Route Optimization Master Network engineer should master the 50 router knowledge points

1. When to use multi-routing protocol?

When two different routing protocols are exchanged for routing information, it is necessary to use the multi-routing protocol. Routing redistribution can, of course, also exchange routing information. You do not need to use multiple routing protocols for the following situations:

Upgrade from the old version of the Internal Gateway Protocol (Interior Gateway Protocol,i G P) to the new version of I G P.

You want to use a different routing protocol but you must keep the original protocol.

You want to terminate the internal route in order to avoid interference from other routers that do not have strict filtering oversight capabilities.

You are in an environment of routers that are made up of multiple manufacturers.

2, what is the distance vector routing protocol?

The distance vector routing protocol is designed for small network environments. In a large network environment, such protocols in learning to route and maintain routing will produce a large amount of traffic, consuming too much bandwidth. If you do not receive a routing table update from an adjacent site within 9 0 seconds, it does not consider the neighboring site unreachable. Every 30 seconds, the distance vector routing protocol will send the entire routing table to the neighboring site, so that the routing table of the neighboring site is updated. In this way, it can collect a list of networks from other sites (directly connected or otherwise) to make routing choices. The distance vector routing protocol uses the hop count as a measure to calculate the number of routers to pass to the destination.

For example, the R I p uses the B e l l m a n-f o R D algorithm to determine the shortest path, i.e. the route to the destination as long as the minimum number of hops is reached. The maximum allowable hop count is typically 1 5. Terminals that must pass over 1 5 routers are considered unreachable.

The distance vector routing protocol has the following types: IP rip, IPX rip, A p p l e talk RT M p and I G R p.

3. What is link state routing protocol?

The link state routing protocol is more suitable for large networks, but because of its complexity, the router needs more C P u resources. It can discover broken links or newly connected routers in a shorter time, making the convergence time of the protocol shorter than the distance vector routing protocol. Normally, the H-E L lo Message in the adjacent station is not received within 1 0 seconds, and it is assumed that the neighboring station is unreachable. A link state router sends an update message to its neighbor to notify all of the links it knows. It determines that the measure of the optimal path is a numerical cost that is generally determined by the bandwidth of the link. The link with the least cost is considered to be optimal. In the shortest Path first algorithm, the value of the maximum possible cost can be almost unlimited.

If there is no change in the network, the router simply refreshes the routing table without the update periodically (the period can be from 3 0 minutes to 2 hours).

Link state routing protocols are available in the following ways: IP OSPF, IPX nlsp, and I s-i S.

Can a router use both the distance vector routing protocol and the link state routing protocol?

OK. Each interface can be configured to use a different routing protocol, but they must be able to exchange routing information by redistributing routes.

4. What is an Access table?

The Access table is the rule that the manager joins in a series of control packets input and output in the router. It is not generated by the router itself. Access tables allow or prohibit packets from entering or exporting to a destination. The table entries that access the table are executed sequentially, that is, when the packet arrives, it first depends on whether it is constrained by the first table entry, if not, and then executed downward, and if it matches the first table entry, whether it is allowed or forbidden, no more checking of the following table items is required.

Each protocol for each interface can have only one access table.

5. What types of Access tables are supported?

An Access table can be determined by its number. The specific protocols and their corresponding Access table numbers are as follows:

I p standard Access table number: 1~9 9

I p Extended Access table number: 1 0 0~1 9 9

I P x standard Access table number: 8 0 0~8 9 9

I P x Extended Access table number: 1 0 0 0~1 0 9 9

Appleta L k Access table number: 6 0 0~6 9 9

Tip in Cisco IOS Release11.2 or later, you can use a well-known access table to determine the access table numbered in 1~199.

6. How to create an IP standard Access table?

The creation of an I-P standard Access table can be done by the following command: Access-list access Listnumber {permit | deny} source [Source-mask]

In this command:

Access list Number: Determines which Access table this portal belongs to. It is a number from 1 to 9 9.

Permit | Deny: Indicates whether this entry allows or blocks information traffic from a specific address.

Source: Determines the Origin I P address.

