How to add delete static routes in Windows XP

To add Static route in windows XP the  command is:

route add "network-address" mask "mask-of-network" "gateway

eg.

route add 10.0.0.0 mask 255.0.0.0 192.193.192.1


To delete Static route in windows XP the  command is:

route delete 10.0.0.0 mask 255.0.0.0 192.193.192.1

Difference between Frame, Packet Segment and Datagrams ?

These terms are used to refer at which OSI layer we are referring to, the data remain same but the headers and trailers are getting added or removed.

In Phy layer i.e. physical layer the actual data is in "bits" i.e. 0 and 1.

When it reaches to data link layer or Layer 2 it becomes "frame" with source and destination mac address getting added.

When it reaches the third layer or the networking layer it becomes a "packet" with source and destination IP address attached to it.

Finally it become "segment" at Layer 4 or TCP/IP layer. Basically "segment" term is used for TCP connections and "datagrams" for UDP.

So what about other layers like : session, presentation and application ? In these layers the data is termed as "PDU" or "protocol data unit".

So when someone says, that a "frame" is being received by a networking device, then you know that the device is switch.

Router receives a packet and process it.

Windows and Linux Tool to compare and merge files

Windows :

1) Winmerge : http://winmerge.org/
     Freeware.

2) Araxis : 30 days trial period

http://www.araxis.com/merge/

Linux :

1) Meld:  freeware
     http://meldmerge.org/ 

2) Guiffy : http://www.guiffy.com/
    21 days trial period.

3) Kdiff3 : http://sourceforge.net/projects/kdiff3/
     freeware and good to use.

DHCP option 82 how to enable in Windows and LINUX DHCP Server and DHCP Relay?

In Windows 2003 server "DHCP option 82" is not enabled by default. We need to follow below method to enable it.

http://blogs.technet.com/b/teamdhcp/archive/2009/07/06/dhcp-server-callout-api-usage.aspx

In ISC-DHCP server we can add options tag in dhcpd.conf file to enable this option.

In ISC-DHCP Relay we use this command to enable this option :

dhcrelay -d -a server_ip

"-a" option add "Circuit id" to the packets passing through relay. In this "Remote id" is not enabled by default, we need to modify the code to use it. Also "link state" sub -option is not supported as of now , we need to modify the code to use it, not sure why in Release notes they say that it is supported. I did not see any proper code to support it. Also it doesn't have config file to add this option.

If you know how to do it please let me know.

How to know the status of DHCP Server if it is down ?

Through  ISC-DHCP forum i came to know about two great tools which will check the status of DHCP Server and if it is down will inform admin or take appropriate action.

http://www.mavetju.org/unix/general.php

http://www.phpclasses.org/package/6621-PHP-Send-queries-to-a-DHCP-server.html

I have not used it myself, you can try them and let me know your comments.