CCIE за год. Цикл 7. Тема 42. Вопросы.

1) Объясните разницу между CoPP и CPPr
DescriptionCoPPCPPr
Levels of control plane filtering availableaggregateThree: subinterfaces (host, transit, CEF-exception)
Support for Distributed or Hardware Switching Platformsyesno
CEF requirednoyes
Provides a mechanism for dropping packets that are directed to closed or nonlistening TCP/UDP portsnoyes
Ability to enforce limits on the number of packets for a specified protocol that are allowed in the control plane IP input queuenoyes
2) Что произойдет с CoPP и CPPr при глобальном отключении cef

CPPr requires Cisco Express Forwarding (CEF). If CEF is not enabled, policies applied to the control plane subinterfaces will not be effective. However, CoPP policies applied directly to the control plane interface will be effective.

3) Что такое aggregate path для control plane

aggregate path = aggregate control-plane interface = CoPP

4) Какими способами можно фильтровать трафик предназначенный интерфейсу host. Описать каждый.

CoPP, port filtering, and per-protocol queue thresholding protection features can be applied on the control plane host subinterface.

5) На основании каких критериев допускается классифицировать трафик

standart and external ACL,
match ip dscp,
match ip precedence,
match protocol arp.

6) Куда можно применить политику в исходящем направлении

output policing — only on the aggregate control-plane interface

7) Какая команда покажет статистику по применненным политикам

show policy-map [type policy-type] control-plane [pfx | slot slot number] [all] [host | transit | cef-exception] [{input | output} [class class-name]]

8) Какой протокол можно использовать в «match protocol» для классификации в CoPP

ARP

CCIE за год. Цикл 7. Тема 41. Вопросы.

1. Дайте объяснение работе Event Detector

Event detectors monitor the operational state of processes on an IOS device. These processes run at medium priority, are always operational, and on detecting an event, the event detector sends an alert that provides information about the specific event.

2. Дайте объяснение работе Event Server

The EEM server is a bridge between the policies and internal Cisco IOS subsystems used within the event detectors. Some of the functionality of the EEM server is to register events seen in the IOS subsystems, store information about an event, publish an event, request additional information about an event, register internal script directories, register Tcl scripts and applets, and process actions taken by user-defined scripts. The version of EEM is based on the IOS release cycle. It is important to understand the functionality of EEM based on the IOS image, so that you fully understand the features and functionality of the event detectors and what is supported.

3. Приведите примеры Event Detector’ов

Application-Specific Event Detector
CLI Event Detector
Counter Event Detector
Custom CLI Event Detector
Enhanced Object Tracking Event Detector
GOLD Event Detector
Interface Counter Event Detector
IP SLA Event Detector
NetFlow Event Detector
None Event Detector
OIR Event Detector
Resource Event Detector
RF Event Detector
RPC Event Detector
Routing Event Detector
SNMP Event Detector
SNMP Notification Event Detector
SNMP Object Event Detector
Syslog Event Detector
System Manager Event Detector
Timer Event Detector
Watchdog System Monitor (IOSWDSysMon) Event Detector for Cisco IOS
Watchdog System Monitor (WDSysMon) Event Detector for Cisco IOS Software Modularity

4. Приведите названия частей из которых состоить EEM Applet

Three pieces of information in EEM applet:
First you will give (Applet Name) then you will decide what (Event Detector) will be used to detect specific event then finally what (Actions) you would like to automatically run once this event occur .

5. Где сохраняется EEM Applet

Configuration file

6. Опишите шаги создания EEM Applet

— event manager applet <name>
— event <event name>
— action <action>

7. Опишите шаги создания EEM TCL

— Event Register Keyword (required)
— Environment must defines
— Namespace Import
— Entry Status
— Body (required)

8. Дайте объяснение понятию Multi Event support

Function to allow much more control by being able to correlate multiple events to trigger actions. Up to 6 event statements can be used in an applet and up to 8 events can be used in a Tcl script, with support for Boolean functions. This capability provides a unique capability to assist in troubleshooting complex issues with multiple dependencies, as well as more robust methods of configuring and monitoring devices by correlating events together.

CCIE за год. Цикл 7. Тема 40. Вопросы.

1. Дайте объяснение header compression.

Header compression is a mechanism that compresses the header in a data packet before the packet is transmitted. Header compression reduces network overhead and speeds up the transmission of packets. Header compression also reduces the amount of bandwidth consumed when the packets are transmitted.

2. Какие виды header compression использует cisco.

TCP header compression
RTP header compression

3. Объясните принцип работы header compression в RTP

RTP header compression compresses the RTP header (that is, the combined IP, UDP, and RTP segments) in an RTP packet. RTP header compression identifies the RTP traffic and then compresses the IP header portion of the RTP packet. The IP header portion consists of an IP segment, a UDP segment, and an RTP segment. The minimal 20 bytes of the IP segment, combined with the 8 bytes of the UDP segment, and the 12 bytes of the RTP segment, create a 40-byte IP/UDP/RTP header. The RTP header portion is compressed from 40 bytes to approximately 5 bytes.
RTP header compression is supported on serial interfaces using Frame Relay, HDLC, or PPP encapsulation. It is also supported over ISDN interfaces.

