Today i was playing with BGP a little (i found some time to prepare for my CCIP) and here is what i found out:

Suppose you have the following config on a router:

interface Loopback1
 ip address 1.1.1.1 255.255.255.128
!
router bgp 1
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.128
 aggregate-address 1.1.0.0 255.255.0.0 summary-only
 aggregate-address 1.1.1.0 255.255.255.0 summary-only
 neighbor 10.10.10.2 remote-as 2
 no auto-summary

What do you think “sh ip bgp” will show? (please take some time and think about it…)

To be honest, as a first thought i was hoping it would display only the 1.1.0.0/16 summary, which actually “overlaps” the 1.1.1.0/24 summary.

Guess what?

R1#sh ip bgp
BGP table version is 5, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.1.0.0/16       0.0.0.0                            32768 i
s> 1.1.1.0/25       0.0.0.0                  0         32768 i
*> 1.1.1.0/24       0.0.0.0                            32768 i

According to Cisco, in order to aggregate an address, you must have a more-specific route of that address in the BGP table. An if you want the more-specific route to be suppressed, you must use the “summary-only” keyword.

So, if we want to be as strict as possible, in our case we do have a more-specific route in the BGP table (and in the routing table).

R1#sh ip bgp 1.1.1.0/24
BGP routing table entry for 1.1.1.0/24, version 5
Paths: (1 available, best #1, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
  10.10.10.2
  Local, (aggregated by 1 1.1.1.1)
    0.0.0.0 from 0.0.0.0 (1.1.1.1)
      Origin IGP, localpref 100, weight 32768, valid, aggregated, local, atomic-aggregate, best
R1#
R1#sh ip route 1.1.1.0 255.255.255.0
Routing entry for 1.1.1.0/24
  Known via "bgp 1", distance 200, metric 0, type locally generated
  Routing Descriptor Blocks:
  * directly connected, via Null0
      Route metric is 0, traffic share count is 1
      AS Hops 0

Although the aggregation part seems to be working fine (it actually isn’t), the suppression one isn’t. As it seems, an aggregate-address cannot suppress another more-specific aggregate-address, when both are created locally in the same router.

Now, let’s change the config and make it more interesting by removing the “summary-only” keyword from the more-specific aggregate-address :

router bgp 1
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.128
 aggregate-address 1.1.0.0 255.255.0.0 summary-only
 aggregate-address 1.1.1.0 255.255.255.0
 neighbor 10.10.10.2 remote-as 2
 no auto-summary

R1#clear ip bgp *

R1#sh ip bgp
BGP table version is 5, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.1.0.0/16       0.0.0.0                            32768 i
s> 1.1.1.0/25       0.0.0.0                  0         32768 i
*> 1.1.1.0/24       0.0.0.0                            32768 i

What do you think of that? We still have the same output. The more-specific (lower level) aggregate-address is not suppressed, but the more-specific network is (by the 1.1.0.0/16 aggregate-address).

Why is that? Although i’m not sure, looking at the following debugs (after adding another level of aggregation using the “aggregate-address 1.0.0.0 255.0.0.0 summary-only” command and reseting the gp session), i have come to this explanation:

