Bambang F. Indarto

The Journey… The Shares

Posts Tagged ‘Server’

Configure Your Router As DHCP Server

Posted by bfindarto on March 30, 2008

Well.. if you have situation like: you have 20 to 100 clients, and you don’t have a DHCP server (becouse of your company doesn’t want waste money for buying a Server? he he..), you may configure your router as the DHCP server for the networks. Okay, here we go:

1. Define a DHCP address pool
MyRouter(config)#ip dhcp pool network-address subnet-mask
you may replace subnet mask number with /prefix or the CIDR number

2. Configure Basic Parameters
a. Router(dhcp-config)#default-router ip-address (usually the the network gateway’s ip address on router’s interface)
b. Router(dhcp-config)#Network first-ip-address last-ip-address

3. Configure Additonal Parameters
a. Router(dhcp-config)#dns-server dns-server-ip-address
b. Router(dhcp-config)#netbios-name-server net-bios-server-ip-address
c. Router(dhcp-config)#domain-name NAME
d. Router(dhcp-config)#lease DAYS HOURS MINUTES or
e. Router(dhcp-config)#lease infinite

4. Configure the IP addresses to be excluded from the pool
This is usually done to avoid the conflicts caused by the DHCP with servers and printers. Remember to give ALL servers and network printers static IP addresses in the same range of the DHCP pool. And then exclude these addresses from the pool to avoid conflicts.

Router(config)#ip dhcp excluded-address ip-address (repeat this as many static ip addresses you have to exclude it from the pool, or
Router(config)#ip dhcp excluded-address start-ip-address end-ip-address

5. Enable the DHCP service in the router
Router(config)#service dhcp
To disable it use
Router(config)#no service dhcp

Usually the DHCP service is enabled by default on your router.

6. Verify your DHCP configuration
Router#show ip dhcp binding
Router#show ip dhcp server statistics
Router#debug ip dhcp server

DHCP server software is supported for these series; 800, 1000, 1400, 1600, 1700 series (Cisco IOS Release 12.0[2]T), 2500, 2600, 3600, 3800, MC3810, 4000, AS5100, AS5200, AS5300, 7000, 7100, 7200, MGX 8800 with an installed Route Processor Module, 12000, uBR900, uBR7200, Catalyst 5000 family switches with an installed Route Switch Module, Catalyst 6000 family switches with an installed MultiLayer Switch Feature Card, and Catalyst 8500.


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WAN Protocols: HDLC, PPP, and Frame Relay

Posted by bfindarto on March 26, 2008


HDLC stands for High-Level Data Link Control protocol. Like the two other WAN protocols (PPP and Frame Relay), HDLC is a Layer 2 protocol (see OSI Model for more information on Layers). HDLC is a simple protocol used to connect point to point serial devices. For example, you have point to point leased line connecting two locations, in two different cities. HDLC would be the protocol with the least amount of configuration required to connect these two locations. HDLC would be running over the WAN, between the two locations. Each router would be de-encapsulating HDLC and turning dropping it off on the LAN.

HDLC performs error correction, just like Ethernet. Cisco’s version of HDLC is actually proprietary because they added a protocol type field. Thus, Cisco HDLC can only work with other Cisco devices.

hdlc.jpgHDLC is actually the default protocol on all Cisco serial interfaces. If you try to a show running-config on a Cisco router, your serial interfaces (by default) won’t have any encapsulation. This is because they are configured to the default of HDLC. If you do a show interface serial 0/0/0, you’ll see that you are running HDLC.


You may have heard of the Point to Point Protocol (PPP) because it is used for most every dial up connection to the Internet. PPP is documented in RFC 1661. PPP is based on HDLC and is very similar. Both work well to connect point to point leased lines.

The differences between PPP and HDLC are:

  • PPP is not proprietary when used on a Cisco router
  • PPP has several sub-protocols that make it function.
  • PPP is feature-rich with dial up networking features

Because PPP has so many dial-up networking features, it has become the most popular dial up networking protocol in use today. Here are some of the dial-up networking features it offers:

  • Link quality management monitors the quality of the dial-up link and how many errors have been taken. It can bring the link down if the link is receiving too many errors.
  • Multilink can bring up multiple PPP dialup links and bond them together to function as one.
  • Authentication is supported with PAP and CHAP. These protocols take your username and password to ensure that you are allowed access to the network you are dialing in to.

To change from HDLC to PPP, on a Cisco router, use the encapsulation ppp command. After changing the encapsulation to ppp, typed ppp ? to list the PPP options available. There are many PPP options when compared to HDLC. 


Frame Relay is a Layer 2 protocol and commonly known as a service from carriers. For example, people will say “I ordered a frame-relay circuit”. Frame relay creates a private network through a carrier’s network. This is done with permanent virtual circuits (PVC). A PVC is a connection from one site, to another site, through the carrier’s network. This is really just a configuration entry that a carrier makes on their frame relay switches.