S o u r c e-m a s K: determines which bits in the address are used for matching. If a bit is "1", it indicates that the bit in the address is not in the tube, and if it is "0", it indicates that the bit in the address will be used for matching. Wildcard characters can be used.

The following is an example of an Access table in a router configuration file:

router# Show Access-lists

Standard IP access list 1

Deny 204.59.144.0, wildcard bits 0.0.0.255

Ermit any

7. When to use route redistribution?

Routing redistribution is typically configured on routers that are responsible for learning the route from an autonomous system and then broadcasting to another autonomous system. If you are using the I g r p or e i g r p, routing redistribution is usually performed automatically.

8, what is the management distance?

Administrative distance refers to the routing confidence of a routing protocol. Each routing protocol is based on reliability from high to low, assigning a trust level in turn, which is called the administrative distance. For routing information between two different routing protocols to a destination, the router first determines which protocol to trust based on the administrative distance.

9, how to configure the redistribution?

Before you proceed with routing redistribution, you must first:

1) Decide where to add the new protocol.

2) determine the autonomous system border router (ASBR).

3) Decide which agreement at the core, which at the border.

4) Determine the direction of routing redistribution.

The following command can be used to redistribute routing updates (this example is for OSPF):

Router (config-router) #redistribute Protocol[process-id] [metric metric-value] [metric-type type-value] [subnets]

In this command:

Protocol: Indicates the source routing protocol to which the router will route the redistribution.

The main values are: BGP, EQP, IGRP, ISIS, OSPF, static [IP], connected, and RIP.

Process-id: Indicates the process ID of the OSPF.

Metric: is an optional parameter used to indicate the measure of the redistributed route. The default measure value is 0.

10. Why is it important to identify adjacent routers?

Identifying adjacent routers in a small network is not a major problem. Because when a router fails, other routers can converge within an acceptable time. However, in a large network, it is possible to find a faulty router with a large delay. Knowing that an adjacent router can accelerate convergence is because the router knows the faulty router more quickly because the interval of the Hello message is shorter than the interval between routers exchanging information.

Routers that use the distance vector routing protocol will not be able to find adjacent routers when they do not send routing updates on adjacent routers, which typically takes 10-90 seconds. Routers that use the link state routing protocol do not receive a Hello message to find an adjacent router unreachable, which typically takes 10 seconds.

11, Distance vector routing protocol and link state routing protocol How to find an adjacent router?

Routers that use the distance vector routing protocol to create a routing table that includes a network that is directly connected to it, and it sends the routing table to a router that is directly connected to it. The adjacent router merges the received routing table into its own routing table, and it also sends its own routing table to its adjacent router. Routers that use the link state routing protocol to create a link state table, including a list of the entire network destination station. In the update message, each router sends its entire list. When the neighboring router receives the update message, it copies the contents and sends the information to its neighbor station. There is no need to recalculate the routing table content when it is forwarded.

Note that routers using IGRP and EIGRP broadcast Hello messages to discover neighboring stations while exchanging routing update information like OSPF. EIGRP holds a neighbor table for each network layer protocol, which includes the address of the neighboring station, the number of messages waiting to be sent in the queue, the average time it takes to receive from the neighbor or the message to the neighbor, and the time that no messages are received from the neighbor before the link is determined to be disconnected.

12. What is an autonomous system?

An autonomous system is a router and network group that is under the control of a management authority. It can be a router directly connected to a LAN, but also connected to the Internet; it can be a network of multiple LANs interconnected by an enterprise backbone. All routers in an autonomous system must connect to each other, run the same routing protocol, and assign the same autonomous system number. The links between autonomous systems use external routing protocols, such as B G P.

13. What is BGP?

BGP (Border gatewayprotocol) is a routing protocol that dynamically switches routing information between autonomous systems. The classic definition of an autonomous system is a set of routers under the control of an administrative agency that uses IGP and ordinary metrics to forward messages to other autonomous systems.

The term autonomous system is used in BGP to emphasize the fact that the administration of an autonomous system provides a unified internal routing plan for other autonomous systems, which provides a consistent description for those networks that are reachable through it.

