1. CCNA Guide to Cisco Networking
Chapter 11: PPP and ISDN

2. CCNA Guide to Cisco Networking
Objectives
Describe PPP encapsulation
Configure PPP encapsulation and its options
Describe and enable PPP multilink
Explain how to implement ISDN BRI on Cisco routers
Configure an ISDN BRI connection
CCNA Guide to Cisco Networking

3. CCNA Guide to Cisco Networking
PPP
Internet standard protocol
Considered a peer technology
Used over dial-up or leased lines
Support for multiple Network layer protocols
Most widely use WAN connection protocol
CCNA Guide to Cisco Networking

4. CCNA Guide to Cisco Networking
PPP (continued)
SLIP
Supports
Encryption
Compression
Error correction
Works with synchronous and asynchronous connections
Can be applied on many different physical interfaces
Asynchronous serial
ISDN synchronous
High-Speed Serial Interface (HSSI)
CCNA Guide to Cisco Networking

5. PPP In The Protocol Stack
Link control protocol
Data Link layer
Establish
Configure
Test
Network control protocols (NCPs)
Allows multiple protocols to used at the same time
IP control protocol (IPCP)
IPX control protocol (IPXCP)
AppleTalk control protocol (ATCP)
CCNA Guide to Cisco Networking

6. PPP In The Protocol Stack (continued)
CCNA Guide to Cisco Networking

7. CCNA Guide to Cisco Networking
Frame Format
CCNA Guide to Cisco Networking

8. Frame Format (continued)
Frame fields of PPP
Flag: Binary sequence , which indicates the beginning of the frame
Address: Binary sequence ; because PPP is used to create a point-to- point connection, there is no need for PPP to assign an individual address for each host
Control: Binary sequence , which indicates that the transmission of user data will not be sequenced and is to be delivered over a connectionless link
Protocol: Two bytes used to identify the protocol that is encapsulated
CCNA Guide to Cisco Networking

9. Frame Format (continued)
Frame fields of PPP (continued)
LCP or Data: The LCP field is also known as the Data field, which is the location contains the LCP information and the data that has been encapsulated from the higher layers
Frame Check Sequence (FCS): Cyclical redundancy check (CRC) to verify the integrity of the frame
Flag: Binary sequence , which identifies the end of the data frame
CCNA Guide to Cisco Networking

10. CCNA Guide to Cisco Networking
LCP
LCP field of the PPP packet may include
Asynchronous character map
Maximum receive unit size
Compression
Authentication
PAP
CHAP
Magic number
Link quality monitoring (LQM)
Multilink
CCNA Guide to Cisco Networking

11. LCP Link Configuration
LCP link configuration process includes
Link establishment
Authentication (optional)
Link-quality determination (optional)
Network layer protocol configuration negotiation
Link termination
CCNA Guide to Cisco Networking

12. Establishing PPP Communications
Link establishment phase
First phase
Testing and configuration of the data link
Second phase
Optional authentication
PAP and CHAP
Third phase
Network layer protocol configuration negotiation
Data packet transfer may begin
CCNA Guide to Cisco Networking

13. Establishing PPP Communications (continued)
CCNA Guide to Cisco Networking

14. Configuring PPP Authentication
Configure PPP authentication on each PPP host
Link flapping will occur if authentication is only on one host
PAP
Two-way handshake
Usernames and Passwords sent in clear text
CHAP
Three-way handshake
Usernames and passwords are protected
CCNA Guide to Cisco Networking

15. Configuring PPP Authentication (continued)
CCNA Guide to Cisco Networking

16. Configuring PPP Authentication (continued)
CCNA Guide to Cisco Networking

17. Configuring PPP Authentication (continued)
CCNA Guide to Cisco Networking

18. Confirming PPP Communications
“show interface” command
Router# show interface serial 0/0
CCNA Guide to Cisco Networking

19. CCNA Guide to Cisco Networking
ISDN
Circuit-switched service
Existing telephone service
Data
Voice
Video
Audio transmission
Faster than traditional modem speeds
CCNA Guide to Cisco Networking

20. CCNA Guide to Cisco Networking
ISDN (continued)
Basic Rate Interface (BRI)
128 kbps total data transfer bandwidth
2 B-channels
Bearer channel for data transfer
64 kbps
1 D-channel
Delta or data channel for signaling
Out of band signaling
Link Access Procedure-D
16 kbps
CCNA Guide to Cisco Networking

21. CCNA Guide to Cisco Networking
ISDN (continued)
Primary Rate Interface (PRI)
1.544 mbps total data transfer bandwidth
23 B-channels
Bearer channel for data transfer
64 kbps
1 D-channel
Delta or data channel for signaling
Out of band signaling
Link Access Procedure-D
CCNA Guide to Cisco Networking

22. CCNA Guide to Cisco Networking
ISDN (continued)
CCNA Guide to Cisco Networking

23. CCNA Guide to Cisco Networking
ISDN Standards
CCNA Guide to Cisco Networking

24. CCNA Guide to Cisco Networking
ISDN Operations
CCNA Guide to Cisco Networking

25. ISDN Operations (continued)
Functions and references
Function groups
Terminal adapter
Terminal equipment 1 (TE1)
Terminal equipment 2 (TE2)
Network termination 1 (NT1)
Network termination 2 (NT2)
CCNA Guide to Cisco Networking

