Hi,

1) I have a set of computers in networking environment
2) LAN 1: 192.168.51.0/24
3) LAN 2: 192.168.100.0/24
4) DC1
-Domain Controller (Win 2003 server)
-Domain name is "boba.com"
-It is at LAN 1 (the ip is "192.168.51.10)
-functioning also as DHCP, DNS and WINS
5) DC2
-Replica Domain Controller (Win 2003 server)
-It is at LAN 1 (the IP is "192.168.51.11")
6) XP1
-It is a client machine
-It is at LAN 1 (It gets the IP address from the DHCP; right now is "192.168.51.50"
7) XP2
-It is another client machine
-It is at LAN 2 (It gets the IP address from the DHCP; right now is "192.168.100.50"
8) Centos5
-It is a linux Machine (using Centos 5)
- I want to put it at the LAN 1
- When I checked .....I go to System > Administration > Network ( I will be in "Network Configuration")
- The DEVICE tab
      + The "Primary Status" --> ACTIVE
      + The " Device " --> eth0
      + The "Nickname" --> eth0
      + The "Type" --> Ethernet
      + Note: at the top, I see "ACTIVATE", "DEACTIVATE", etc
- The DNS tab
      + Host name: Centos5.Boba.com
      + Primary DNS: 192.168.51.10
      + Secondary DNS: 192.168.51.11
      + Other tabs are Blank
-The Hosts tab
      + It is BLANK now
      + Now, I will do the followings:
      + Click "New"
      + The IP --> " 192.168.51.25 "
      + Hostname --> " Centos5 "
      
- The next things that I will do:
      + I go to the "DEVICE", and click "ACTIVATE"
      + File > Save
      + Restart the machine
      + Note: I login to Centos5, and then I ping DC1 ....it can ping the ip correctly; so it works
      + Go to DC1, and try to ping Centos5

9) The problems:

-From DC1:
      + I can NOT ping Centos5 (or Centos5.Boba.com)
      + But I can ping DC2, XP1, XP2 Successfully
- From Centos5:
      + I can ping SUCCESSFULLY to DC1, DC2, XP1, XP2

10)  I go again to Centos5
- I execute the "ifconfig"
- I see the information as the followings:
      + inet address: 192.168.51.30 ( I do not know "from where it is coming from"; i did not see it before at System > Administration > Network ... (Actually, i set it as "192.168.51.25" )
      + broadcast: 192.168.51.255 ....
      + mask: 255.255.255.0

11) My questions:
First: How to fix it? [So it will work when i ping Centos5 or Centos5.Boba.com (from any machine; either at LAN 1 or LAN 2)] (It seems that Centos5 is "not recognized" by other machines) (Or the Firewall at Centos5 is ON? If yes, How to go to Firewall and turn it off? Show me please)

Second: When I ping (from Centos5) to any machine; the answers or the replies do not STOP (after 4 rows); it keeps "pinging" ......How to stop it? (what command should I use?); very annoying

12) Thank you

tjie