14. What types of sessions does BGP support?

The session between BGP neighboring routers is built on top of the TCP protocol. The TCP protocol provides a reliable transport mechanism that supports two types of sessions:

o external BGP (EBGP): is a session between routers that belong to two different autonomous systems. These routers are adjacent, sharing the same media and subnets.

o Internal BGP (IBGP): is a session between routers within an autonomous system. It is used to coordinate and synchronize the process of finding routes within autonomous systems. BGP routers can be located anywhere in the autonomous system, or even in the middle of a number of routers.

Note the content of the initial data stream is the entire BGP routing table. However, when the routing table changes later, the router only transmits the changed portions. BGP does not need to periodically update the entire routing table. Therefore, during the connection has been established, a BGP sender must save the entire BGP routing table that is common to all current sibling routers. The BGP router periodically sends keep alive messages to confirm that the connection is active. When an error or special situation occurs, the router sends a notification message. When an error occurs on a connection, a notification message is generated and the connection is disconnected. "-From RFC11654, BGP operations.

15. Does BGP allow routing redistribution?

Allow. Because BGP is primarily used for routing between autonomous systems, it must support the synthesis of routing tables for RIP, OSPF, and IGRP in order to transfer their routing tables to an autonomous system. BGP is an external routing protocol, so its operation differs from an internal routing protocol. In BGP, you can use the Network command to create a route in the BGP routing table only if a route already exists in the IP routing table.

16. How do I display all BGP routes in the database?

To display all BGP routes in the database, simply enter under the EXEC command line:

How IP BGP paths

The output of this command may be:

Address Hash ref** Metricpath

0 x 2 9 7 A 9 C 0 2 0 I

17. What is horizontal segmentation?

Horizontal segmentation is a technique that avoids the advent of routing loops and accelerates routing convergence. Because the router may receive routing information it sends itself, and this information is useless, the horizontal segmentation technique does not reverse-advertise any routing updates received from the terminal, and only advertises those routes that are not purged by counting to infinity.

18. How is the routing ring generated?

Because of the network routing aggregation time, the routing table in the new route or changed routes can not be quickly in the whole network stability, so that there are inconsistent routes exist, resulting in a routing ring.

19, what is the measure value?

measures represent distances. They are used to determine the optimal route when searching for a route. Each routing algorithm generates a numeric value (measure) for each path through the network when the routing table is generated, and the minimum value represents the optimal path. The calculation of a measure can take only one attribute of the path, but more complex measures are produced by synthesizing multiple attributes of the path. Some of the commonly used metrics are:

Number of hops: The number of router output ports to pass through the message.

Ticks: Latency of the data link (approximately 1/18 per second).

Price: Can be an arbitrary value, based on bandwidth, cost, or other network manager-defined calculation methods.

Bandwidth: The capacity of the data link.

Delay: The length of time the message is transmitted from the source to the destination.

Load: The size of a network resource or part of a link that has been used.

Reliability: The ratio of error bits to the network link.

Maximum Transmission Unit (MTU): The maximum message length (in bytes) that can be accepted for all links on a path.

What type of route metrics does IGRP use? What is this metric made of?

IGRP uses multiple route metrics. It includes the following sections:

Bandwidth: The minimum bandwidth value between source-to-destination.

Delay: The accumulated interface delay in the path.

Reliability: The worst possible reliability between source to destination, based on the state of the link hold.

Load: The load of the source-to-destination link in the worst case, expressed in bits per second.

MTU: the smallest m T u value in the path.

20. Can the measures be modified or adjusted?

Plus a positive offset. The complete structure of this command is as follows: You can use the offset-list router subcommand

Adds a positive offset to the network input and output measures in the Access table.

offset-list {in|out} offset [access-list] nooffset-list {in|out} offset [access-list]

If the value of the parameter list is 0, then the offset parameter is added to all measures. If the value of offset is 0, then it has no effect. For IGRP, the value of the offset is only added to the time delay. This subcommand also applies to rip and Hello routing protocols.

This offset can be cleared using the No offset-list command with the appropriate parameters.

