Frame Relay is a Layer 2 edge technology whereby frames travel from your routers (DTE devices) through a series of Frame Relay switches to get to the proper destination. At the edge of enterprise and service provider networks, these switches are DCE devices, although this varies within the clouds. Frame is one of those technologies that is not only available in the United States, but also worldwide. The service can be carrier provided or privately owned and is a cost- effective alternative to leased lines.
This chapter begins the WAN focus of this book with shooting Frame Relay troubles. It gives practical application to a number of objectives falling under the CCNP support guidelines and more. Use familiar Cisco commands and problem isolation techniques to build the chapter scenarios and resolve the Trouble Tickets. This chapter assumes you have a good understanding of protocol characteristics and a methodical troubleshooting mindset.
With supporting the WAN, many times the battle is deciding whether the problem is in fact yours or whether it is a service provider issue. You will analyze real-world Frame Relay issues including Layer 2 and Layer 3 addressing and issues related to LMI, data-link connection identifier (DLCI) assignments, mapping statements, routing protocols, and so on. Continue to identify targets and document the results using ping, trace, show, clear, debug, and other troubleshooting
commands and utilities. To gain practical experience, you may follow the many figures and examples in this chapter or use my guidelines to build it yourself.
This chapter covers the following topics:
Scenario: Shooting Trouble with Frame Relay A Brief History of Frame Relay
Frame Relay Frames Frame Relay Addressing
Frame Relay at the Physical Layer Shooting Trouble with Frame Relay Trouble Tickets
Trouble Ticket Solutions
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
Supporting Website Files
You can find files and links to utilities that support this book on the Cisco Press website at www.ciscopress.com/1587200570. Even if you do not have a lab, you can take advantage of the supporting configuration files including the logs to understand device input and output. The files are listed throughout the chapters in italics.
In order to be able to read and work with some of the supporting files offered at www.ciscopress.com/1587200570, you may want to download some of the programs listed in Table I-1 in the Introduction.
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
Scenario: Shooting Trouble with Frame Relay
In the WAN world, it is always easy to blame things on someone else. Therefore, it is important to understand a bit about what happens in the cloud and on the user ends so that you can narrow down the problem as to whether it is your problem, someone else's problem or a service provider issue. The goal in this first scenario is to configure Frame Relay in a hybrid back-to-back configuration using r1, r2, and r3, as in Figure 8-1.
Figure 8-1. Shooting Trouble with Frame Relay (Hybrid Back-to-Back Topology)
As always, there is not always one right or wrong way to achieve this task or tasks presented. The ability to obtain the end result using good practices is extremely important in any real-world network. My
troubleshooting and device configurations are presented starting in Example 8-1 so that you can compare your work and perhaps see a different approach to obtaining the end result. Use the previous checklists, your step- by-step troubleshooting methodology, and the Frame Relay checklist in Table 8-1 to assist in testing.
Table 8-1. Frame Relay Quick Troubleshooting Checklist
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
Isolating Problems Commands and
Symptoms Check IP address, subnet mask, and routing protocols. All of these are Layer 3 or above
that ride on top of Frame Relay. Keep in mind that many routing protocols are multicast/broadcast, but Frame Relay is NBMA[*].
ping traceroute show ip protocols show ip route
Isolating Problems Commands and
Symptoms Check interface status and encapsulation. If the point-to-point PVC[**] is active, for
example, line protocol for the subinterface is up.
show ip
interface brief show interfaces serial 0
Are you communicating with the provider? show frame-
relay lmi
Are your DLCIs active? show frame-
relay map show frame- relay pvc clear frame- relay-inarp
Look at PVC statistics. Monitor the Frame traffic. show frame-
relay traffic
Verify the route statements on the frame switch. show frame-
relay route
Watch the interface communications. debug serial
interface
Watch the LMI[ ] handshake. debug frame-
relay lmi
Watch the packets received. debug frame-
relay events
Watch the packets sent. debug frame-
relay packet
[*] NBMA = nonbroadcast multiaccess
[**] PVC = permanent virtual circuit
[ ] LMI = Local Management Interface
Back-to-Back Frame Relay
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
A Frame Relay back-to-back configuration can be quite helpful in a testing environment once you get it to work.
