The 44 key points for network engineers to master: Linux Enterprise Application-Linux server application information. The following is a detailed description.
1. When to use the multi-route protocol?
When two different routing protocols need to exchange routing information, they need to use multiple routing protocols. Of course, route redistribution can also exchange route information. Multi-route protocol is not required in the following cases:
Upgrade the old version of the Internal Gateway Protocol (Interior Gateway Protocol, I g p) to the new version of the I G P.
To use another routing protocol, you must retain the original one.
You want to terminate the internal route to avoid interference from other routers that do not strictly filter the monitoring function.
You are in an environment composed of routers from multiple manufacturers.
What is distance vector routing protocol?
The distance vector routing protocol is designed for small network environments. In a large network environment, such protocols will generate large traffic when learning routes and maintaining routes, occupying excessive bandwidth. If the route selection table update is not received from the adjacent site within 9 0 seconds, the adjacent site is considered inaccessible. Every 30 seconds, the distance vector routing protocol sends the entire route selection table to the adjacent site to update the route selection table of the adjacent site. In this way, it can collect a list of networks from other sites (directly connected or connected in other ways) for route selection. Distance Vector Routing uses the number of hops as the metric value to calculate the number of routers that need to pass to the destination.
For example, r I p uses the B e l m a n-F o r d algorithm to determine the shortest path, that is, the line that can reach the destination as long as it passes through the smallest hop count. The maximum number of hops allowed is usually set to 1 5. Terminals that must pass through more than five vrouters are considered inaccessible.
Distance Vector routing protocols include ip rip, ipx rip, A p l e Talk rt m p, And I G R P.
What is the link status routing protocol?
The link status routing protocol is more suitable for large networks. However, due to its complexity, the router needs more c p u resources. It can detect broken links or new routers in a shorter period of time, so that the convergence time of the Protocol is shorter than that of the Distance Vector routing protocol. Generally, if you do not receive the he l lo packet from the neighboring station within one 0 second, it is deemed that the neighboring station is no longer reachable. A connection status router sends an update message to its neighbor to notify it of all the links it knows. It determines that the measurement value of the optimal path is a numerical cost, which is generally determined by the bandwidth of the link. Links with the minimum cost are considered optimal. In the Shortest Path priority algorithm, the maximum possible cost is almost unlimited.
If the network does not change, the router only needs to periodically refresh the route selection table that has not been updated (the duration of the cycle can be from 3 0 minutes to 2 hours ).
The connection status routing protocols include ip ospf, ipx nlsp, And I s-I S.
Can a vro use the distance vector routing protocol and the link status routing protocol?
Yes. Each interface can be configured to use different routing protocols. However, they must be able to exchange routing information by allocating routes. (Route redistribution will be discussed later in this chapter .)
2. What is an access table?
The access table is a series of rules that the manager adds to control data packets input and output in the vro. It is not generated by the router itself. The Access Table allows or disables data packets from entering or outputting to the destination. The table items for accessing the table are executed sequentially. When the data packet arrives, the system first checks whether it is restricted by the first table item. If not, it is executed sequentially; if it matches the first table item, you do not have to perform the following table item check whether it is allowed or disabled.
Each Protocol of each interface can have only one access table.
What types of access tables are supported?
The number of an access table can be determined. The specific protocol and its corresponding access table number are as follows:
◎ I P standard Access Table No.: 1 ~ 9 9
◎ I P extended access table No.: 1 0 0 ~ 1 9 9
◎ I P X standard Access Table No.: 8 0 0 ~ 8 9 9
◎ I P X extended access table No.: 1 0 0 0 ~ 1 0 9 9
◎ AppleTa l k Access Table No.: 6 0 0 ~ 6 9 9
Note: In Cisco IOS Release11.2 or later versions, you can use the famous access table to determine the number between 1 and later ~ 199 access table.
How do I create an IP standard access table?