In the following example, a router using IGRP adds an offset to the latency of all output measures 10:offset-list out 10

The following is an example of adding the same offset to the Access table 121:

Offset-list out 10 121

21. What are the five pieces of information each router needs to know when looking for a route?

All routers need the following information to find the route for the message:

Destination Address: The destination host for message delivery.

Determination of the neighboring station: indicates who is directly connected to the router's interface.

Discovery of Routes: discover which networks the neighboring station knows.

Select route: Provides the best (related to the measure) path to the destination by learning from the neighboring station.

Maintain routing information: The router holds a routing table that stores all the routing information that is known.

22. Are the routing protocols supported by Cisco routers compatible with the protocols of other manufacturers ' devices?

All routing protocols supported by IGRP and EIGRP,CISCO routers are compatible with the same protocols implemented by other manufacturers. IGRP and EIGRP are the patented products of Cisco.

23. What does the information about the table entries in the RIP routing table indicate?

Each table entry in the RIP routing table provides a certain amount of information, including the final destination address, the next hop address to the destination, and a measure. This measure represents the distance to the destination terminal (number of hops). Other information can also be included.

24. Does the CISCO3600 series routers currently support WAN interface cards wic-2t and wic-2a/s?

The CISCO3600 series routers support both the WIC-2T and wic-2a/s WAN interface cards in versions 12.007XK and later.

However, it is important to note that:

Only the Fast Ethernet hybrid Network module can support both of these WAN interface cards.

The network modules that support both of these interface cards are as follows:

nm-1fe2w, nm-2fe2w, nm-1fe1r2w, nm-2w.

The Ethernet hybrid network module is not supported, as follows:

nm-1e2w,nm-2e2w, nm1e1r2w.

25. CISCO3600 Series Router NM (4A/S,NM (8A/S network module and WIC (2a/s WAN interface card is the maximum sync rate supported?

These network modules and WAN interface cards are capable of both asynchronous and synchronous support. The maximum supported asynchronous rate is 115.2Kbps and the maximum synchronization rate is 128Kbps.

26, WIC-2T and wic-1t cable each is what kind?

Wic-1t:db60 to V35 or RS232, 449 and other cables. such as: CAB-V35-MT.

Wic-2t:smart type V35 or RS232, 449 and other cables. such as: CAB-SS-V35-MT.

27. What is the difference between the MCE1 on the Cisco 7000 series and the E1, CE1 on the Cisco 2600/3600?

The MCE1 on the Cisco 7000 can be configured as E1, CE1, while the E1, CE1 on the Cisco 2600/3600 only supports its own functionality.

28. Does the CISCO 2600 series routers support inter-VLAN routing, and what are the requirements for iOS software?

In Cisco (2600 series routers, only Cisco2620 and Cisco2621 can support inter-VLAN routing (The Hundred-Gigabit eloquence supports inter-VLAN routing). And if the inter-VLAN routing is supported, the iOS software must include the IP Plus feature set.

29. What are the different hardware Cisco3660 routers compared to 3620/3640 routers?

The different points are as follows: www.luyouqiwang.com

* The basic configuration of the Cisco3660 router includes 1 or 2 10/100m Adaptive Fast Ethernet interfaces, while the cisco3620/3640 basic configuration does not include an Ethernet interface.

* The Cisco3660 router supports hot-swapping of network modules, while cisco3620/3640 does not support hot-swapping of network modules.

* The redundant power supply of the Cisco3660 is built-in, while the cisco3620/3640 redundant power supply is external.

30, why 3640 does not recognize nm-1fe2w?

Need to upgrade iOS to 12.0.7T

About switch Issues:

31. How is the stack of Catalyst 35500XL/2950XL implemented?

A. A dedicated stacking cable is required, 1 m long or 50 cm long (cab-gs-1m or cab-gs-50cm) and a dedicated gigabit stacking card Gigastack GBIC (WS-X3550-XL) with cab-gs-50cm stacking cable.

. There are 2 stacking methods available: daisy-chaining (with 1G bandwidth) or point-to-point (2G bandwidth available).

