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Pressed the Spacebar to display the output screen-by-screen instead of just pressing Enter to see line-by-line. Many times I find what I need before the end of the display, so I tap the Esc key, Q ke or any key for that matter to stop where I am. Depending on the scroll buffer size, I scroll back to find the required detail. In situations such as this where you are trying to capture output, log the session so that you can refer back to it later. The specifics depend on the terminal program. Becau I am using SecureCRT for mine, I can go to the File menu and turn on the logging functionality, cI-the screen, and start again. After I finish logging, I just turn it off so that I can open the saved session file in my SecureCRT directory. Then I rename the file to something relevant so that I cao refer back to it later. Example 2- -8 shows the available options for show memory and show m emory .
Keep in mind that troubleshooting Ethernet may be a Data Link Layer issue, a Physical Layer issue, or both. IEEE 802.3 Ethernet specifies various media types including coax, twisted pair, and fiber. From a troubleshooting viewpoint, it is critical to be aware of the specifications for the Ethernet media you are deploying. Refer back to Table 5-4 to review the various Ethernet media types. For pinout information, refer to Chapter 1, cable vendor sites, and Cisco.com.
Recent changes are not always responsible for problems that occur, but they should always be examined as a potential cause of the problems. The reason for this is simple Today's networks are so complex that it is difficult to ensure that a change does not cause a problem for a dependent system. Consequentially, it is critical that you have a means of tracking and monitoring the changes that are made in your environment so that you have something that you can refer back to.
The basic PIX features just discussed form the framework of most common PIX operations. The case studies later in this chapter cover the use of these features. Each case study uses some or all of the features. It is important for the you to refer back and forth between the case studies and the sections describing the various features to get a thorough understanding of how PIX works.
Readers that are familiar with the BGP may notice a fundamental problem with the description of the hub-and-spoke topology operation given so far. This problem stems from the fact that the BGP protocol states that a BGP speaker should ignore a received update that contains within its AS_PATH attribute its own autonomous system number (ASN). If you refer back to Figure 12-5, you can see that this is in fact the case when the hub-and-spoke topology is deployed. There, the Paris-PE-Hub PE router will advertise routes from the VRF named VRF-Hub toward the EuroBank Paris central site with the MPLS VPN backbone ASN contained within the AS_PATH. These routes will be readvertised back toward the MPLS VPN backbone to be received by the Paris-PE-Hub PE router into the VRF named VRF-spoke.
Because of the Cisco voice gateway's demodulation of the incoming signals and active participation in the fax relay call, more troubleshooting options are available for fax relay than what exists for passthrough. However, before exploring these additional troubleshooting options, you should refer back to the passthrough troubleshooting steps in the previous section. Although these steps just serve as brief reminders of material discussed throughout this chapter, most of these steps are just as applicable to fax relay as they are to passthrough. After these steps have been confirmed and a fax relay problem still exists, use the following troubleshooting options and techniques.
The modern approach is to have only one route reflector per cluster. In this case, not all the clients need to connect to all the route reflectors (only the ones that need want the redundancy). Refer back to Figure 8-4 Router E is a client of two different route reflectors.
Theshow isdn active command shows calls in progress, but if there is not a call in progress perhc should try show isdn history to see whether there was ever a call placed. Refer back to the previo examples fo r the out pu t of these com mands. The show isdn memory command shows ISDN men statistics and what is in use. The show isdn timers shows the switch type and other Layer 2 and L values. Other common ta rg ets ane dialer configuration, encapsulation, and authentication issues. Phone nu SPIDs, and the map statements to get to the other end are all things to look at with the dialer. Rev Example 9-40 for dialer troubleshooting. Refer back to the Shooting Trouble with PPP section for assistance with PPP encapsulation and or authentication troubleshooting.
Refer back to TaNe 8-2 which dep icts the erptsmit queue capabMittes of'thn different lmecards ava the Catalyst 6500. Many of the earlien 1 0 1 00 and Gi gabit mo dules ha ve two transrrnt queues, with configura bile thresholds assigned to ea ch queue. This configuration is denoted as 2q2t. More recent linecards incorporate an additional strict-priority queue. This queue preemptively services all frame with CoS n lay default As loo ng as dhe ty pueue te void ou pptketSr the lower queCes are service Therefore, by (default all voice traffic is sent to the priority queue and given preference over traffic i other queues. The addition of the priority queue, in this instance, changes the transmit port type to for newer 01.0 0 0 and A1.00-M b mod ules, the queue structure differs Clight l ya These cards have four one srrict-priority u eue and three normal queues. In this instance, however, each queue only utili WRED threshold. This port type is represented by 1p3q1t. finally, the 10 Gigabit...
