Understand
how WAN encapsulation types affect synchronous serial connections
Convert
from HDLC to PPP encapsulation on a WAN connection
Use
the terminology of the semester 4 online lesson on WANs.
Background:
This lab focuses on PPP
(Point-to-Point Protocol). PPP is a Wide Area Network (WAN) protocol
that provides OSI layer 2 (data-link layer) services for
router-to-router and host-to-network connections (over synchronous
and asynchronous circuits) using a serial interface. It is commonly
used by PCs to connect to an Internet Service Provider (ISP) via a
dial-up phone line (asynchronous host-to network) or as a WAN
encapsulation method between LANs (synchronous router-to-router).
PPP is an international, standardized and widely used protocol
developed by the Internet Engineering Task Force (IETF). PPP is
considered a part of the TCP/IP protocol suite and supports a number
of LAN protocols such as IP and IPX and various methods of security
authentication such as PAP and CHAP. PPP can be used on various
physical media, including twisted pair, fiber or satellite
transmission. It uses a variation of High-Speed Data Link Control (HDLC)
for packet encapsulation.
Synchronous Serial Ports:
Nearly all Wide Area Network (WAN) links used with
Internetwoks are "serial" meaning they transmit bits one
after another in a series along a wire or fiber cable. Routers have
Synchronous serial ports for WAN connections. They are not the same
as the Asynchronous serial connection ports found on PCs and are
capable of much higher data rates. Most routers have at least one
Synchronous serial port for WAN connection and two Asynchronous
serial ports; a Console port for local connection and an AUX port
for remote configuration of the router.
The Wide Area Network connections
between the routers in the standard Cisco lab setup are synchronous
serial links. Speeds for serial digital WAN links can range from a
56Kbps circuit to a T1 (appx. 1.5 Mbps) or a T3 (appx. 45 Mbps).
When setting up the serial WAN links for the router lab, the default
layer 2 encapsulation is a Cisco proprietary version of High-Level
Data Link Control (HDLC) protocol. PPP is more standardized,
providing better security and support for dialup connections. With
this lab you will convert the WAN links between the lab routers from
HDLC to PPP. The PPP encapsulation must be set on both ends of the
WAN connection.
Tools /
Preparation:
Prior to starting the lab, the
teacher or lab assistant should have the standard router lab with
all 5 routers set up. Before beginning this lab you should read the
Networking Academy Second Year Companion Guide, Chapter 10 on PPP.
You should also review the Semester 4 On-line chapter on PPP. Work
individually or in teams. The following is a list of resources
required.
Standard Cisco 5-router lab setup
with hubs and switches
2 routers with WAN link between
them and HDLC encapsulation (default)
Workstation connected to the
router's console port
Select a pair of routers which have a
WAN serial link between them such as Lab-A and Lab-B before starting
the lab. You could also use Lab-B and Lab-C or Lab-C and Lab-D.
Connect your workstation to the console port connection of the first
router (Lab-A).
Step 1 - Use the lab
diagram and show running-config command to answer the following
questions about the Lab-A router:
Lab-A# show running-config
Which Serial interface is used for
the WAN link?
What is the IP address of this
interface?
What is the subnet mask of this
interface?
Is this interface a DCE or DTE
connection?
How do you know if it is DCE or DTE?
What is the clock rate set for this interface?
What is the bandwidth set for
this interface (if set)?
What would the bandwidth be set to
if this were a T1 interface?
Step 2 - Examine the
WAN cables attached to Router Lab-A and answer the following
questions:
Which interface is the cable attached to on Router Lab-A?
What type of physical connector
connects to the serial port on the router?
What type of physical connector is
on the other end of the cable?
Step 3- Use the show interface command and
answer the following questions:
Lab-A# show interface serial 0
What is the status of the interface and the Line protocol?
How is the IP address and Subnet mask displayed?
What is the Maximum Transmission Unit (MTU)?
What is the bandwidth set to?
What is the purpose of setting the bandwidth?
(Hint: Function of a router)
What is the encapsulation currently set to?
Step 4 - Remove
the bandwidth setting from Serial S0 with the following series of
commands:
Lab-A# config t
Lab-A(config)# int s0
Lab-A(config-if)# no bandwidth
Use the
show interface s0
command again. What is default bandwidth
set to now?
Why do you think this is?
Change the bandwidth back to 56 Kbits with the following series of
commands:
Lab-A# config t
Lab-A(config)# int s0
Lab-A(config-if)# bandwidth 56
Use the show interface s0 command again to verify that the bandwidth
has been changed.
Step 5 - Use the show
cdp neighbors command and answer the following questions
Lab-A# show cdp neighbors
What is the device ID of the neighboring router?
What is the Local Interface that this device was discovered on?
What is the capability of the device?
What model platform number is it?
What is the Port ID for the neighboring router interface?
Step 6 - Check
Configuration of the WAN Interface on Router Lab-B
Telnet from Router Lab-A to Router Lab-B
and use the lab diagram and the show running-config command to answer the
following questions (either telnet to the router name or the IP address of
the Serial interface):
Lab-B# show running-config
Which Serial interface is used for the WAN link?
What is the IP address of this interface?
What is the subnet mask of this interface?
Is this interface a DCE or DTE connection?
How do you know if it is DCE or DTE?
What is the clock rate set to for this interface?
What is the bandwidth set for this interface?
Step 7 - Examine the WAN cables attached to Router Lab-B and answer the
following questions:
What interface is the cable attached to on Router Lab-B?
What type of physical connector is the Serial port on the router?
What type of physical connector is on the other end of the cable?
Step 8 - Use the show
interface command and answer the following questions:
Lab-B# show interface serial 1
What is the status of the interface and the Line protocol?
How is the IP address and Subnet mask shown?
What is the Maximum Transmission Unit (MTU)?
What is the bandwidth set to?
What is the encapsulation currently set to?
Step 9 - Use
the show cdp neighbors command and answer the following questions
Lab-B# show cdp neighbours
What is the device ID of the neighboring router?
What is the Local Interface that this device was discovered on?
What is the capability of the device?
What model platform number is it?
What is the Port ID for the neighboring router interface?
Step 10 - Change
the WAN Encapsulation on Router Lab-A from HDLC to PPP
Connect your workstation to the console port connection on Router Lab-A
and use the following commands to change the WAN encapsulation on Router
Lab-A Serial Interface 0 and answer the following questions:
Lab-A(config)# interface serial 0
Lab-A(config-if)# encapsulation ppp
Use the
show interface s0
command. What is the status of the interface and the Line protocol now?
What does this mean?
What was the encapsulation previously set to?
What is the encapsulation now set to now?
Can you Ping or Telnet from router Lab-A to router Lab-B?
Why or why not?
Step 11 - Change the WAN Encapsulation on
Router Lab-B from HDLC to PPP
Connect your workstation to the console port connection on Router
Lab-B (since you can no longer telnet to it) and use the following
commands to change the WAN encapsulation to on Router Lab-B Serial
Interface 1 and answer the following questions:
Lab-B# config t
Lab-B(config)# interface serial 1
Lab-B(config-if)# encapsulation ppp
Use the
show interface s1
command. What is the status of the
interface and the Line protocol now?