Refer to Cisco.com for assistance with a true back-to-back external link Frame Relay solution using no LMI. I want you to use sort of a hybrid back-to-back situation for testing where r2 acts as a pseudo frame switch as I do Example 8-1. It is a good idea to confirm that things are not broken to begin with if you are starting from existing configurations. Back-to-back frame is tricky enough, however, so I want you to erase the
configurations on the three routers and configure back-to-back frame from the beginning.
Configure the routers starting with r2 first because it is acting as a back-to-back hub device for the other routers (see Figure 8-1 and Example 8-1). For now just configure the bare-bones configuration with no
descriptions or passwords to concentrate on this Layer 2 technology in action. In a practical environment, this obviously should be a requirement.
Example 8-1. Configuring r2 as a Pseudo Frame Switch
Router(config)#hostname r2
r2(config)#frame-relay switching r2(config)#interface serial 0 r2(config-if)#bandwidth 64
r2(config-if)#ip address 192.168.5.9 255.255.255.252 r2(config-if)#encap frame-relay
r2(config-if)#frame-relay intf-type dce r2(config-if)#frame-relay local-dlci 108 r2(config-if)#no shut
r2(config-if)#interface serial 1 r2(config-if)#bandwidth 64
r2(config-if)#encap frame
r2(config-if)#ip address 192.168.5.6 255.255.255.252 r2(config-if)#encap frame
r2(config-if)#frame-relay intf-type dce r2(config-if)#frame-relay local-dlci 104 r2(config-if)#no shut
I called r2 a pseudo frame switch because there are no frame route statements in the configuration. The encap frame-relay command changed the default High-Level Data Link Control (HDLC) encapsulation on the WAN
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
interfaces to Frame Relay so that you could configure the other Frame Relay parameters. Now look at the frame map and PVCs in Example 8-2.
Example 8-2. Reviewing the Map and PVCs on the Frame Switch
r2#show frame-relay map r2#show frame-relay pvc
PVC Statistics for interface Serial0 (Frame Relay DCE)
DLCI = 108, DLCI USAGE = LOCAL, PVC STATUS = INACTIVE, INTERFACE = Serial0 input pkts 0 output pkts 0 in bytes 0
out bytes 0 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0
out bcast pkts 0 out bcast bytes 0
pvc create time 00:01:30, last time pvc status changed 00:00:53
PVC Statistics for interface Serial1 (Frame Relay DCE)
DLCI = 104, DLCI USAGE = LOCAL, PVC STATUS = INACTIVE, INTERFACE = Serial1 input pkts 0 output pkts 0 in bytes 0
out bytes 0 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0
out bcast pkts 0 out bcast bytes 0
pvc create time 00:00:31, last time pvc status changed 00:00:31 r2#copy running-config startup-config
It certainly makes sense that there is no frame mapping at this point because the other ends (r1 and r3) are still configured for HDLC encapsulation, the default for serial interfaces. For the same reason, the PVCs are inactive. The DLCIs were assigned on the main interface using the frame-relay local-dlci command. Typically the frame interface-dlci command is used when using subinterfaces with LMI provided (as discussed later in this chapter).
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
NOTE
From a support standpoint, it is good to see the bouncing PVC state from active to inactive, because for future reference you now know this is a good indication the other end of the PVC has not been configured.
It is important to note that regardless of the physical DTE/DCE cable, Frame Relay has its own DTE/DCE
configuration at Layer 2 as you witnessed with the frame-relay intf-type dce command for both interfaces on r2. If you issue the show controllers command as in Example 8-3, you will see that both are physical DTE interfaces. However, the preceding example portrays them as Frame Relay DCEs. This is absolutely correct. For there is a Layer 1 and Layer 2 DTE/DCE with this technology.