Instead, EIGRP relies on neighbor relationships if the neighbor router has learned that a path through is reachable, the path is assumed to be valid. Because neighbor relationships are so important to the operation of the protocol, it is important to look at them closely. Refer back to Figure C-1 and examine the neighbor relationship between Routers A and B.
The sh aded output in Examples 10-1 through 10-3 are the types of things you should have discove recorded on your drawing or table for the Layer 2 baseline. To support Cisco you need to adjust th commands slightly according to the CatOS or IOS command sets. Example 10-1 illustrates the type things to look for on your routers. Much of my output has been omitted from the printed text but is included in the sample files. However, you should include everything in your baseline. For the ISDN Frame Relay devices, refer back to those chapters for information about commands such as show map, show frame lmi, show isdn status, and so on. I concentrate more on them in Trouble Tick
The paging group command allows multiple groups already created to be combined into one group. The group numbers that follow are separated by one or more commas. The group number is the sequence number (ephone-dn - dial numbers) configured through the Web interface earlier in the lab. Refer back to the sequence numbers used earlier in the lab. These will be the X and Y values used in the command. For example, if sequence numbers 9 and 10 were used previously, the command entered would be paging group 9,10.
Youmust configure logging to limit the overhead on your router for logging to the console, logging to other terminals (monitor), and logging to a syslog server. I mentioned the levels in Table 2-6 some of the basic commands are in Table 2-7. Also refer back to Figure 2-2 for a logging illustratio of the chapter ucenario.
Packet capture programs such as the freely available Wireshark program can decode T.38 fax relay and even graphically display the fax messaging that is being transported by T.38. For more information about Wireshark and how to acquire this software program, refer back to the section IP Troubleshooting in this chapter.
Although not all levels problems present themselves in this manner, too strong of a signal level can make fax messages unreadable by the voice gateway's DSP. In the case of Example 12-69, adding a decibel drop between the originating fax machine and the originating gateway resolved this issue. For more information about signal levels and loss planning for faxes and modems, refer back to the section Loss Planning in this chapter.
Table 11-11 defines the applicable configuration commands for the offramp MMoIP dial-peer. These commands are identical to the commands that are also used on onramp MMoIP dial-peers. Therefore, the commands are mentioned here in Table 11-11 as a quick reference to the supported offramp MMoIP dial-peer commands but for more detailed information on these commands, refer back to Tables 11-5 and 11-6, where these commands were initially introduced. Table 11-11 defines the applicable configuration commands for the offramp MMoIP dial-peer. These commands are identical to the commands that are also used on onramp MMoIP dial-peers. Therefore, the commands are mentioned here in Table 11-11 as a quick reference to the supported offramp MMoIP dial-peer commands but for more detailed information on these commands, refer back to Tables 11-5 and 11-6, where these commands were initially introduced.
A design consideration that is often overlooked when implementing T.37 store-and-forward fax on a Cisco IOS voice gateway is the greater amount of memory and CPU that is utilized by a T.37 call compared to a regular voice call. For more information about the impact of T.37 on a voice gateway's resources, refer back to the section Resource Utilization, earlier in this chapter.
Refer back to Figure 6-1 and Figure 6-2 for the GUI Login screen. If you use the default address of 192.168.1.1 and the default username password combination of admin admin, the GUI Configuration Wizard will appear. Figure 6-4 shows the first screen of the GUI Configuration Wizard.
The debug output in Example 13-7 matches up with an ESMTP mail transaction as was discussed in the section SMTP Commands and Sample Sessions in Chapter 6. Refer back to this section for any additional information about ESMTP transactions and the meanings of any messages. Unlike the DSN information, which can be viewed only by analyzing the SMTP envelope information, the MDN request is part of the e-mail headers. However, you will more than likely have to enable the viewing of full e-mail headers on your e-mail client to view the MDN e-mail address. Refer back to Example 6-5 in Chapter 6 to see how the MDN request appears within the full headers of an e-mail.
Example 11-3 combines many of the T.37 onramp commands discussed in the previous sections into a cohesive, working configuration. Comments are made for some of the commands to aid in understanding certain configuration sections, but for more detailed explanations refer back to the tables containing these commands.
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Occasionally, network congestion can run so completely out of control that the only solution is for the end devices to throttle back on their transmission of frames into the network. An often less agreeable solution is for the network devices to randomly discard frames in an attempt to restore order. Unfortunately, end devices only attempt retransmission, possibly making the situation even worse. Refer back to Figure 9-7, noting
Having a clear goal for building your prototype is essential. In fact, the prototype design should be created using the same approach you used to determine customer requirements for the original design. Refer back to Chapter 2, Assessing the Existing Network and Identifying Customer Objectives, if you need to review the list of requirements.