C. There are 2 ways to do backups.

D. Daisy chaining can support up to 9 switch stacks, and point-to-point method can support up to 8 units.

32. When the Catalyst 3550 XL series switch does stack, does it support redundant backup?

The CATALYST3550XL series switches are stacked in two ways: daisy-chaining and point-to-dot.

When the daisy-chain mode, the stack of switches connected in turn, the switch can reach 1Gbps transmission bandwidth;

A separate CATALYST3508G-XL switch is required when using the point-to-dot approach

The rest of the switches are connected to the 3508G by stacking the GBIC cards and stacking cables, which can reach a maximum of 2Gbps full-duplex transmission bandwidth.

Both of these methods support redundant connections on the stack, respectively. When Daisy chaining is used, redundant connections are done by connecting the top switch to the bottom switch with a stacked cable. When using a point-to-point connection, it is done by using the 2nd 3508 switch.

33, Catalyst3550 XL of a gigabit port using a stack card stack, the other gigabit port can be connected to the gigabit switch or gigabit server?

OK. Use of the 1000base-sx gbic or 1000BASE-LX/LH gbic is required.

34, Ethernet Channel Tech. What network devices can be applied between? How to use?

can be applied between switches, between switches and routers, between switches and servers

You can use Ethernet Channel Tech for 2 or 4 10/100mbps or 1000Mbps ports, up to 400M (10/100mbps ports), 4G (1000Mbps ports), or 800M (10/100mbps ports), Bandwidth of 8G (1000Mbps port).

35. What is the role of Ethernet Channel technology?

Increased bandwidth, load balancing, line Backup

36, when the port is set to Ethernet channel, how to select the line?

Depending on the Ethernet source address and destination address of the data frame, the last 1 bits or 2 bits are done or operated to determine which link to output from. The router is based on the network address to do or operate, to determine the output of the link.

37. What is the difference between Ethernet Channel technology and PAgP (Port Aggregation Protocol)?

PAGP is an enhanced version of the Ethernet channel, which supports Spanning tree protocol and uplink Fast on the Ethernet channel, and supports automatic configuration of Ethernet channel bundles.

Minimum required number of power supplies 1 2

Packet forwarding rate 18Mpps 18Mpps

Back panel bandwidth 24Gbps 60Gbps

38. Does the Catalyst4000 series support ISL?

Supported starting from Supervisor Engine Software Release 5.1.

31. What is the difference between redundant power Options 4008/2 and 4008/3 for Catalyst4000 switches?

There are two power slots on the Catalyst4003 switch chassis, which comes with a power supply at the factory, and 4008/2 is a redundant power supply specifically tailored to it. The Catalyst4006 has three power slots on the chassis, with 2 power supply at the factory, and 4008/3 as a dedicated redundant power supply for its customization.

39. Does the Catalyst 4006 three-layer switching module contain no Ethernet ports?

No, the Catalyst4006 three-layer switching module contains 32 10/100 adaptive ports and 2 gigabit ports. When used on 4003, it can replace the original WS-X4232-GB-RJ module without affecting the network structure.

40. When the Catalyst 4000 series Modular switch uses the Gigabit switching module, how to choose the existing two switching modules (product number below)?

WS-X4306-GB Catalyst 4000 Gigabit Ethernet module,6-ports (GBIC)

WS-X4418-GB Catalyst 4000 GE Module, Server switching18-ports (GBIC)

These two modules are used in different environments

The WS-X4306-GB is a 6-port Gigabit Switch module, each port exclusive gigabit bandwidth, suitable for the backbone of the network, used to connect the switch with Gigabit interface, can also be connected to a server with Gigabit network card.

The WS-X4418-GB is a 18-port Gigabit switching module with two ports that are exclusive gigabit bandwidth, while the other 16 port shares 8G full-duplex bandwidth, but each port can burst to gigabit. This module is suitable for connecting gigabit servers where the server is relatively centralized, rather than connecting to the network backbone.

41. What are the backplane bandwidth and packet forwarding rates for the Catalyst 6000 series?

The backplane bandwidth of the Catalyst 6500 series can be extended to 256Gbps, and the packet forwarding rate can be extended to 150Mpps; The Catalyst 6000 series provides a cost-effective solution to 32Gbps backplane bandwidth and a 15MPPS packet forwarding rate.

