Dynamic IP NAT

IP Dynamic Network Address Translation:

Exemplifying in a simple way to understand NATING.

IP NAT – Dynamic – (Inside Global – Inside Local <<>> Outside Local – Outside Global)

Scenario & what we need to achieve:

i) Router (Facing Internet)
ii) Core Switch
iii) We need to configure a Workstation or Server configured with Static IP Address – Advertised Globally with Public IP Address on the Router facing Internet.
iv) Outside world can access server only with advertised Global IP Address, even the private subnet won’t be allowed to access from outside network.

Let’s go….Check out the doc..

Dynamic IP NAT Document with Design   Dynamic NAT By Waqas

FXS & FXO Ports (Interfaces)

Some clarification on FXO & FXS ports in respect to VOIP world.

FXS – (Foreign Exchange Station).
FXS is an RJ11 port that connects internally to an analog office phone or fax machine. Think of the “S” as meaning a station or a cubicle. Any FXS port is going to connect to an analog DEVICE and the cable from the port to the device will never leave the building.

FXO – (Foreign Exchange Office).
FXO a telephone signaling interface that receives POTS (plain old telephone service). Let’s put it this way, FXO is a port that will connect a device to an outside telephone line. Think “O” for “Outside”. Picture an RJ11 wall jack that connects to a box in your basement which is connected to the line from your house to the nearest telephone pole on your street. Any RJ11 port on a device that is headed towards that wall jack is an FXO port. It connects your device to the “outside” world or your local area telephone “office”.

Let’s Make Sense of FXS & FXO:

FXS ports are often used on ATA (Analog Telephone Adapters) such as the Linksys PAP2T or Grand stream HT502. The FXS port connects the analog telephone to the ATA which connects to the internet via a Router or modem. Some ATA’s also have an FXO port. This connects to the wall jack by the computer to provide failover. In this case, in the event of internet failure, you can still make telephone calls via the POTS line. Also, you can use the FXO port to make free local calls on your POTS line.
FXO ports are most often used on Gateways and PBX’s to support Failover or Fallback as mentioned above. Most critical phone systems should have a failover feature so phone calls or faxes may continue in the event of internet failure.

Definition by Cisco:

FXS and FXO Interfaces

• An FXS interface connects the router or access server to end-user equipment such as telephones, fax machines, or modems. The FXS interface supplies ring, voltage, and dial tone to the station and includes an RJ-11 connector for basic telephone equipment, keysets, and PBXs.

• An FXO interface is used for trunk, or tie line, connections to a PSTN CO or to a PBX that does not support E&M signaling (when local telecommunications authority permits). This interface is of value for off-premise station applications. A standard RJ-11 modular telephone cable connects the FXO voice interface card to the PSTN or PBX through a telephone wall outlet.

Routing & Switching LAB (Packet Tracer) including CME

Its a small but high level configuration to understand CME (Call Manager Express) works within small corporate with basic functionality, Dynamic routing configured between routers to exchange and learn shortest path to route voice or data traffic.

Packet Tracer Version 6.0.1 has been used, PKT file attached to see & simulate configuration.

Dropbox Link:

Following configured but not limited to:

Routers Configured as:

1. DHCP Pool for Voice & Data (Not All)
2. CME Configured with dial peer’s for call routing
3. Dynamic Routing IP OSPF
4. Complete Failover Design
5. Multi Layer Switches Trunked to pass Voice & Data Traffic
6. Access Switches to allow seperate Voice & Data Traffic to end nodes.
7. Some ML Switches allowed Voice VLAN for PoE Phones directly connected
8. All WAN interfaces configured with OSPF message digest md5 authentication.

Routing & Switching Design Packet Tracer

Fixing issues while Installing VMWare 5.5 on Desktop Dell Optiplex

Its a common issue to install VMWare ESXi 5.5 on Dell Optiplex, you may encounter an error “Network card not found”..

Use this helper to customize the ISO file to include the driver.

Download ESXi Customizer:  “V-Front will create custom image with”

Download this VIB file

It will replace existing Net-e1000e Version 1.1.2 with Version 2.1.4 and create custom ISO file.
Old Version:     net-e1000e-918739266.xml

Replaceing:      net-e1000e-9999999900.xml


  • Download the latest version of the ESXi-Customizer script
  • Run ESXi-Customizer.cmdfrom the installation directory.
  • A GUI will show up that lets you select the original VMware install-ISO, the customization file and a working directory for the script.

Customizer GUI

For TGZ files you can choose a repacking option: The default is Force repacking, because this is how older versions behaved, other choices are Do not touchand Force repacking and pause for advanced editing. Hover your mouse over these options to get tooltips displayed with information on their purposes.

  • Press the Run!-button to start the customization process.
  • The script will auto-detect the ESXi version.
  • If you try to customize an ESXi 4.1 media and you do not have administrative privileges or have UAC (User account control) enabled in Windows you will be prompted to allow the script to run with administrative access. Enter the credentials of an administrative user if needed and select Yes to continue.
  • The customized ISO file that is produced by the script will be stored in the working directory, together with a detailed log file (that is necessary for troubleshooting in case something goes wrong)
  • Please use the update check feature if possible to be informed about updates of this script.