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So slow Internet connection after scheduled maintenance on upstream provider(ISP). It could be multiple reasons such as software issue, hardware failure, bad patch cable , dirty fiber and trunk issue. Those are very rare case. Lately I noticed more trouble with MTU mis-setting on backbone routers. When ISP expends their backbone trunk, they put TenGigE card instead of SONET in these days. No wonder why they do that b/c GigE or TenGigE card is much cheaper then SONET card.

Here is common mistake is that the forget to change default MTU size(1500) of the fresh card from the box. Most of ISP set MTU on their backbone as upto 9180 or at least bigger than 1524 bytes (due to VLAN tag for internal use). Again, this is very rare case, but it happens. See how to verify MTU size wrong in the ISP backbone.

 MTU_issue_ISP.png

 

Last Updated (Saturday, 18 February 2012 00:49)

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Here is the sample configuration to allow traceroute(Unix or Network devices) and tracert(MS Windows)

"TraceRoute" commands of Unix and Cisco devices send UDP packets, while "TraceRT" commands in MS Windows is sending ICMP packets.
In both cases the returning packets are only ICMP. For "TraceRT".


Cisco Router#
Cisco Router#conf t

Cisco Router(config)#access-list 111 permit icmp any any time-exceeded
Cisco Router(config)#access-list 111 permit icmp any any unreachable or port-unreachable 

If you want to accept ping (ICMP echo-reply), it would be like below

Cisco Router#
Cisco Router#conf t
Cisco Router(config)#access-list 111 permit icmp any any echo-reply ; (ICMP type 0)
Cisco Router(config)#access-list 111 permit icmp any any time-exceeded
Cisco Router(config)#access-list 111 permit icmp any any unreachable or port-unreachable ; (ICMP type 3)


Then, apply WAN Serial interface(in this example)


Cisco Router#
Cisco Router#conf t

Cisco Router(config)#interface serial1/1
Cisco Router(config-if)#ip access-group 111 in

* If you have outbound ACL, you need to allow UDP and ICMP echo. If you have inbound policy, then you don't need below.

Cisco Router(config)#access-list 111 permit UDP any any gt 3000
Cisco Router(config)#access-list 111 permit icmp any any echo ; Echo request (type 8)
 

 ** If you see below output, it is evidence of missing "time-exceeded (ICMP type 11)"

Cisco Router#tr 200.200.200.1

Type escape sequence to abort.
Tracing the route to 200.200.200.1

  1 100.100.100.2 24 msec 24 msec 8 msec
  2  *  *  *
  3  *  *  *
  4  *  *  *
  5  *  *  *
  6 200.200.200.1 44 msec 52 msec *
Cisco Router#

 

 

Last Updated (Tuesday, 30 November 2010 20:24)

 

Here is quick guide of "How to restore Firefox default setting"

1. From bottom status bar, click Start > Run and put " firefox.exe -safe-mode "

 restore firefox default setting picture 1

 

Last Updated (Thursday, 15 September 2011 13:52)

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Here is useful tips to reduce Firefox high memory usage. Before changing options, you are better to save previous option in case any issues.

Here is the Firefox 3.6 memory usage before changes by Taskmgr. As you can see Firefox is taking 252M. Let's see how much we can reduce Firefix high memory usage after modification.

 How to reduce Firefox high memory usage picture 1

 

Last Updated (Thursday, 15 September 2011 13:52)

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Here is quick steps of ' How to upgrade Free ESXi 3.5 to ESXi 4.0 '. The procedure is pretty straightforward, but it take a time... be patient!.  Of course, before start this process, make sure you bot copy of VMs.

1. Backup

It is very important step. Everything is on you risk, but Always Always Always backup is needed in any circumstance. Don't make a situation to pull your hair in your failure. Definitely not a good thing.

We have installed Veeam FastSCP free version. Yes it does support Free ESXi 3.5 and 4.0. It is really fast compared to other ways to back up and restore.

Also, before starting upgrade your Free ESXi3.5, power down all the guest OSs and put your ESXi 3.5 on "maintenance mode"

 

 2. Download upgrade package

You need to download ESXi 4.0 upgrade package from the VMware website. The file looks like "ESXi-4.0.0-xxxxxx-upgrade-release.zip". You need to register, not just only get the package, but also getting ESXi 4.0 licenses.  


 3. Download Free vSphere Client 4.0 

You can download vSphere Client 4.0 from VMware website, or you can extract it from the ESXi 4.0 package using 7-zip manager. See the path to extract below picture.

ESXi-4.0.0-1.9.208167-upgrade-release.zip\VMware-viclient.vib\data.tar.gz\data.tar\.\4.0.0\client\

Picture 3 of How to upgrade ESXi 3.5 to 4.0

 

Last Updated (Tuesday, 14 December 2010 17:39)

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I always curious about universe, but I couldn't afford buying decent telescope. This is cool website and you can learn something you never think about it. 

What is a WorldWid Telescope?

The WorldWide Telescope (WWT) is aenvironment that enables your computer to function as a virtual telescope—bringing together imagery from the best ground and space-based telescopes in the world for a seamless exploration of the universe.

 

Last Updated (Sunday, 20 May 2012 11:54)

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