Example 8-3. show controllers for the Physical DTE
r2#show controllers s 0
HD unit 0, idb = 0x107EAC, driver structure at 0x10D340 buffer size 1524 HD unit 0, V.35 DTE cable
cpb = 0x1, eda = 0x48DC, cda = 0x48F0 RX ring with 16 entries at 0x4014800 ...
r2#show controllers s 1
HD unit 1, idb = 0x111648, driver structure at 0x116AE0 buffer size 1524 HD unit 1, V.35 DTE cable
cpb = 0x2, eda = 0x3104, cda = 0x3118
NOTE
On a practical note, generating clock is also a Layer 1 DCE function and Layer 2 is not concerned with clocking.
Next configure r1 to communicate to r2 using Frame Relay as in Example 8-4. Turn on debug service
• Table of Contents
• Index
CCNP Practical Studies: Troubleshooting By Donna L. Harrington
Publisher: Cisco Press Pub Date: April 04, 2003
ISBN: 1-58720-057-0 Pages: 840
Hands-on practice for the CCNP Troubleshooting exam with TCP/IP, LAN, and WAN trouble tickets based on Cisco Internetwork Troubleshooting (CIT) topics.
With this book, you can:
Set up and follow along with real-world lab scenarios aligned to each exam topic, with or without the actual equipment
Establish a baseline and document your physical and logical network
Identify troubleshooting targets using ping, trace, show, clear, debug, and other troubleshooting tools and utilities
Diagnose and troubleshoot actual problems by following along with author-provided Catalyst(r) OS and Cisco IOS(r) Software command input, output, and logging Use instructor-developed problem-isolation methods to resolve Trouble Tickets
"Sniff" the wire to spot network issues
Analyze local and remote access problems in Ethernet networks, including issues with cabling, speed and duplex, utilization and collisions, bandwidth, CSMA/CD, one-way link, auto negotiation, addressing, encapsulation, and more
Apply a layered troubleshooting methodology to real-life routing and switching environments
Designed for aspiring CCNP and CCIE(r) professionals, this indispensable lab guide builds on Cisco(r) Internetwork Troubleshooting (CIT) topics that prepare you for the CCNP
Troubleshooting exam. Full of practical exercises that get you ready for challenges on the job, CCNP Practical Studies: Troubleshooting gives you an edge over the competition through real- world application of LAN and WAN topics.
CCNP Practical Studies: Troubleshooting provides you with practical information on all the important concepts central to the troubleshooting portion of the CCNP certification, including
timestamps and logging. Clear the counters to make sure you start your troubleshooting from this point on if necessary. Feel free to turn on logging synchronous, too. Because this is a lab, just before you bring up the interface turn on keepalive debugging to watch the goings-on.
Example 8-4. Back-to-Back Frame Relay r1 Configuration
Router(config)#hostname r1
r1(config)#service timestamps debug datetime localtime msec r1(config)#service timestamps log datetime localtime msec r1(config)#exit
r1#clock set 5:21:00 Dec 9 2002 r1#clear counters
r1#configure terminal r1(config)#line console 0
r1(config-line)#logging synchronous r1(config-line)#interface s1
r1(config-if)#bandwidth 64 r1(config-if)#clock rate 64000
r1(config-if)#ip address 192.168.5.5 255.255.255.252 r1(config-if)#encap frame
r1(config-if)#end
r1#debug frame-relay lmi
Frame Relay LMI debugging is on Displaying all Frame Relay LMI data r1#configure terminal
r1(config)#interface s1 r1(config-if)#no shut
Dec 9 05:25:31.487: %LINK-3-UPDOWN: Interface Serial1, changed state to up Dec 9 05:25:31.527: Serial1(out): StEnq, myseq 1, yourseen 0, DTE up
Dec 9 05:25:31.531: datagramstart = 0xE22EA4, datagramsize = 14