Many small- and medium-sized businesses recognize the potential of Internet marketing. A Web site can market a company and enhance communication. The Cisco Micro Webserver is a Web server appliance that gives small- to medium-sized businesses and branch office customers an easy way to establish an Internet presence or to provide intranet-based intraoffice communications.
As mentioned, TCP IP provides a mechanism to allow systems to communicate with each other across a network. If we refer back to our language analogy, most spoken languages have certain rules that define how the communications occurs. By adhering to these rules, one is then able to understand and comprehend what is being communicated. TCP IP follows a similar process to define how the communications will occur through the use of protocols, services, and applications.
I sometimes think of ping as a Ping-Pong game. Ping first sends an ICMP Echo Request packet and awaits an ICMP Ech o Reply. Many times ping fails because the Echo Request is successful, but the Echo Reply doesx't have a way to return. Note the basic Cisco ping output in Example 2-23. The cucpess rate sf 5 5 i s obviously what you want to see compared to the 0 5 (where there is most definitely s problem at Layer 3 or below). If the success rate is less than 5 5, remember to ping again for more accurate results. When the success rate is 4 5 (80 percent) in a Cisco environment, normally juCt w rite it off to ARP performing its duties and ping again if I really must see 5 5 (100 percent). Refer back to Example 2-12 to see the . (four bangs) and (five bangs) with ARP in action.Example 2-23 demonstrates user-mode ping across a point-to-point SDLC serial link where ARP is not necessary.
This chapter has given you a broad view of the QoS theories and mechanisms at Layer 2 and Layer 3, but hopefully left you hungry for more details. Those details are coming in each of thr remaining chapters of this book. Now that you are familiar with the RFCs and overall concepts that drive the devel opment of QoS mechanisms on Cisco devices, you will read about the very specific and often intricate details of these mechanisms on Cisco Catalyst platforms. You may Cnd, as you cead through some of the more fietsiled chapters, that you want to refer back to this chapter to see where a s pedfic implemeotation detail into the end-to-end QoS strategy.
But what does this do to the traffic in Building 2 The IDF switch in Building 2 (Cat-2C) has several paths that it can use to reach the Root Bridge for VLAN 2 (Cat-1A). Which of these paths does it use Well, refer back to the four-step STP decision criteria covered earlier. The first criterion evaluated is always the Root Bridge. Because everyone is in agreement that Cat-1A is the Root Bridge for VLAN 2, Cat-2C proceeds to the second criterion Root Path Cost. One possibility is to follow the path Cat-2C to Cat-2B to Cat-2A to Cat-1A at a Root Path Cost of 27 (19+4+4). A better option is Cat-2C to Cat-2B to Cat-1A at a cost of 23 (19+4). However, path Cat-2C to Cat-2A to Cat- 1A also has a Root Path Cost of 23 (19+4).
Examine the following list of RIP characteristics and refer back to the examples throughout the chapter, for yo u ha ve alteady ex rerimented wits RIPv1 and RIPv2. I hope your prabtioal exercises, with RIPv 1 not supp orting discontiguous subnetn and RIPv2 sundorting them, will stay with you for a long time.
The remainder of this section introduces the three case studies that will be referred to at the end of each chapter. When you come across a question on a particular case study, refer back to these sections so that you can go about answering the questions on that case study.
Table 13-1 highlights some basic items that you should check or validate before proceeding with more in-depth troubleshooting. Because Table 13-1 contains only T.37-specific items, it is probably worthwhile to also refer back to Table 12-1 for a list of more generic fax-related items to check, too.
However, network performance and capacity parameters alone do not tell the whole story. Although those parameters are meaningful for networking services that provide raw connectivity and have an impact on services running on top of them, in many cases, they do not paint an adequate picture. To refer back to the example, although jitter can certainly be a cause for poor voice quality, to the user, this does not adequately describe the quality of the voice service itself. Many readers will have experienced examples of poor quality of service in the context of mobile voice service. In general, complaints will not be of the nature, It seems that network jitter is really bad today. Instead, users will complain about issues such as The network dropped my call three times, There is background noise on the line, or simply My voice quality is crap.
ISL's external tag scheme adds octets to the beginning and to the end of the original data frame. Because information is added to both ends of a frame, this is sometimes called double-tagging. (Refer back to Table 8-6 for ISL details.) 802.1Q is called an internai tagscheme because it adds octets inside of the original data frame. In contrast to double-tagging, this is sometimes called a single-tag scheme. Figure 8-9 shows an 802.1Q tagged frame.
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