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Archives for November 2013

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How to perform an Android “Cache Partition Wipe”

You are most likely having some issues with your android device. One of the first things I recommend that you do is perform an Android “Cache Partition Wipe”. Applications save things to cache and sometimes the Android OS can have a hard time when corrupt data is in the cache.

A cache partition wipe only erases temporary system data that might be messing things up (no important personal data will be lost).  This can especially be a problem if you’ve recently done a system update.  Here are the steps:

  1. If your tablet is on, power it off.
  2. Press and hold Power until the device powers on, then immediately press and hold Volume Down (while still pressing Power). You will see the word Start with an arrow drawn around it.
  3. Press Volume Down twice to designate Recovery mode.
  4. Press Power to restart into Recovery mode. You will see an image of an Android robot with a red exclamation mark.
  5. While holding down Power, press Volume Up.
  6. Use the volume keys to scroll to “wipe cache partition” and press Power to select it.
  7. When done, select “reboot system now” and press Power to execute.

While these steps should work on all Android Devices I can verify that it works flawlessly on a Nexus 7 16GB (2013) model.

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How to manually install google android 4.4 kitkat on Nexus 7 2013 Wifi

NOTe this requires you to have a NExus 7 20013 Wifo (flo) device that is at Android 4.3 (JSS15R). If you need to check download the Android App
Nexus Update Checker”.

I hope this helps any Android newbies get KitKat installed a bit early. Unfortunately there is so many posts with bad or missing info that I figured I should do it up right.

  1. First thing you need to do is make sure that your device is in developer mod. To do this go into “About device” in Settings and tap on the “Build number” entry seven times, which will unlock “Developer Options”.
  2. Now that Developer Options are enable you will need to turn on “USB Debugging. To do so go into settings – “Developer Options” – Toggle on “USB Debugging”
  3. You will need to download Android SDK.  It is a ZIP file. Extract them to C:\users\%username%\SDK. Make That folder should contain 2 folders and SDK Manager.exe
  4. Run SDK Manager. If it doesn’t run it most likely you don’t have JAVA installed. There should most likely be a USB driver update. Install/Update Package

Install the Android Driver

Plug in your Android Device. You will need to open up Device Manager. Go to: Control Panel -> System -> Device Manager

You will see something like this:

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Right click it and install driver. Point it to the folder: C:\Users\Jared\SDK\sdk\extras\google\usb_driver. The driver will install.

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Make sure ADB see’s the Nexus 7 as well. In the platform-tool directory run the command “adb devices”. Let this window open.

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Great almost Done!

Download KitKat

The Nexus 7 2013 OTA (Over the Air) update needs to be downloaded. This is the same file that google would “eventually” let us all download. Save it as KitKat.zip and put it in C:\Users\%username%\SDK\sdk\platform-tools folder

Turn off the Nexus and turn it on by holding down Power and Volume Down buttons at the same time.

Connect your device to your computer using your Micro USB cable.

Get into “Recovery Mode” by hitting the Volume Down button. Use Power button to confirm.

Your device will reboot and you should now be seeing an Android logo with a red exclamation mark.  Hit power and then quickly hit Volume Up button.

Select “Apply Update from ADB”

Because you left the command prompt open you have to now type: “adb sideload KitKat.zip” without the quotation marks.

Now if you you get the error: “Error: device not found” while installing KitKat it means you have to install one more driver.

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Go to: Control Panel -> System -> Device Manager

You will see something similar again:

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Right Click “Galaxy Nexus”  and select “update driver software…”

On the next screen click this button:

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On the Next screen say “Let me pick from a list…”

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On the next screen select “show all devices”

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Say Have disk and point Windows to: C:\Users\Jared\SDK\sdk\extras\google\usb_driver

Hit Enter.

A Windows will pop up asking what you want to install. Select “Android Bootloader Interface”.

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Go back to the command prompt and type: adb sideload KitKat.zip

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After updating there is already several updates. Check for updates and let them apply right away. Also make sure all your app get updated as well.

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How to change the default image of a Pictures Folder

The screenshots from this are from a computer running Windows 8.1 Some versions of Windows might or might not allow you to actually pick out the picture.

Here’s a screenshot of my Pictures folder:

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You will notice I have already changed LifeFrame to a picture that I have specified. There are actually 3 pictures inside of that folder. Because I have selected a picture to be the default picture it will only show one.