4. Объясните работу Class-Based Header Compression в MQC

Class-based RTP and TCP header compression allows you to configure either RTP or TCP header compression for a specific class within a policy map (sometimes referred to as a traffic policy). You configure the class and the policy map by using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC). The MQC is a CLI that allows you to create classes within policy maps (traffic policies) and then attach the policy maps to interfaces (or subinterfaces). The policy maps are used to configure and apply specific QoS features (such as RTP or TCP header compression) to your network.

5. Назовите преимущества использования Class-Based Header Compression

Class-based header compression allows you to compress (and then decompress) a subset of the packets on your network. Class-based header compression acts as a filter; it allows you to specify at a much finer level the packets that you want to compress. For example, instead of compressing all RTP (or TCP) packets that traverse your network, you can configure RTP header compression to compress only those packets that meet certain criteria (for example, protocol type «ip» in a class called «voice).»

6. Для чего используется Voice Adaptive Traffic Shaping?

Voice Adaptive Traffic Shaping is only acailable with MQC-based Frame-Relay traffic shaping, and only with LLQ enabled in sharper-queue. The goal of VATS is to throttle the PVC’s sending rate once the system detected voice packets in the priority queue. The VATS feature is useful in the oversubscription scenaiio, where the customer sends traffic over the CIR. When the voice packet comes in the priority queue. the system will signal the shaper to slow its rate down to ensure router will never drop or delay any voice packets.

7. Для чего используется Voice Adaptive Fragmentation?

Frame Relay voice-adaptive fragmentation enables a router to fragment large data packets whenever
packets (usually voice) are detected in the low latency queueing priority queue or H.323 call setup
signaling packets are present. When there are no packets in the priority queue for a configured period of
time and signaling packets are not present, fragmentation is stopped. Frame Relay voice-adaptive fragmentation can be used in conjunction with or independent of
voice-adaptive traffic shaping.
To use voice-adaptive fragmentation, you must also have end-to-end fragmentation configured in a map
class or on the interface.

CCIE за год. Цикл 7. Тема 38. Вопросы.

1. Для чего используется IP SLA?

IP SLAs allows Cisco customers to analyze IP service levels for IP applications and services, to increase productivity, to lower operational costs, and to reduce the frequency of network outages. IP SLAs uses active traffic monitoring—the generation of traffic in a continuous, reliable, and predictable manner—for measuring network performance. Using IP SLAs, service provider customers can measure and provide service level agreements, and enterprise customers can verify service levels, verify outsourced service level agreements, and understand network performance. IP SLAs can perform network assessments, verify quality of service (QoS), ease the deployment of new services, and assist administrators with network troubleshooting. IP SLAs can be accessed using the Cisco software commands or Simple Network Management Protocol (SNMP) through the Cisco Round-Trip Time Monitor (RTTMON) and syslog Management Information Bases (MIBs).

2. Какой порт при настройке IP SLA не должен быть заблокирован?

IP SLA responder Control port — UDP 1967

3. Назовите параметры интервала и расписания выполнения IP SLA по-умолчанию

frequency — default is 60 seconds
ip sla monitor schedule
life — default is 3600 seconds (1 hour)
ageout — default is 0 seconds (never ages out)

4. Для чего используется Enhanced Object Tracking

This feature provides a more complete alternative to the Hot Standby Routing Protocol (HSRP) tracking mechanism. which allows you to track the line-protocol state of an interface. If the line protocol state of an interface goes down, the HSRP priority of the interface is reduced and another HSRP device with a higher priority becomes active. Theenhanced object tracking feature separates the tracking mechanism from HSRP and creates a separate, standalone tracking process that can be used by processes other than HSRP. This allows tracking other objects in addition to the interface line-protocol state. Aclient process, such as HSRP, can register an interest in tracking objects and request notification when the tracked object changes state.This feature increases the availability and speed of recovery of a routing system and decreases outages and outage duration.

5. Каким образом можно комбинировать несколько треков в Enhanced Object Tracking?

track <number> list boolean <and | or>

and —Specify that the list is up if all objects are up or down if one or more objects are down.
or —Specify that the list is up if one object is up or down if all objects are down.

CCIE за год. Цикл 7. Тема 37. Вопросы.

1. У вас на коммутаторе настроено 30 транков и через каждый из них проходит трафик 60 вланов. Сколько stp инстансов будет работать на коммутаторе?

Если VLANs одинаковые на транках то будет 60 STP instance. (кол-во VLAN = кол-во STP instance)
Если VLANs разные, то количество STP Instance зависит от платформы коммутатора:
2960 — 64 STP instance
3560, 3750 — 128 STP instance

2. Приведи примеры неудобства использования STP

При большом количестве VLAN, будет большое количество STP instance(что загружает коммутатор), но в реальности будет огриниченное количество физических топологий STP

3. Назовите ключевое отличие MST от STP

Уменьшение количества STP instance

4. Как ведет себя MSTP на access портах?