The following command creates an I P standard Access table: access-list Access list number {permit | deny} source [source-mask]
In this command:
◎ Access list number: determines which access table the entry belongs. It is a number ranging from 1 to 9.
◎ Permit | deny: indicates whether the entry permits or blocks information traffic from a specific address.
◎ Source: determine the source 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 unnecessary. 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 the vro configuration file:
Router # show access-lists
Standard IP access list 1
Deny 204.59.144.0, wildcard bits 0.0.0.255
Ermit any
3. When will route redistribution be used?
Route redistribution is usually configured on routers responsible for learning routes from one autonomous system and then broadcasting to another autonomous system. If you are using I g r p or e I G R P, route redistribution is generally automatically executed.
4. What is Management Distance?
Management Distance refers to the route reliability of a routing protocol. Each routing protocol allocates a level of trust from high to low Based on the availability. This level of trust is called the Management Distance. For the routing information from two different routing protocols to one destination, the router first determines which Protocol to trust based on the Management Distance.
5. How to configure redistribution?
Before route redistribution, you must first:
1) decide where to add a new protocol.
2) determine the border router (ASBR) of the autonomous system ).
3) decide which protocol is at the core and which is at the boundary.
4) determines the route redistribution direction.
You can use the following command to reallocate route updates (this example is for OSPF ):
◎ Protocol: Specifies the source route protocol for Route redistribution on the vro.
The main values are bgp, eqp, igrp, isis, ospf, static [ip], connected, and rip.
◎ Process-id: indicates the OSPF process ID.
◎ Metric: it is an optional parameter used to specify the metric value of the redistribution route. The default measurement value is 0.
6. Why is it important to determine the adjacent router?
Determining the adjacent router in a small network is not a major problem. When a router fails, other routers can converge within an acceptable period of time. However, in a large network, the latency of a faulty router may be high. Knowing that the adjacent router can accelerate convergence, because the router can know the faulty router more quickly, because the interval of hello messages is shorter than the interval of router information exchange.
When a router using the distance vector routing protocol does not send route update information to the adjacent router, it can be found that the adjacent router is no longer reachable. This time is generally 10 ~ 90 seconds. The router that uses the link status routing protocol does not receive the hello message, it can be found that the adjacent router is not reachable, this interval is generally 10 seconds.
How can I find the adjacent router through distance vector routing protocol and link status routing protocol?
A Router using the Distance Vector Routing Protocol creates a route table (including the network directly connected to it), and sends the route table to the router directly connected to it. The adjacent router combines the received route table into its own route table, and also sends its route table to its adjacent router. A connection status table is created for the router that uses the link status routing protocol, including the list of the entire network destination site. In the UPDATE message, Each router sends its entire list. When the adjacent router receives the update packet, it copies the content and sends the information to its neighbor. It is not necessary to recalculate the content of the route table.
Note that the hello message is broadcast by the routers of IGRP and VPN to discover the adjacent station and exchange route update information like OSPF. For each network layer protocol, it includes the address of the neighboring station, the number of packets waiting to be sent in the queue, and the average time required to receive or send packets to the neighboring station, and the time when no message is received from the neighboring station before the link is confirmed to be disconnected.
7. What is an autonomous system?
An autonomous system is a vro and network group under the control of a management organization. It can be a vro that is directly connected to a LAN and connected to the Internet. It can be a LAN that is interconnected by an enterprise backbone network. All routers in an autonomous system must connect to each other, run the same routing protocol, and assign the same autonomous system number. Links between autonomous systems use external routing protocols, such as B G P.
8. What is BGP?
Border GatewayProtocol is a routing protocol that dynamically exchanges route information between autonomous systems. A classic definition of an autonomous system is a group of routers under the control of a management organization. It uses IGP and common measurement values to forward packets to other autonomous systems.
The term autonomous systems are used in BGP to emphasize the fact that the management of an autonomous system provides a unified internal routing plan for other autonomous systems, it provides a consistent description for networks that can be reached through it.