Look at the folder called “Northern Lights at Matlock”. It currently is showing 2 pictures from that folder that the Windows operating system has automatically selected.

We are going to make that folder change it’s icon so it only shows the picture we want it to show. To do that we will change some settings.

Right click the folder and select properties. We will see something like this open:

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We will need to click on the “Customize” tab.

Once there, you will need to check a few items. Make sure the folder is optimized for “Pictures”. Then you need to hit the “Choose File…” button to select the picture that you want as the default picture on the folder.

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An “open file” dialog box will open and you should select a file that is INSIDE that same folder that you right clicked. Select the image you want and hit “open”.

It will look like nothing has happened. Hit “APPLY” and then hit “OK”. Voila the folder will now look different.

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If you have these options but it doesn’t work you might have been fiddling around with folders. I tend to see people have changed the “Default Folder Type” a folder that is higher up the food change and changed it to “Documents” or something similar. The “Default Folder Type” is the section that reads “Optimize this folder for:”. If you accidently selected “Also apply this template to all subfolder” a little bit higher up the food chain I have seen some funny results if you try and change a folder back later.

If that doesn’t work you might also want restore the folder default by hitting “Restore Default”.

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Finding the correct MTU for your network

Finding the Correct MTU for your Internet Connection

You might have heard To find the correct MTU for your configuration you must run a simple DOS Ping test. You will simply send out ping requests and progressively lower your packet size until the packet no longer needs to be fragmented. Please reference the following steps:

The command for this ping test is: ping www.jaredheinrichs.com -f -l xxxx

  • You can use any well known, pingable domain like ping www.jaredheinrichsphotography.com -f -l xxxx
  • There is a single space between each command.
  • “-l” is a lower case letter L, not the number one
  • The last four numbers are the test packet size.

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Tracing packet flow between a 2 switches and a router

Today we are going to see how switches and a router interact with each other by tracing ARP and ICMP packet flow. Here’s the network we are going to be playing with today:

Tracing packet flow between a 2 switches and a router 01

We’re going to look at a couple of things here. The biggest thing to keep in the back of your mind is two things.

  1. Switches break up collision domains
  2. Routers break up broadcast domains

While you will see me cover #1 in this post you should really check out my previous post to see better examples: Tracing packet flow between a Hub and Switch

We will focus most of this post on #2. Very much like all my post so it makes seeing what device is talking on the network I’ve handed out custom MAC addresses on each device. The MAC address will look like 0010.1111.1111 for PC1(192.168.1.1) and 0010.2222.2222 for PC2 (192.168.1.2). Each computer set to use ROUTER’s closest port as their “Default Gateway”.

All Devices all get turned on all at the same time. Non of them will have any information in their MAC or Routing tables.

I ran an “Arp –a” to prove it doesn’t know a thing about PC4’s MAC address yet. PC1 will ping PC4. Because PC1 has no idea PC4’s MAC address PC1 will need to send out an ARP request to figure out how to get to router one since 192.168.2.4 is not on the same network.

Tracing packet flow between a 2 switches and a router 02

This is how the header will look (notice it doesn’t have a target MAC address yet!)

Ethernet Frame Header Example

Tracing packet flow between a 2 switches and a router 03

The Broadcast ARP request is sent to SWITCH1. SWITCH1 now has learned about PC1’s MAC address and put it in it’s MAC Address table.

Tracing packet flow between a 2 switches and a router 04

The ARP broadcast is sent out all ports except the port it came in on. That means PC2, PC3 and ROUTER. Notice how the router  breaks up the broadcast domain. PC4->PC6 do not get the request.

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Router1 one sends back a request. It put’s PC1’s address in the “Target MAC” address field. It also puts it’s own address in the SRC MAC address field. It also put’s PC1’s MAC address into it’s own MAC Address table.

Tracing packet flow between a 2 switches and a router 04

Because ROUTER’s MAC address is in the SRC MAC field SWITCH1 will now add that address to it’s own MAC Address table:

Tracing packet flow between a 2 switches and a router 05

PC1 now knows how to get to it’s default gateway so that the packet can be routed to the external network 192.168.2.0 /24 network. The Router’s MAC address is added to it’s own MAC address table. PC1 creates a ICMP packet (layer 3) and encapsulates it in an Ethernet frame. That frame has a SRC MAC address of PC1 and a Destination MAC address of ROUTER.

