Friday, April 28, 2006

MTU Size

To check the MTU size between your PC and server, do the following in DOS:

ping -f -l 1500

Pinging [] with 1500 bytes of data:

Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

It means the packet is to big for the MTU size, reduce the size of the packet until you find out what is the optimum size:

ping -f -l 1473

Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

ping -f -l 1472

Reply from bytes=32 time=6ms TTL=64
Reply from bytes=32 time=3ms TTL=64

as you can see the optimum packet size is 1472. Now set your MTU size on your network adapter to: 1472 + 28 (You add 28 bytes because 20 bytes are reserved for the IP header and 8 bytes must be allocated for the ICMP Echo Request header).

Yes, it is 1500 MTU size. That is because I am using ADSL with PPPoA, which by default has MTU size of 1500.

Note: for Linux, the command is:

[root@fedora postfix]# ping -s 1480 -c 100 -M do
PING ( 1480(1508) bytes of data.
ping: sendmsg: Message too long
ping: sendmsg: Message too long

--- ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1000ms

reduce the size of the packet to 1472

[root@fedora postfix]# ping -s 1472 -c 100 -M do
PING ( 1500(1528) bytes of data.
1508 bytes from ( icmp_seq=0 ttl=248 time=298 ms
1508 bytes from ( icmp_seq=1 ttl=248 time=390 ms
1508 bytes from ( icmp_seq=2 ttl=248 time=294 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 294.271/327.895/390.728/44.468 ms, pipe 2

Thursday, April 27, 2006

Exchange 12 ROCKS!!

I can't wait for this one coming out!! The new Microsoft Exchange Server -
code name Exchange 12 is massive and very flexible. Check the following

Automatic Client Configuration
Today, configuring the Outlook desktop or mobile clients prior to first use
is complicated, requiring users to enter confusing technical information.
Exchange 12 includes a new automatic discovery and configuration feature
that Outlook 12 and next generation mobile devices will use to configure
themselves completely, including all appropriate corporate policies. End
users will not be required to enter Exchange server names or other technical
information. This capability will spare the IT staff from having to create
complicated deployment or configuration scripts that help users set up
Outlook to connect to Exchange. Additionally, mailbox moves will not require
manual reconfiguration of clients, and if a disaster occurs, clients will
automatically connect to moved or failed-over mailboxes on different
Exchange servers with no manual editing of Outlook or device connection
settings required

Mailboxes Etcetera
Users already rely on their mailboxes as repositories for every work
message they've ever received and even for actual deliverables. As mailbox
sizes have grown to accommodate user needs, the costs associated with
backup, restore, and migration have skyrocketed. Users need larger mailboxes
to handle this workload, but IT is hesitant to supply more space because of
the time and cost associated with managing a large mailbox. As a native
64-bit application (compatible with x64 servers), Exchange 12 lets an
organization keep all of its users' mail and calendar data on the server
where it can be reliably secured, backed up, and made available on a range
of devices. The 64-bit performance allows Exchange to address more memory,
it increases cache sizes, and it helps reduce disk I/O operations. As a
result, Exchange 12 makes more efficient use of each spindle (physical disk
drive) in existing Storage Area Network (SAN) systems while also enabling
inexpensive high-capacity disk drives to be used.
To address the high cost of backup associated with most messaging systems,
Exchange 12 introduces continuous replication features that use log file
shipping to keep a "rolling backup" of a mailbox database either on a local
disk set or on a disk set attached to a second, clustered server. In the
event of a disaster, a replica can be brought online and attached to any
Exchange 12 server in the network. These capabilities will allow many
organizations to move from expensive nightly tape backup procedures to
less-frequent tape or archival backups.

One Inbox
Users aren't just worried about e-mail, of course; they have to deal with
e-mail, faxes, voicemail, and documents-all of which have to be checked
constantly. But most users don't have the level of access they need away
from the office. Exchange 12 will provide a new unified messaging (UM)
solution that will enable end users to receive e-mail messages, faxes, and
voicemails in one Inbox (see Figure 3). Because in some cases the telephone
may be available when other clients are not, UM will support PIM access over
the phone. Users will be able to access their Inbox from any touch-tone
phone using either touch-tone commands or speech recognition. And via
text-to-speech translation, users can listen to their main Inbox items
(including e-mail, calendar, tasks, and contacts) read back to them. Users
can also interact with messages (reply, forward, and so on) and call other
users when appropriate. Corporate directory access will also be supported.

Flexible Server Roles
The next release of Exchange is being designed as a distributed system of
five server roles (see Figure 1). These roles-Mailbox, Hub Transport, Edge
Transport, Client Access, and Unified Messaging-allow Exchange 12 systems to
be installed with exactly the components organizations need, aiding
performance and reducing the surface area for attacks. Server roles are
deployed within the corporate network, with Active DirectoryR access, and
can also be deployed on a single server if needed. The only exception to
this is Edge Transport, which is deployed in the perimeter network with no
Active Directory access.

Sunday, April 23, 2006

Internet Explorer Corrupted!!

I had a problem with IE6 installed on Windows XP SP2. It was complaining about Visual C++ error on iexplorer.exe and close the browser once you clicked OK.

I run this command to restore IE to its original state:

rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 %windir%\Inf\ie.inf

it needs a CD for Windows XP SP2 as well as Windows XP to get the original files.

It doesn't really fix the issue, then I downloaded Hijack This:

Run the scan and paste the log to:

and remove the Nasty item from the computer. Reboot and aha!! fixed!!

Wednesday, April 19, 2006

Netbios over TCP/IP

If you have issue with Netbios over TCP/IP (e.g. can not browse computers on the network) you need to check and make sure the "TCP/IP Netbios Helper" is started.

If it could not start, make sure you have "Enable Netbios over TCP/IP" selected on your TCP/IP advanced setting.

However, if that setting has been selected but the service could not be started, go to your device manager, view hidden devices and Enable Netbios over TCP/IP, and restart.

original link: microsoft

Friday, April 07, 2006

Windows Event Triggers email notification

Tired of watching your Windows server event log? try with this VB Script to send email notification once Windows writes event to its event log.

How to setup the event triggers to notify you by email
1. Modify the eventSystemError.vbs and eventApplicationError.vbs script to suit your need (e.g. Computer name and email address )
2. Put your scripts on any folder (e.g. c:\tools )
3. Create the eventtriggers with the following syntax:

This will create eventtriggers called System Error, monitor the system log for any error and run the event.vbs
eventtriggers /create /tr "System Error" /l system /t error /tk c:\tools\eventSystemError.vbs

This will create eventtriggers called Application Error, monitor the application log for any error and run the eventSystemError.vbs
eventtriggers /create /tr "Application Error" /l application /t error /tk c:\tools\eventApplicationError.vbs

4. Please refer to this website if you need more options (e.g. domain\username authentication):



Thursday, April 06, 2006

Dual Daemon Postfix log rotate

With dual daemons Posftix, you might want to separate the log file for each daemon.

Let's say the 1st daemon logs to /var/log/maillog and the 2nd daemon logs to /var/log/maillog2, and you want to rotate the log files. I encountered issue when tried to rotate the second log file because maybe the pid of the daemons.

Anyway, I created the second logrotate file /etc/logrotate.d/maillog2 with the following content:

rotate 7
/bin/kill -HUP `cat /var/run/ 2> /dev/null` 2> /dev/null true
/etc/init.d/postfix reload > /dev/null
/etc/init.d/postfix2 reload > /dev/null