9. What session types does BGP support?
The session between BGP neighboring routers is based on the TCP protocol. The TCP protocol provides a * transmission mechanism that supports two types of sessions:
O external BGP (EBGP): refers to the session between routers belonging to two different Autonomous Systems. These routers are adjacent and share the same media and subnet.
O internal BGP (IBGP): refers to the session between routers in an autonomous system. It is used to coordinate and synchronize routing processes in autonomous systems. BGP routers can be separated by several routers at any location in the autonomous system.
Note: "The content of the initial data stream is the entire BGP Route table. However, when the route table changes later, the router only transmits the changed part. BGP does not need to update the entire route table periodically. Therefore, when a connection has been established, a BGP sender must save the entire BGP Route table that is currently common to all vrouters at the same level. The BGP router periodically sends the Keep Alive message to confirm that the connection is activated. When an error or special situation occurs, the router sends a Notification message. When a connection error occurs, a notification message is generated and the connection is disconnected. "-From rfc000054 and BGP.
10. Does BGP allow route redistribution?
Yes. Because BGP is mainly used to select routes between autonomous systems, it must support the synthesis of routes selection tables for RIP, OSPF, and IGRP, so that their route tables can be transferred to an autonomous system. BGP is an external routing protocol, so its * operation is different from an internal routing protocol. In BGP, only when a route already exists in the IP route table can you use the NETWORK command to create a route in the BGP Route table.
11. How do I display all BGP routes in the database?
To display all BGP routes in the database, enter the following command line in the EXEC command line:
How ip bgp paths
The output of this command may be:
Address Hash Refcount MetricPath
0x2 9 7 A 9 C 0 2 0 I
12. What is horizontal segmentation?
Horizontal segmentation is a technology that avoids the appearance of routing rings and accelerates route aggregation. Because the router may receive the route information sent by itself, and this information is useless, the horizontal segmentation technology does not reverse notice any route update information received from the terminal, instead, only route entries that are not cleared due to infinite counts are advertised.
13. How is a routing ring generated?
Due to the existence of the route aggregation time of the network, the new or changed route in the route table cannot be stable in the whole network quickly, so that there are inconsistent routes, so a routing ring will be generated.
14. What is a metric value?
The measurement value indicates the distance. They are used to determine the optimal route when looking for a route. When a route table is generated by each routing algorithm, a value (measurement value) is generated for each route through the network. The minimum value indicates the optimal path. The Calculation of measurement values can only consider one feature of the path, but more complex measurement values are generated by combining multiple features of the path. Some common metric values include:
◎ Number of hops: the number of router output ports to pass through.
◎ Ticks: latency of data links (about 1/18 per second ).
◎ Cost: it can be an arbitrary value, which is calculated based on bandwidth, fees, or other network manager-defined calculation methods.
◎ Bandwidth: the capacity of the data link.
◎ Latency: the length of time the message is sent from the source to the destination.
◎ Load: the size of the used part of the network resource or link.
◎ Availability *: Ratio of error bits on the network link.
◎ Maximum transmission unit (MTU): The maximum message length (in bytes) acceptable to all links in a path ).
What type of Route metric value does IGRP use? What is the composition of this metric value?
IGRP uses multiple route metric values. It includes the following parts:
◎ Bandwidth: The minimum bandwidth value between the source and destination.
◎ Latency: The interface latency accumulated in the path.
◎ Availability: The worst possible possibility between the source and destination, based on the state of link persistence.
◎ Load: the load of the link between the source and target in the worst case, expressed in bits per second.
◎ MTU: The minimum m t u value in the path.
15. Can the metric value be modified or adjusted?
Add a positive offset. The complete structure of this command is as follows: You can use the OFFSET-list router subcommand.
Add a positive offset for the network input and output metric values in the access table.
If the value of the parameter LIST is 0, the OFFSET parameter is added to all measurement values. If the value of OFFSET is 0, there is no effect. For IGRP, the offset value is only added to the latency. This sub-command also applies to the RIP and hello routing protocols.