Obtaining a frame-relay circuit is done by ordering a T1 or fractional T1 from the carrier. On top of that, you order a frame-relay port, matching the size of the circuit you ordered. Finally, you order a PVC that connects your frame relay port to another of your ports inside the network.

The benefits to frame-relay are:

  • Ability to have a single circuit that connects to the “frame relay cloud” and gain access to all other sites (as long as you have PVCs). As the number of locations grow, you would save more and more money because you don’t need as many circuits as you would if you were trying to fully-mesh your network with point to point leased lines.
  • Improved disaster recovery because all you have to do is to order a single circuit to the cloud and PVC’s to gain access to all remote sites.
  • By using the PVCs, you can design your WAN however you want. Meaning, you define what sites have direct connections to other sites and you only pay the small monthly PVC fee for each connection.

Some other terms you should know, concerning frame relay are:

LMI = local management interface. LMI is the management protocol of frame relay. LMI is sent between the frame relay switches and routers to communicate what DLCI’s are available and if there is congestion in the network.

DLCI = data link connection identifier. This is a number used to identify each PVC in the frame relay network.

CIR = committed information rate. This is the amount bandwidth you pay to guarantee you will receive, on each PVC. Generally you have much less CIR than you have port speed. You can, of course, burst above your CIR to your port speed but that traffic is marked DE.

DE = discard eligible. Traffic marked DE (that was above your CIR) CAN be discarded by the frame-relay network if there is congestion.

FECN & BECN = forward explicit congestion notification & backward explicit congestion notification. These are bits set inside LMI packets to alert the frame-relay devices that there is congestion in the network.

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Want to be CCNA? Prepare Yourself here..

Posted by bfindarto on March 13, 2008

The CCNA certification is a valuable certification that is frequently updated, so there are about 5 things that every CCNA candidates should have handy when preparing for the CCNA or trying to keep your CCNA current. Lets take a look…

Look out for new changes to the CCNA certification program!

There are frequently new changes to the CCNA certification (as well as the other Cisco certifications). For example, on June 25, 2007, Cisco introduced the Cisco Certified Entry-Level Network Technician (CCENT). There is a 640-822 exam that you must pass to achieve the CCENT certification. Cisco has broken up the Interconnecting Cisco Network Devices (ICND) one week training into two weeks and has named them ICND Part 1 and ICND Part 2. ICND Part 1 is to prepare you for the CCENT certification and ICND part 2 is to prepare you for the CCNA certification. To pass the CCNA, you can take ONE of the following paths:
ICND1 640-822 and ICND2 640-816, or
CCNA 640-802 composite exam
For more information on Cisco certification program updates, checkout the Cisco Learning Program updates website.

Important Websites to help you prepare for the CCNA certification.

I have used some excellent FREE resources for CCNA-related training, preparation, and question/answer. Here is my list:
Cisco’s CCNA Prep Center
Cisco’s official CCNA certification home

Important Technical Tips to passing your CCNA

Here are my important tips to passing the CCNA the first time:
Know what is on the Exam – for example, if you are taking the 640-802 exam, you should know the 640-802 exam blueprint front and back. You should be able to talk at length about these topics.
Know the basics of getting around and configuring a real router – you can’t count on just books to get you through the exam. You should find some way to get on a real router (borrow, buy, or get yourself on the training, he he.. 🙂 ) or a simulator (PacketTracer, or Boson Simulator). The test will give you a simulated router and you will have to do something on it. If you have never used one before, you will be in trouble.
Know how to perform IP subnetting and also number system conversioncoz this is where all the problems come 🙂 .

The Value of a CCNA certification
According to the salary surveys, an IT professional who has a CCNA earns, on average, $76,500 USD. That is $16,500 more than the $60,000 average rate earned by CCNAs in 2004. Even better, if you could upgrade your CCNA to a CCNP, you could earn an average estimated $12,000 per year more (that is $1,000 per month).

Keep in mind the IT Pro’s surveyed may have multiple years of experience and/or other certifications. For example, from those surveyed who have ONLY a CCNA, the average salary is $68,000.So, in general, what are these numbers telling you?The value of a CCNA continues to increase. You can justify a higher salary by having a CCNA. The more years of experience you have and the more certifications you have, the more salary you will be awarded (on average, of course). To some of you, this may be obvious information. To others this may be “news”. Either way, the survey helps to justify cost and time associated with obtaining your CCNA.

The single source for the best CCNA and CCNP video training available

In my opinion, the single best source I have seen for CCNA & CCNP training material is the Train Signal CCNA video training series covering these exams. These videos are the closest thing you can find to hands-on real world training. You get to see an expert-level network administrator not only train you on what you need to need to pass the exams but also train you on how to configure Cisco routers & switches for the real world.

In summary, the CCNA certification is a valuable certification that is frequently updated. You should use the websites found in this article to ensure you have what you need to pass the CCNA and, after that, stay current on the CCNA certification.

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