Modify License MAC of Linux-based appliances on VM

This post entails the procedure of modifying License MAC address of any Linux-based Cisco UC appliances in Lab environment.

Procedures Overview.

  1. Customize BIOS of VM to boot from Red Hat Enterprise LINUX 5.
  2. Enter rescue mode, and enable root remote ssh access to Linux OS
  3. Access with root privilege and change License MAC to desired value.

Pre-requisites: Bootable image or CD of Red Hat Enterprise LINUX 5.

Detailed Step-by-Step Tutorial:

  1. Enable BIOS access by modify *.vmx file of VMware virtual machine.
    [For VMware Workstation only: close VMware Workstation application or VM’s Tab, then add bios.bootDelay = “5000″ to *.vmx file, which will introduce 5 seconds delay for system boot to let you press “ESC” to select the boot location.]
    Use VMware vSphere client to access ESXi host, navigate to Summary tab, right click datastore1 and select Browse Datastore…, download *.vmx to local PC, edit it by adding below line;
    bios.forceSetupOnce = “TRUE”;
    then upload it again to let the change take effect.
    NOTE that this parameter only takes effect only for one single instance of “power on” because “bios.forceSetupOne” will return to FALSE after you enter BIOS every single time. You will need to manually change “Enter BIOS of VMware Virtual Machine” to “TRUE” again if you want to enter BIOS for the second time. But, you changes in BIOS remains there permanently. Continue reading ‘Modify License MAC of Linux-based appliances on VM’ »

Hardware–At a Glance

Types of Hard Drivers

SATA: Commodity SATA drivers

Cheapest in Capacity, but medium in IOPS ( I/O Operations Per Second). Reliability of commodity SATA is their biggest issue.

SAS: Enterprise SAS drivers

SAS drives are usually only used in servers. They’re more expensive because they have better error correction and can come in speeds of up to 15,000 RPM, 2x-3x that of most SATA drives (4500-7200 RPM). More pricy than SATA driver in Capacity. 2 times more expensive than SATA driver in IOPS.

SSD: Solid State Drivers

Far too expensive in capacity, but much more cheaper than SATA and SAS in IOPS.

Input / Output Operations Per Second (IOPS)


Virtual Device Contexts (VDC)

What is VDC and how it works

VMware aims at server & application virtualization, while VDC is a virtualization technology for Networking devices and it enables several Virtual Multilayer Switches Instances (also named VDC instance or logical device) in a single physical Cisco Nexus device. Each Virtual Multilayer Switch Instance has its own independent and isolated control plane (a set of processes running in their protected memory space) which are, in particular, Layer 2 & Layer 3 protocols and services. Likewise, data plane can also be virtualized by allocating specific physical ports on line cards to a certain VDC instance. NX-OS is based on Cisco MDS 9000 SAN-OS platform, it introduces VDCs to enable device level virtualization. At the heart of NX-OS is the kernel and infrastructure layer. At any one point time, only a single instance of kernel will exist and provide an interface between higher layer processes and hardware resource of physical switches. Besides, only one single instance of kernel simplifies hardware resource management. VRF aims at network virtualization on Forwarding Table level, while VDC improves that to Process level, and finally, it will reach Haredware (CPU & Memory) leve.

VDC Architecture

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Virtual Port Channel (vPC) Basics

vPC Technology has been introduced by Cisco Nexus OS as a key component of Cisco Data Center Networking architecture. The major benefits it brings are:

  • Loop avoidance logic allows 2 physical connections from 1 device to 2 Nexus Switches to operate in active/active mode and eliminate STP blocked port to fully utilize the uplink bandwidth.
  • Layer 2 Loop avoidance logics implemented directly in hardware while STP relies on control plane to do that, thus it provides faster convergence upon link or device failure.
  • more efficient load balance than STP.

Most components or concepts of vPC technology are entailed in below picture.

vPC Basics

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Basic Tips for CUCM Troubleshoot & Verification

This thread focuses on the basic troubleshooting of those simple problems arising from install & initial setup, system configuration, daily maintenance tasks etc.

Monitoring TFTP / SFTP / FTP / Signaling events

Whenever you upload phone firmware or upgrading package through SFTP / FTP / TFTP, to verify if the uploading is in progress, you can capture relevant packets under CUCM OS CLI. This method also benefits your monitoring of signaling event on specific ports (2000 for SCCP, 1720 for H323, 1719 for GK, 5060 for SIP etc)

admin: utils network capture src <source IP addr> dest <destination IP addr> port <port number>

admin: utils network capture host <ip/arp/all …> <host ip address> port <port num>  // capture all IP packets to & from the host ip address with source or destination port equals to port num.

CUCM CLI Packet Capture

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Networking in VMware World

Terminologies in VMware Networking:

VMware Networking

The key virtual networking components provided by Virtual Infrastructure are:

  • Virtual Ethernet Adapters, used by individual virtual machines.
    In most cases, a virtual machine uses only one of the three types of virtual adapters.
    • vmxnet: works only if VMware Tools is installed in the guest operating system. The vmxnet adapter is designed for high performance. In most cases, when you select the flexible network adapter, this is the adapter used after VMware Tools is installed in the guest operating system.
    • vlance:  a virtual device that provides strict emulation of the AMD Lance PCNet32 Ethernet adapter. It is compatible with most 32-bit guest operating systems. This adapter is used when you select the flexible network adapter but VMware Tools is not installed in the guest operating system.
    • e1000: a virtual device that provides strict emulation of the Intel E1000 Ethernet adapter. This is the virtual Ethernet adapter used in 64-bit virtual machines. It is also available in 32-bit virtual machines. Continue reading ‘Networking in VMware World’ »

Windows 常用网络命令



  • netstat –s;按照协议种类分别列出统计信息。
  • netstat –e; 概况的列出以太网的统计信息,包括收、发的总包数,单播包,组播包,错误包和丢弃包等。
  • netstat –r;显示路由信息,类似于route print命令。
  • netstat –a;显示所有的有效连接(已建立Established、监听Listening)信息的列表。
  • netstat –n;显示所有已建立(Established)的有效连接,并以数字格式显示地址和端口号。
  • netstat –o;显示相对应的进程ID,然后通过Resource Monitor找到对应的具体应用程序。


  • ipconfig /release; 归还IP地址,
  • ipconfig /renew; 重新联系DHCP服务器,获取IP地址。


  • arp –a / –g; 查看本地ARP表中的所有项目。
  • arp –d; 清除本地ARP缓存条目。
  • arp –a <ip add>; 查看某IP对应的MAC地址。
  • arp –s <ip add> <MAC add>; 手动添加静态的ARP条目。
  • arp –d <ip add> <MAC add>; 手动删除静态的ARP条目。 Continue reading ‘Windows 常用网络命令’ »

Inspection of UCS C240 Rack Mount Server

Major Hardware Components:

  • UCS Chassis & bundled HW components
    Single or Dual CPU, DIMM Sockets, SAS Expander, Embedded & Internal pluggable (Optional) RAID card.
  • Hard Drivers (SFF: small form factor; LFF: Large form factor);
    24 SFF Drivers with SAS Expander.
    16 SFF Drivers without Expander.
    12 LFF Drivers with SAS Expander.
  • DIMM Card & PCIe Cards;

UCS C240 M3

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