Use the no offset-LIST command with the appropriate parameter to clear this OFFSET.
In the following example, a router using IGRP adds offset 10: offset-list out 10 to the latency of all output metric values.
Here is an example of adding the same offset to Access Table 121:
Offset-list out 10 121
16. What information does each router need to know when looking for a route?
All routers need the following information to find routes for packets:
◎ Destination Address: the destination host for sending packets.
Determine the neighboring station: specify who is directly connected to the router interface.
◎ Discovery of routes: Find the networks that the neighboring sites know.
◎ Route Selection: Provides the optimal route (related to the metric value) to reach the destination based on the information learned from the neighboring station.
◎ Keep route information: the router saves a route table, which stores all the route information it knows.
17. Are the routing protocols supported by Cisco routers compatible with those of other manufacturers' devices?
All routing protocols supported by Cisco routers are compatible with the same protocols implemented by other manufacturers, except for IGRP and VPN. IGRP and VPN are Cisco's patented products.
18. What are the descriptions of table items in the RIP route table?
Each table item in the RIP route table provides certain information, including the destination address, the next hop address to the destination, and the measurement value. This metric value indicates the distance to the target terminal (number of hops ). Other information can also be included.
Router question supplement:
1. Does Cisco3600 series routers currently Support WAN Interface Card WIC-2T and WIC-2A/S?
Cisco3600 series routers support both WIC-2T and WIC-2A/S wan interface cards in 12.007XK and later versions.
However, note the following:
Only the Fast Ethernet hybrid network module can support these two wan interface cards.
The network modules supporting these two interface cards are as follows:
NM-1FE2W, NM-2FE2W, NM-1FE1R2W, NM-2W.
The Ethernet hybrid network module does not support the following features:
NM-1E2W, NM-2E2W, NM1E1R2W.
19. What is the maximum rate of synchronization supported by Cisco3600 series routers (4A/S, NM (8A/S network module and WIC (2A/s wan Interface Card?
These network modules and WAN interface cards support both asynchronous and synchronous interfaces. The maximum asynchronous rate supported is 115.2 Kbps, and the maximum synchronous rate is 128 Kbps.
20, WIC-2T and WIC-1T cable each is what kind?
WIC-1TB60 to V35 or RS232, 449 and other cables. Such as: CAB-V35-MT.
WIC-2T: SMART type to V35 or RS232, 449 and other cables. Such as: CAB-SS-V35-MT.
21. What is the difference between MCE1 in the Cisco 7000 Series and E1 and CE1 in Cisco 2600/3600?
MCE1 on Cisco 7000 can be configured as E1 and CE1, while E1 and CE1 on Cisco 2600/3600 only support their own functions.
22. Does a Cisco 2600 series router support inter-VLAN routing? What are the requirements for IOS software?
In Cisco (2600 series routers, only Cisco2620 and Cisco2621 support inter-VLAN routing (MB ports support inter-VLAN Routing ). If Inter-VLAN routing is supported, IOS software must include the IP Plus feature set.
23. What are the differences in hardware between the Cisco3660 router and the 3620/3640 router?
The differences are as follows:
* The basic configuration of the Cisco3660 router includes one or two 10/100 M Adaptive Fast Ethernet interfaces. The basic configuration of Cisco3620/3640 does not include Ethernet interfaces.
* Cisco3660 vro supports hot swapping of network modules, while Cisco3620/3640 does not support hot swapping of network modules.
* The Cisco3660 redundant power supply is built in, while the Cisco3620/3640 redundant power supply is external.
24. Why 3640 cannot identify NM-1FE2W?
Upgrade IOS to 12.0.7T
Vswitch Problems
About vswitches:
1. How is the stacking of Catalyst 35500XL/2950XL implemented?
A. dedicated stacked cables, 1 m long or 50 cm long (CAB-GS-1M or CAB-GS- 50CM) and dedicated Gigabit stacked card GigaStack GBIC (WS-X3550-XL) (the card already contains CAB-GS- 50CM stacked cables) are required ).