Tracing packet flow between a 2 switches and a router 06

The ping (ICMP) is sent to SWITCH1. Switch knows where 192.168.1.254 is so it directly sends the frame to ROUTER.

Tracing packet flow between a 2 switches and a router 07

When the packet gets to ROUTER, ROUTER realized that it it doesn’t know what the MAC address is of PC4. Because ICMP requests are unicast, the router drops the packet. ROUTER then creates a ARP broadcast to find out what MAC address PC4 has.

Tracing packet flow between a 2 switches and a router 08

Router sends the ARP broadcast out to onto the network to SWITCH2. SWITCH2 will add ROUTER’s mac address to it’s MAC address table.

Tracing packet flow between a 2 switches and a router 09

Switch sends the ARP Broadcast out every port but the port it came in on. PC5 and PC6 drop the request. PC4 says “It’s Me!”

Tracing packet flow between a 2 switches and a router 10

As you would expect PC4 replies back to ROUTER by sending the response back on the network. SWITCH2 will add PC4’s MAC address to it’s MAC address table.

Tracing packet flow between a 2 switches and a router 11

ROUTER get’s PC4’s response back. ROUTER adds PC4’s MAC address into it’s MAC address table.

Tracing packet flow between a 2 switches and a router 12

It’s at this point something kind of funky happens. When I first started out I didn’t quite get it. It’s at this exact moment something will change on PC1’s command prompt. You will see a “Request timed out” message. The reason for this is the computer waited to hear back the ping (ICMP) reply but never received one because ROUTER dropped the packet because it didn’t know PC4’s MAC address. This does NOT mean that there is something wrong with the hardware!

Tracing packet flow between a 2 switches and a router 14

PC1 at this point says.. I’ guess something happened to my first ICMP request. I guess I should send request 2 of 4. So it creates a new request.

Tracing packet flow between a 2 switches and a router 15

PC1 will send out the 2nd ICMP ping out to the network. SWITCH1 get’s the frame. SWITCH2 says “Hey I know where ROUTER is” and forwards it directly to ROUTER.

Tracing packet flow between a 2 switches and a router 16

ROUTER and decapsulates the frame. It see’s the packet is needing to be sent on to PC4. It encapsulates the packet in a brand new Ethernet frame. Because of the previous ARP request it now has PC4’s MAC address. **NOTE** – The source MAC address on the new Ethernet Frame is set to ROUTER’s MAC address (gig0/1). The internal SRC IP address in the packet remains the same. If ROUTER changed the SRC IP address to it own IP address, PC4 would never know how to send the packet back to PC1!

Tracing packet flow between a 2 switches and a router 17

ROUTER sends the packet out to the network to SWITCH2

Tracing packet flow between a 2 switches and a router 18

SWITCH receives the frame and looks at the header. Because it knows where PC4’s MAC address it can send the frame directly to PC4.

Tracing packet flow between a 2 switches and a router 19

PC4 receives the frame and sends it back to PC1. It changes the Frame header by setting the originating MAC to itself and the destination address to ROUTER1. The IP address in the reply packet will be for PC1 and the SRC address is PC4’s.

Tracing packet flow between a 2 switches and a router 20

SWITCH2 will send the frame directly to ROUTER because it has it’s MAC address in it’s MAC table.

Tracing packet flow between a 2 switches and a router 21

ROUTER decapsulates the frame and see’s the packet is being sent to the IP address of PC1. It sees that it has PC1’s MAC address. It encapsulates the packet again and makes the SRC address it’s own MAC address. It makes the destination address that of PC1. It sends the packet on its way to to SWITCH1.

Tracing packet flow between a 2 switches and a router 21

Again SWITCH1 knows where to send the frame so it sends it directly to PC1. It knows because it has PC1’s mac address in it’s MAC address table. PC1 receives the ping ICMP reply.

Tracing packet flow between a 2 switches and a router 22

It’s at this very instant that we have completed the loop. PC1 has sent the ICMP request and it was routed to PC4. PC4 responded and it’s response was routed back to PC1. The Command prompt on PC1 will change ever so slightly to inform you that

Tracing packet flow between a 2 switches and a router 23

All subsequent requests (3 to 4) will all get replies assuming that there is no issues with the networking equipment.

Tracing packet flow between a 2 switches and a router 24

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