MSTP runs on these ports and have logical topologies either blocking or forwarding on the ports. Depending on VLANs to MSTI mapping, a given VLAN could be blocked on the access ports due to MSTP decision – even though the access VLANs are different, they use the same STP. To avoid this problem, do not run MSTP on accessports and use them for connecting “stub” devices only e.g. hosts and leaf switches.

5. Какие условия должны выполняться для того, чтобы кадр мог быть отправлен через порт?

?

6. Какие значения должны совпадать, для того, чтобы коммутаторы были в одном регионе?

— name of the region
— revision number
— MST VLAN-to-instance assignment map

7. Что использует MST для доставки информации о коммутаторах и как это работает?

The IST is the only spanning-tree instance that sends and receives BPDUs. All of the other spanning-tree instance information is contained in M-records, which are encapsulated within MSTP BPDUs. Because the MSTP BPDU carries information for all instances, the number of BPDUs that need to be processed to support multiple spanning-tree instances is significantly reduced.
All MST instances within the same region share the same protocol timers, but each MST instance has its own topology parameters, such as root switch ID, root path cost, and so forth. By default, all VLANs are assigned to the IST.

8. Дайте описание CIST Root и CIST Regional Root?

CIST Root is the bridge that has the lowest Bridge ID among ALL regions. This could be a bridge inside a region or a boundary switch in a region.

CIST Regional Root is a boundary switch elected for every region based on the shortest external path cost to reach the CIST Root. Path cost is calculated based on costs of the links connecting the regions, excluding the internal regional paths. CIST Regional Root becomes the root of the IST for the given region as well.

9. Опишите процесс выбора CIST Root.

— When a switch boots up, it declares itself as CIST Root and CIST Regional Root and announces this fact in outgoing BPDUs. The switch will adjust its decision upon reception of better information and continue advertising the best known CIST Root and CIST Regional Root on all internal ports. On the boundary ports, the switch advertises only the CIST Root Bridge ID and CIST External Root Path Cost thus hiding the details of the regions internal topology.
— CIST External Root Path Cost is the cost to reach the CIST Root across the links connecting the boundary ports i.e. the interregion links. When a BPDU is received on an internal port, this cost is not changed. When a BPDU is received on a boundary port, this cost is adjusted based on the receiving boundary port cost. In result, the CIST External Root Path Cost is propagated unmodified inside any region.
— Only a boundary switch could be elected as the CIST Regional Root, and this is the switch with the lowest cost to reach the CIST Root. If a boundary switch hears better CIST External Root Path cost received on its internal link, it will relinquish its role of CIST Regional Root and start announcing the new metric out of its boundary ports.
— Every boundary switch needs to properly block its boundary ports. If the switch is a CIST Regional Root, it elects one of the boundary ports as the CIST Root port and blocks all other boundary ports. If a boundary switch is not the CIST Regional Root, it will mark the boundary ports as CIST Designated or Alternate. The boundary port on a non regionalroot bridge becomes designated only if it has superior information for the CIST Root: better External Root Path cost or if the costs are equal better CIST Regional Root Bridge ID. This follows the normal rules of STP process.
— As a result of CIST construction, every region will have one switch having single port unblocked in the direction of the CIST Root. This switch is the CIST Regional Root. All boundary switches will advertise the regions CIST Regional Root Bridge ID out of their nonblocking boundary ports. From the outside perspective, the whole region will look like a single virtual bridge with the Bridge ID = CIST Regional Root ID and single root port elected on the CIST Regional Root switch.
— The region that contains the CIST Root will have all boundary ports unblocked and marked as CIST designated ports. Effectively the region would look like a virtual root bridge with the Bridge ID equal to CIST Root and all ports being designated. Notice that the region with CIST Root has CIST Regional Root equal to CIST Root as they share the same lowest bridge priority value across all regions.

10. Для чего используется параметр diametr в разрезе MST ?

Use the diameter keyword, which is available only for MST instance 0, to specify the Layer 2 network diameter (that is, the maximum number of switch hops between any two end stations in the Layer 2 network). When you specify the network diameter, the switch automatically sets an optimal hello time, forward-delay time, and maximum-age time for a network of that diameter, which can significantly reduce the convergence time. You can use the hello keyword to override the automatically calculated hello time.

11. Каким образом изменение топологии в CST влияет на другие регионы? Дайте полное объяснение.

Every MSTP region builds IST instance using the internal path costs and following the optimal internal topology, using the CIST Regional Root as the IST Root. The changes to CST may affect the IST in every region, as those changes may result in reelecting of the new CIST Regional Roots. Changes to the regions internal topologies normally do not affect the CST, unless those changes partition the region.