You can use either the chrysanthemum Link Method (providing 1g bandwidth) or the point-to-point method (providing 2G bandwidth ).
C. Both methods can be used for backup.
D. The Chrysanthemum Link Method supports stacking of up to 9 switches, and the point-to-point method supports up to 8 switches.
2. is redundant backup supported when the Catalyst 3550 XL series switches are stacked?
There are two ways to stack the ipvst3550xl series switches: The Chrysanthemum link mode and the point-to-point mode.
When the chrysanthemum link is used, the stacked switches are connected in turn, and the transmission bandwidth between switches can reach 1 Gbps;
When using the point-to-point approach, a separate Catalyst3508G-XL switch is required,
Other switches are connected to GB by stacked GBIC cards and stacked cables, which can achieve a full duplex transmission bandwidth of up to 2 Gbps.
Both methods support stack redundancy. When you use the chrysanthemum link connection method, the redundant connection is completed by connecting the top switch with the bottom switch with a stacked cable. When a point-to-point connection is used, 2nd 3508 switches are used.
25. After a gigabit port of ipvst3550 XL is stacked with a stacked card, can another gigabit port connect to a gigabit switch or a gigabit server?
Yes. Use 1000Base-SX GBIC or 1000Base-LX/lh gbic.
26. Ethernet Channel Tech. What network devices can be used? How to use it?
It can be used between vswitches, between vswitches and vrouters, and between vswitches and servers.
Two or four 10/100 Mbps or Mbps ports can be used by Ethernet Channel Tech ., up to 400 M (10/100 Mbps port), 4G (800 Mbps port), 10/100 M (Mbps port), 8G (Mbps port) bandwidth.
27. What is the role of Ethernet Channel Technology?
Increase bandwidth, load balancing, and line backup
28. How do I select a line when the port is set to an Ethernet Channel?
Determine the output link based on the Ethernet source address and destination address of the data frame. The Router performs or operations based on the network address to determine the output of the link.
29. What is the difference between Ethernet Channel Technology and PAgP (Port Aggregation Protocol?
PAgP is an enhanced version of the Ethernet Channel. It supports Spanning Tree Protocol and Uplink Fast on the Ethernet Channel, and supports automatic configuration of Ethernet Channel binding.
Minimum required power supply: 1 2
Packet forwarding rate 18 Mpps 18 Mpps
24 Gbps, 60 Gbps
30. Does the systst4000 series support ISL?
Supported since Supervisor Engine Software Release 5.1.
31. What is the difference between the 4008/2 and 4008/3 redundant power options of the ipvst4000 switch?
There are two power slots on the chassis of the Catalyst4003 switch. The factory comes with a power supply, and the 4008/2 is a redundant power supply customized for it. The Catalyst4006 chassis has three power slots with two power supplies at the factory, and 4008/3 is a dedicated redundant power supply customized for it.
32. Does the layer-3 Switch module of Catalyst 4006 contain Ethernet ports?
No, the layer-3 Switching Module of ipvst4006 contains 32 10/100 adaptive ports and 2 Gigabit ports. In 4003, the original WS-X4232-GB-RJ module can be replaced without affecting the network structure.
33. How to choose the two existing switch modules (Product NO. below) when using the Gigabit Switch module for the Catalyst 4000 Series Modular switch )?
WS-X4418-GB Catalyst 4000 GE Module, Server Switching 18-Ports (GBIC)
The use environments of these two modules are different.
WS-X4306-GB is a 6-port Gigabit Switch module, each port exclusive Gigabit bandwidth, suitable for network trunk, used to connect with a gigabit interface switch; it can also be connected to a server with a gigabit Nic.