26. ISDN Operations (continued)
Functions and references (continued)
Reference points
U: Demarc between client and telco
R: Point between non-ISDN equipment (TE2) and TA
S: Point between customer’s TE1 or TA and the network termination (NT1 or NT2)
T: Point between a NT1 and a NT2
S/T: Point between TA and NT1 in the absence of a NT2
CCNA Guide to Cisco Networking

27. CCNA Guide to Cisco Networking
SPID
Connect to service provider switch
Service Profile Identifier (SPIDs)
Dial-in access
ISDN phone numbers
Provide a profile
Service level agreement
AutoSPID
CCNA Guide to Cisco Networking

28. CCNA Guide to Cisco Networking
SPID (continued)
Service provider switch types
dms-100: Northern Telecom DMS-100 (as previously described)
ni1: National ISDN-1; used in North America
net3: Net3 switch; used in Europe and the United Kingdom
ntt: Switch from NTT; used in Japan
1tr6: 1TR6 switch; used in Germany
ts013:TS013 Australian switch
none: Used when a switch has not been specified
CCNA Guide to Cisco Networking

29. CCNA Guide to Cisco Networking
SPID (continued)
CCNA Guide to Cisco Networking

30. CCNA Guide to Cisco Networking
Multilink PPP
Combine the bandwidth of individual links or channels
Multilink provides
Load balancing
Packet fragmentation and reassembly
Sequencing for packets
Creates one logical connection
Function over synchronous or asynchronous connections
Router(config-if)# ppp multilink
CCNA Guide to Cisco Networking

31. CCNA Guide to Cisco Networking
DDR
Dial-on-demand routing (DDR)
Intermittent WAN access
Saves money on metered lines
Used with circuit switched access
Define interesting traffic
Common configuration commands
“dialer-list” command
“dialer-group” command
“access-list” command
CCNA Guide to Cisco Networking

32. CCNA Guide to Cisco Networking
DDR (continued)
CCNA Guide to Cisco Networking

33. CCNA Guide to Cisco Networking
DDR (continued)
CCNA Guide to Cisco Networking

34. ISDN BRI Configuration Examples
CCNA Guide to Cisco Networking

35. ISDN BRI Configuration Examples (continued)
Dialer profiles
Scalable compared to legacy DDR
Configuration of dialer profiles involves
Dialer interface
Logical configuration
Dial string for each destination subnet
Dialer map class
Optional commands
Define characteristics for each call
Dialer pool
Identify the physical interface that will be used by the dialer interface
CCNA Guide to Cisco Networking

36. ISDN BRI Configuration Examples (continued)
CCNA Guide to Cisco Networking

37. CCNA Guide to Cisco Networking
Monitoring ISDN
ISDN problems are often associated with
PPP configuration
“debug ppp authentication”
“debug ppp negotiation”
“clear interface”
Dialer configurations
“show dialer”
“show interface”
“debug dialer”
ISDN monitoring commands
“show isdn status”
“show interface bri 0”
“debug q921”
CCNA Guide to Cisco Networking

38. CCNA Guide to Cisco Networking
Digital Lines
T1: 24-channel, mbps
T1C: 48-channel, mbps
T2: 96-channel, mbps
T3: 672-channel, mbps
T4: 4032-channel, mbps
E1: 30-channel, mbps
Fractional T1 or E1
Digital Subscriber Line (DSL)
CCNA Guide to Cisco Networking

39. CCNA Guide to Cisco Networking
Summary
Many WAN connectivity options are available for modern networks, including digital lines, Frame Relay, and analog modems
WAN technologies typically define Data Link and Physical layer standards
The Point-to-Point Protocol (PPP) is the most widely used WAN protocol today
On Cisco routers, PPP is used mainly as a Data Link layer encapsulation method; however, it does provide an interface to the Network layer via specific Network Control Protocols (NCPs)
CCNA Guide to Cisco Networking

40. CCNA Guide to Cisco Networking
Summary (continued)
PPP provides link establishment, quality determination, Network layer protocol encapsulation, and link termination services
PPP is often used over Integrated Services Digital Network (ISDN) connections
ISDN is a digital service provided by several telecommunications companies worldwide
ISDN was developed as a faster WAN connection to replace analog modems, and as a cheaper alternative to Frame Relay and full T1 connections
ISDN service comes in Basic Rate Interface (BRI) and Primary Rate Interface (PRI)
CCNA Guide to Cisco Networking

41. CCNA Guide to Cisco Networking
Summary (continued)
BRI offers connections of up to 128 Kbps for data transfer, and PRI offers up to 24 channels in the United States, each with the ability to transfer data at 64 Kbps
Connections over ISDN can take advantage of dial-on-demand routing (DDR) and multilink services offered through PPP connections
DDR allows the router using an ISDN connection to dial only when there is interesting traffic and to add more channels as needed to support given traffic levels
DDR can be implemented using dialer profiles, which allow more flexibility regarding the calling parameters
Multilink allows ISDN to use multiple channels evenly by spreading the load across those channels
CCNA Guide to Cisco Networking