Basic DHCP on Cisco Router

Configuring DHCP IOS DHCP server

Sequence of DHCP messages :

1. Client sends a broadcast DHCPDISCOVER message to the server
2. The DHCP server replies with a DHCPOFFER message containing the IP address, subnet mask , gateway and other parameters.
3. The client sends a broadcast DHCPREQUEST message to the server, requesting the offered address.
4. The DHCP server replies with a broadcast DHCPACK packet to the client.

DHCP server was designed to work within the same broadcast domain as the clients.
If DHCP server is behind another router , that router must become a DHCP Relay Agent. The DHCP relay will intercept the broadcast DHCP messages from the client and will forward them to the server as unicast messages. See at the end of this post a setup based on this scenario.

My network setup in GNS3 shown below 

SSH useful commands

I post below some useful SSH commands


Secure Copy File Transfer

SCP copies files between hosts on a network. It uses ssh for data transfer, and uses the same authentication and provides the same security as ssh. Some examples here

From a remote host to  local host

scp -P10022 192.168.2.10:/home/stelios/Desktop/Etherchannel.zip /home/stelios/Desktop/  
 Etherchannel.zip                                            100% 137KB 136.6KB/s  00:00   

More that one file from localhost to remote host

scp -P10022 test01.txt test02.txt 192.168.2.10:/home/stelios/Desktop/  
 test01.txt                                                 100%  0   0.0KB/s  00:00    
 test02.txt                                                 100%  0   0.0KB/s  00:00    

From the local host to a remote host

scp -P10022 /home/stelios/Desktop/Multicast.zip 192.168.2.10:/home/stelios/Desktop/  
 Multicast.zip                                               100%  75MB  1.5MB/s  00:49    

Secure Copy  directory from local to remote host

scp -P10022 -r /home/stelios/Desktop/scp_test 192.168.2.10:/home/stelios/Desktop/  
 WHowe_gns3_vbox.pdf                                       100% 1902KB  1.9MB/s  00:00