The WS-X4418-GB is an 18-port Gigabit Switching Module with two ports providing exclusive Gigabit bandwidth and the other 16 ports sharing 8 GB of Full Duplex bandwidth, but each port can burst to gigabit. This module is suitable for connecting Gigabit servers where servers are concentrated, rather than the network trunk.
34. What is the bandwidth and packet forwarding rate of the Catalyst 6000 series?
The bandwidth of the Catalyst 6500 series can be extended to 256 Gbps, and the packet forwarding rate can be extended to 150 Mpps; the Catalyst 6000 series, as a cost-effective solution, provides 32 Gbit/s of onboard bandwidth and a packet forwarding rate of 15 mpps.
35. How many m dram does the MSFC Of The Catalyst 6000 series require?
The Catalyst 6000 series IOS software is stored in MSFC, which requires 128 m dram. The default configuration already contains 128 m dram.
36. Are there any limitations on the slots on the Catalyst 6000 series?
Except the first slot for the engine, the second slot can be used for backup engines or line cards, and other slots are used for line cards.
37. How many engines does the Catalyst 6000 series have?
The Engine of the Catalyst 6000 series is divided into two types: Supervisor Engine 1 and Supervisor Engine 1A. Supervisor Engine 1A 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, with two Gigabit ports (GBIC required)
WS-X6K-SUP1A-PFC Catalyst 6000 Supervisor Engine1A engine includes two Gigabit ports (GBIC required) and PFC cards
WS-X6K-S1A-PFC/2 Catalyst 6000 Supervisor Engine1A redundancy engine includes two Gigabit ports (GBIC required) and PFC cards
WS-X6K-SUP1A-MSFC Catalyst 6000 Supervisor Engine1A engine includes two Gigabit ports (GBIC required) and MSFC, PFC cards
WS-X6K-S1A-MSFC/2 Catalyst 6000 Supervisor Engine1A redundancy engine with two Gigabit ports (GBIC required) and MSFC, PFC cards
38. Must the backup engine and master engine on the Catalyst 6000 series be consistent?
Yes. The backup engines of the Catalyst 6000 series must be consistent with the master engine. For example, you cannot back up engines without MSFC or FC to engines with MSFC or FC. In addition, WS-X6K-SUP1A-PFC and WS-X6K-SUP1A-MSFC have dedicated backup engines.
The relationship between the master and slave engines is as follows:
Master 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
39. What routing protocols are supported by the Catalyst 6000 series?
The Catalyst 6000 series support the following routing protocols: OSPF, IGRP, VPN, BGP4, IS-IS, RIP, and rip ii;
Supports the sparse and dense modes for multicast PIM;
The supported non-IP routing protocols include NLSP, ipx rip/SAP, ipx vpn, RTMP, Apple Talk VPN, and DECnet Phase IV and V.
40. What network protocols are supported by the Catalyst 6000 series?
6 Mpps IP addresses, IP multicast, and IPX are supported on MSM. The MSFC engine supports 15 mpps of IP, IP multicast, IPX, AppleTalk, VINEs, and DECnet.
41, megast6000 if the engine for the SUP-1A-2GE, how to achieve three layer switching function?
Use MSM. In 6000, only engines with MSFC can implement layer-3 switching through MSFC. In 6000, MSFC cannot be separately ordered.
42. Catalyst? 6000 switch and Catalyst? 6500 what is the difference between vswitches? Can a 6000 switch be upgraded to a 6500 switch?
Catalyst? The bandwidth of the 6000 series switches is 32 GB, while that of the 6500 series switches can be expanded to 256 GB. Because the two series switches use different Backplane Bus structures, the 6000 switch cannot be upgraded to the 6500 series switch.
However, these two series switches use the same switch module.
43. Can I use the chrysanthemum chain stack mode the same as that of the Catalyst3524?
Yes.
44. Do I need to disable the original Spanning-Tree option when Uplink-Fast is configured between switches?
No. Uplink-Fast actually uses a simplified Spanning-Tree algorithm that is compatible with the standard Spanning-Tree. Therefore, you do not need to disable this function.
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