42. How many M DRAM does the MSFC of the Catalyst 6000 series require?

The Catalyst 6000 series iOS software is housed in MSFC, and MSFC requires 128M DRAM. The default configuration already contains 128M DRAM.

43. Is there a limit on the slots on the Catalyst 6000 series?

In addition to the first slot dedicated to the engine, the second slot can be used for the backup engine or line card, and the other slots are used for line cards.

44. How many engines are there in the Catalyst 6000 series?

The engines of the Catalyst 6000 series are divided into Supervisor Engine 1 and Supervisor Engine 1 a two, of which Supervisor engine 1 A has two specific backup engines. The models are as follows: Model description

Ws-x6k-sup1-2ge Catalyst 6000 Supervisor Engine1 engine with two gigabit ports (gbic required)

Ws-x6k-sup1a-2ge Catalyst 6000 Supervisor engine1a engine Enhanced QoS features with two gigabit ports (gbic required)

WS-X6K-SUP1A-PFC Catalyst 6000 Supervisor engine1a engine with two gigabit ports (gbic required) and PFC cards

WS-X6K-S1A-PFC/2 Catalyst 6000 Supervisor engine1a redundancy engine with two gigabit ports (gbic required) and PFC cards

WS-X6K-SUP1A-MSFC Catalyst 6000 Supervisor engine1a engine with two gigabit ports (gbic required) and MSFC, PFC cards

WS-X6K-S1A-MSFC/2 Catalyst 6000 Supervisor engine1a redundant engine with two gigabit ports (gbic required) and MSFC, PFC cards

45. Does the backup engine on the Catalyst 6000 series have to be consistent with the main engine?

Yes. The backup engine of the Catalyst 6000 series must be consistent with the main engine, for example, the engine without the msfc& PFC should not be backed up with a msfc& PFC engine. In addition, WS-X6K-SUP1A-PFC and WS-X6K-SUP1A-MSFC have dedicated backup engines.

The correspondence between the master and the standby engine is as follows:

Main Engine Backup engine

Ws-x6k-sup1-2ge Ws-x6k-sup1-2ge

Ws-x6k-sup1a-2ge Ws-x6k-sup1a-2ge

WS-X6K-SUP1A-PFC WS-X6K-S1A-PFC/2

WS-X6K-SUP1A-MSFC WS-X6K-S1A-MSFC/2

46. What are the routing protocols supported by the CATALYST 6000 series?

The routing protocols supported by the CATALYST 6000 series are: OSPF, IGRP, EIGRP, BGP4, Is-is, rip and rip II;

For multicast PIM support sparse and dense two modes;

Supported non-IP routing protocols are: NLSP, IPX RIP/SAP, IPX EIGRP, RTMP, Apple talk EIGRP, and DECnet Phase IV and V.

47. What are the network protocols supported by the CATALYST 6000 series? If the engine is sup-1a-2ge, how to realize the function of three layer Exchange?

6Mpps IP, IP multicast, and IPX are supported on MSM. The MSFC on the engine supports 15MPPS IP, IP multicast, IPX, and AppleTalk, Vines, DECnet.

Implemented with MSM. On 6000, only the engine containing MSFC can achieve three-layer switching via MSFC, and on 6000, MSFC cannot be ordered separately.

48, Catalyst? 6000 switches and catalyst? What is the difference between a 6500 switch? 6000 can the switch be upgraded to a 6500 switch?

Catalyst? The backplane bandwidth of the 6000 series switches is 32G, while the backplane bandwidth of the 6500 series switches can be extended to 256G maximum. Since the two series switches use a different backplane bus structure, the 6000 switch cannot be upgraded to a 6500 series switch.

However, these two series switches use the same switching module.

49, catalyst3508g can also use the same daisy-chain stacking mode as Catalyst3524?

It's perfectly possible.

50. When configuring uplink-fast between switches, do I need to turn off the original Spanning-tree option? No, Uplink-fast is actually using a simplified spanning-tree algorithm that is compatible with the standard Spanning-tree, so you do not need to turn this feature off.