Archive for the ‘network’ Category

I need to share my cdrom over the internet, so this is what I did.
I’m using windows7 for the drive (don’t worry, I’m sharing a Centos CD for a remote install).

The quick steps are:

1. Turn off windows firewall.
2. Share the drive
3. Forward ports 135-139, 445 from your router to the machine (tcp and udp).
4. Access the drive as //ip.address.whatever/cdrom

1. Turn off the firewall

Start -> Control Panel -> System and Security -> Windows Firewall.

Then on left, click: Turn Windows Firewall on or off.  And I turned it off for public and home, then click ok. (don’t forget to turn it back on later).

2. Share the drive.
I insert the CentOS 5.4 64 bit CD into the drive.

Hit Windows-E, then right click on the CDROM (D:)

Share with -> Advanced Sharing…

Click Advanced Sharing

Check “Share this folder”

Change Share name to cdrom (or whatever, you don’t need to change it).

click permissions.  Now check that only “Read” is “Allow” for “Everyone”.

Now the share is available is \\my.ip.address\cdrom

Also note that running this over Samba worked even easier, and I recommend doing that instead of sharing from a windows box.

If you are doing a remote CentOS install, you (most probably) should use the network install. That way the remote machine can use a local mirror to get all the RPM’s, rather than going back to your CD to get it. It was an interesting exercise to install CentOS on a machine in the UK, when I’m sitting here in Brisbane, Australia.

yum install wireshark

First check the arp packets, type tshark -q -z “io,stat,1,arp”, then wait 10 seconds and hit Ctrl-C. Wireshark replaces ethereal.

[root@au1 ~]# tshark -q -z "io,stat,1,arp"
'Running as user "root" and group "root". This could be dangerous.
Capturing on eth0
781 packets captured

===================================================================
IO Statistics
Interval: 1.000 secs
Column #0: arp
|   Column #0
Time            |frames|  bytes
000.000-001.000       1        60
001.000-002.000       2       120
002.000-003.000       2       120
003.000-004.000       1        60
004.000-005.000       0         0
005.000-006.000       2       120
===================================================================

Now run the same thing looking at everything else:

[root@au1 ~]# tshark -q -z "io,stat,1,not arp"
Running as user "root" and group "root". This could be dangerous.
Capturing on eth0
624 packets captured

===================================================================
IO Statistics
Interval: 1.000 secs
Column #0: not arp
|   Column #0
Time            |frames|  bytes
000.000-001.000     112     10080
001.000-002.000      97      8694
002.000-003.000     111      9960
003.000-004.000     131     11754
004.000-005.000     114     10188
005.000-006.000      50      4500
===================================================================

and you can see that this is not the case right now. Recently we had a faulty device on the network that was absolutely hammering the local network (I was getting 800k/sec of ARP, and 1.2M/s of total traffic).

The usual way to determine if this is the case is to check the bandwidth on your managed switch, or the stats from your firewall, if you are unlucky then you won’t have this information.  In our case the network was unusable and we had an un-managed switch. So the quick way to determine the problem machine is to unplug the machines one at a time until the problem goes away. (or unplug them all and add them back in slowly).  YMMV.