

The DHCP server must be restarted after having changed this file. To restart, type <tt>/etc/init.d/dhcp restart</tt>. Then check in <tt>/var/log/daemon</tt> to see if there are errors occured while the DHCP server was reading the configuation file.

----
--[[User:Hlabella|haiax]] 15:11, 16 Dec 2004 (CET)