[vMotion] The reason of sending RARP packet after vMotion finished

Recently I read the article about How vMotion impacts the forwarding table, I found I didn't quite get understood the following sentence:
"The following article mentioned "When the VM-MAC1 is moved from Host 1 to Host 2 through vMotion process a Reverse ARP (RARP) is issued by Host2’s kernel module on behalf of the VM-MAC1."

After searching RARP and vMotion information, I know why RARP is used here. The answer is quoted from here:
"The goal for sending these frames is to make sure the physical switches in the network learns the location of the Virtual Machines. A physical switch does this learning by observing each incoming frame and make a note of the field called Source MAC Address. Based on that information the switches build tables with mappings between MAC addresses and the switch port where this address could be found."

So, in sum, physical switches and vSphere will update their forwarding table by receiving the broadcast address of RARP packet.

[ONIE] The related URL of Open Network Installation Environment

http://onie.github.io/onie/docs/index.html
https://github.com/onie/onie
http://onie.github.io/onie/

[VMware] NSX Topologies with Traffic Flows

http://packetpushers.net/wp-content/uploads/2013/09/PPP-VMware-NSX-Topologies-Traffic-Flows.pdf

[U-Boot] Use U-Boot command to reload image file and reboot

The following step is about the U-Boot to reboot your machine:

U-Boot>printenv

• You can find the image address and bootm address.

U-Boot>setenv ipaddr 192.168.4.40
U-Boot>setenv serverip 192.168.4.26
U-Boot>setenv ethaddr 00:01:02:03:04:05
U-Boot>setenv netmask 255.255.255.0
U-Boot>saveenv
U-Boot>tftpboot 0xA800000040000000 <<your image file>>
U-Boot>bootm 0xA800000040000074

[BPDU] To understand BPDU Filtering an BPDU Guard

Quote from http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_55_se/configuration/guide/swstpopt.html#wp1046220

Understanding BPDU Guard

The BPDU guard feature can be globally enabled on the switch or can be enabled per port, but the feature operates with some differences.

At the global level, you enable BPDU guard on Port Fast-enabled ports by using the spanning-tree portfast bpduguard default global configuration command. Spanning tree shuts down ports that are in a Port Fast-operational state if any BPDU is received on them. In a valid configuration, Port Fast-enabled ports do not receive BPDUs. Receiving a BPDU on a Port Fast-enabled port means an invalid configuration, such as the connection of an unauthorized device, and the BPDU guard feature puts the port in the error-disabled state. When this happens, the switch shuts down the entire port on which the violation occurred.

To prevent the port from shutting down, you can use the errdisable detect cause bpduguard shutdown vlan global configuration command to shut down just the offending VLAN on the port where the violation occurred.

At the interface level, you enable BPDU guard on any port by using the spanning-tree bpduguard enable interface configuration command without also enabling the Port Fast feature. When the port receives a BPDU, it is put in the error-disabled state.

The BPDU guard feature provides a secure response to invalid configurations because you must manually put the interface back in service. Use the BPDU guard feature in a service-provider network to prevent an access port from participating in the spanning tree.

Understanding BPDU Filtering

The BPDU filtering feature can be globally enabled on the switch or can be enabled per interface, but the feature operates with some differences.

At the global level, you can enable BPDU filtering on Port Fast-enabled interfaces by using the spanning-tree portfast bpdufilter default global configuration command. This command prevents interfaces that are in a Port Fast-operational state from sending or receiving BPDUs. The interfaces still send a few BPDUs at link-up before the switch begins to filter outbound BPDUs. You should globally enable BPDU filtering on a switch so that hosts connected to these interfaces do not receive BPDUs. If a BPDU is received on a Port Fast-enabled interface, the interface loses its Port Fast-operational status, and BPDU filtering is disabled.

At the interface level, you can enable BPDU filtering on any interface by using the spanning-tree bpdufilter enable interface configuration command without also enabling the Port Fast feature. This command prevents the interface from sending or receiving BPDUs.

[Google Chart] Some examples of using Google Chart API in Python

Here are some example codes of using Google Chart APIs written in Python that I wrote several years ago. And some output image for reference.

• To generate multi-line chart:

def createMultiLineChart(rows, max_value):
urls = "http://chart.apis.google.com/chart?" + \
"chs=" + str(300+24*rows.__len__()) + "x200" + \
"&chd=t:" + ",".join([str(i[1]) for i in rows]) + "|" + ",".join([str(i[2]) for i in rows]) + \
"&cht=lc" + \
"&chls=2,1,0|2,1,0" + \
"&chco=0000ff,ff0000" + \
"&chtt=SMT%20Scrap%20Rate" + \
"&chxt=x,y" + \
"&chg=20,20" + \
"&chds=0," + str(max_value * 1.4) + \
"&chxl=0:|" + "|".join([str(i[0]) for i in rows]) + "|1:|" + "|".join(
[str(i * max_value * 1.4 / 10.0) + '%' for i in range(0,11)]) + \
"&chdl=Day%20S/R(%)|Night%20S/R(%)" + \
"&chm=s,0000ff,0,-1,8|s,ff0000,1,-1,8|N*f3*%,0000ff,0,-1,10|N*f3*%,ff0000,1,-1,10"
return urls

• To generate multi-line chart:

def createLineChart(rows, max_value):
urls = "http://chart.apis.google.com/chart?" + \
"chs=" + str(300+24*rows.__len__()) + "x200" + \
"&chd=t:" + ",".join([str(i[1]) for i in rows]) + \
"&cht=lc" + \
"&chls=2,1,0" + \
"&chco=8080ff" + \
"&chtt=SMT%20Scrap%20Rate" + \
"&chxt=x,y" + \
"&chg=20,20" + \
"&chds=0," + str(max_value * 1.4) + \
"&chxl=0:|" + "|".join([str(i[0]) for i in rows]) + "|1:|" + "|".join(
[str(i * max_value * 1.4 / 10.0) + '%' for i in range(0,11)]) +\
"&chdl=S/R(%)" + \
"&chm=s,80C65A,0,-1,10|N*f3*%,8080ff,0,-1,10"
return urls
P.S: It is almost the same as multi-line chart so that I don't provide the image.

• To generate bar chart:

def createBarChart(rows, max_value):
urls = "http://chart.apis.google.com/chart?" + \
"chs=" + str(300+24*rows.__len__()) + "x200" + \
"&chd=t:" + ",".join([str(i[1]) for i in rows]) + \
"&cht=bvg" + \
"&chco=1d89f9,c6d9fd" + \
"&chtt=SMT%20Scrap%20Rate" + \
"&chxt=x,y" + \
"&chg=20,20" + \
"&chds=0," + str(max_value * 1.4) + \
"&chxl=0:|" + "|".join([str(i[0]) for i in rows]) + "|1:|" + "|".join(
[str(i * max_value * 1.4 / 10.0) + '%' for i in range(0,11)]) +\
"&chdl=S/R(%)" + \
"&chbh=14,9,15"
#"&chf=bg,s,ffffef"
return urls

• To generate pie chart:

def createPieChart(rows, legend):
urls = "|".join([i[0] for i in rows])
urls = urls.replace(' ','_')
urls=urls.encode('utf8')
urls=urllib.quote(urls,'&=')
return "http://chart.apis.google.com/chart?" + \
"chs=600x150" + \
"&chd=t:" + ",".join([str(i[1]) for i in rows]) + \
"&cht=p3" + \
"&chtt=" + legend + \
"&chl=" + urls

[Linux Command] Redirect stderr to stdout and output to terminal and log into file at the same time

If you want to redirect stderr to stdout, append this at your command: 2>&1 , and also for outputting to terminal and logging into file you should use tee.
Both together would look like this:
$ yourcommand 2>&1 | tee yourlogfile.log