*Mar  1 02:28:52.107: BGP(0): nettable_walker 1.1.1.0/25 route sourced locally
*Mar  1 02:28:52.111: BGP(0): Aggregate processing for IPv4 Unicast
*Mar  1 02:28:52.111: BGP(0): For aggregate 1.0.0.0/8
*Mar  1 02:28:52.111: BGP(0): 1.0.0.0/8 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): sub-prefix : 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Needs to be re-aggregated
*Mar  1 02:28:52.115: BGP(0): 1.0.0.0/8 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): 1.0.0.0/8 aggregate has 1.1.1.0/25 more-specific
*Mar  1 02:28:52.115: BGP(0): 1.0.0.0/8 aggregate created, attributes updated
*Mar  1 02:28:52.115: BGP(0): created aggregate route for 1.0.0.0/8
*Mar  1 02:28:52.115: BGP(0): 1.0.0.0/8 subtree has an entry 1.0.0.0/8
*Mar  1 02:28:52.115: BGP(0): 1.0.0.0/8 subtree has another entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 02:28:52.115: BGP(0): For aggregate 1.1.0.0/16
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): sub-prefix : 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Needs to be re-aggregated
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 aggregate has 1.1.1.0/25 more-specific
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 aggregate created, attributes updated
*Mar  1 02:28:52.115: BGP(0): created aggregate route for 1.1.0.0/16
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.0.0/16
*Mar  1 02:28:52.115: BGP(0): 1.1.0.0/16 subtree has another entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 02:28:52.115: BGP(0): For aggregate 1.1.1.0/24
*Mar  1 02:28:52.115: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): sub-prefix : 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Needs to be re-aggregated
*Mar  1 02:28:52.115: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): 1.1.1.0/24 aggregate has 1.1.1.0/25 more-specific
*Mar  1 02:28:52.115: BGP(0): 1.1.1.0/24 aggregate created, attributes updated
*Mar  1 02:28:52.115: BGP(0): created aggregate route for 1.1.1.0/24
*Mar  1 02:28:52.115: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 02:28:52.115: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 02:28:52.115: BGP(0): Found sub-prefix 1.1.1.0/24:
*Mar  1 02:28:52.115: BGP(0): Revise route installing 1 of 1 route for 1.0.0.0/8 -> 0.0.0.0 to main IP table
*Mar  1 02:28:52.119: RT: network 1.0.0.0 is now variably masked
*Mar  1 02:28:52.119: RT: add 1.0.0.0/8 via 0.0.0.0, bgp metric [200/0]
*Mar  1 02:28:52.119: RT: NET-RED 1.0.0.0/8
*Mar  1 02:28:52.119: BGP(0): Revise route installing 1 of 1 route for 1.1.0.0/16 -> 0.0.0.0 to main IP table
*Mar  1 02:28:52.119: RT: add 1.1.0.0/16 via 0.0.0.0, bgp metric [200/0]
*Mar  1 02:28:52.119: RT: NET-RED 1.1.0.0/16
*Mar  1 02:28:52.119: BGP(0): nettable_walker 1.1.1.0/25 route sourced locally
*Mar  1 02:28:52.119: BGP(0): Revise route installing 1 of 1 route for 1.1.1.0/24 -> 0.0.0.0 to main IP table
*Mar  1 02:28:52.119: RT: add 1.1.1.0/24 via 0.0.0.0, bgp metric [200/0]
*Mar  1 02:28:52.119: RT: NET-RED 1.1.1.0/24

During the initial scanning, the aggregate processing algorithm of BGP doesn’t even check the locally aggregated addresses (is recursive scanning too difficult/dangerous to implement?), because they aren’t in the BGP routing table at the time of scanning (i guess if the scanning was happening from more-specific to less-specific, it would find them). So it checks only the networks that are injected into BGP through the 3 known ways (network command, redistribution, other ASs). In our case, every configured aggregate-address is aggregating and suppressing only the locally configured more-specific network. Specifically, the more-specific local network is aggregated & suppressed 3 times, one for each aggregate-address definition.

The result?

R1#sh ip bgp
BGP table version is 6, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 1.0.0.0          0.0.0.0                            32768 i
*> 1.1.0.0/16       0.0.0.0                            32768 i
s> 1.1.1.0/25       0.0.0.0                  0         32768 i
*> 1.1.1.0/24       0.0.0.0                            32768 i

If we add the less-specific aggregate after the BGP has already started, we get different debug logs:

*Mar  1 00:05:26.995: BGP(0): Aggregate processing for IPv4 Unicast
*Mar  1 00:05:26.995: BGP(0): For aggregate 1.0.0.0/8
*Mar  1 00:05:26.995: BGP(0): 1.0.0.0/8 subtree has an entry 1.1.0.0/16
*Mar  1 00:05:26.999: BGP(0): sub-prefix : 1.1.0.0/16
*Mar  1 00:05:26.999: BGP(0): Needs to be re-aggregated
*Mar  1 00:05:26.999: BGP(0): 1.0.0.0/8 subtree has an entry 1.1.0.0/16
*Mar  1 00:05:27.003: BGP(0): 1.0.0.0/8 aggregate has 1.1.1.0/25 more-specific
*Mar  1 00:05:27.007: BGP(0): 1.0.0.0/8 aggregate created, attributes updated
*Mar  1 00:05:27.007: BGP(0): created aggregate route for 1.0.0.0/8
*Mar  1 00:05:27.011: BGP(0): 1.0.0.0/8 subtree has an entry 1.0.0.0/8
*Mar  1 00:05:27.011: BGP(0): 1.0.0.0/8 subtree has another entry 1.1.0.0/16
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.0.0/16: not suppressed
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/24: not suppressed
*Mar  1 00:05:27.011: BGP(0): For aggregate 1.1.0.0/16
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.0.0/16
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has another entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): sub-prefix : 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): Needs to be re-aggregated
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.0.0/16
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has another entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 aggregate has 1.1.1.0/25 more-specific
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 aggregate updated
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has an entry 1.1.0.0/16
*Mar  1 00:05:27.011: BGP(0): 1.1.0.0/16 subtree has another entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/24: not suppressed
*Mar  1 00:05:27.011: BGP(0): For aggregate 1.1.1.0/24
*Mar  1 00:05:27.011: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): sub-prefix : 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): Needs to be re-aggregated
*Mar  1 00:05:27.011: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): 1.1.1.0/24 aggregate has 1.1.1.0/25 more-specific
*Mar  1 00:05:27.011: BGP(0): 1.1.1.0/24 aggregate updated
*Mar  1 00:05:27.011: BGP(0): 1.1.1.0/24 subtree has an entry 1.1.1.0/25
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/25: suppressed
*Mar  1 00:05:27.011: BGP(0): Found sub-prefix 1.1.1.0/24:
*Mar  1 00:05:27.011: BGP(0): Revise route installing 1 of 1 route for 1.0.0.0/8 -> 0.0.0.0 to main IP table
*Mar  1 00:05:27.011: RT: add 1.0.0.0/8 via 0.0.0.0, bgp metric [200/0]
*Mar  1 00:05:27.011: RT: NET-RED 1.0.0.0/8

This time, all the existing more-specific aggregates are scanned, but they are clearly not suppressed.

According to RFC 4271:

3.2.  Routing Information Base

   The Routing Information Base (RIB) within a BGP speaker consists of
   three distinct parts:

      a) Adj-RIBs-In: The Adj-RIBs-In stores routing information learned
         from inbound UPDATE messages that were received from other BGP
         speakers.  Their contents represent routes that are available
         as input to the Decision Process.

      b) Loc-RIB: The Loc-RIB contains the local routing information the
         BGP speaker selected by applying its local policies to the
         routing information contained in its Adj-RIBs-In.  These are
         the routes that will be used by the local BGP speaker.  The
         next hop for each of these routes MUST be resolvable via the
         local BGP speaker's Routing Table.

      c) Adj-RIBs-Out: The Adj-RIBs-Out stores information the local BGP
         speaker selected for advertisement to its peers.  The routing
         information stored in the Adj-RIBs-Out will be carried in the
         local BGP speaker's UPDATE messages and advertised to its
         peers.

...
   The Decision Process takes place in three distinct phases, each
   triggered by a different event:

      a) Phase 1 is responsible for calculating the degree of preference
         for each route received from a peer.

      b) Phase 2 is invoked on completion of phase 1.  It is responsible
         for choosing the best route out of all those available for each
         distinct destination, and for installing each chosen route into
         the Loc-RIB.

      c) Phase 3 is invoked after the Loc-RIB has been modified.  It is
         responsible for disseminating routes in the Loc-RIB to each
         peer, according to the policies contained in the PIB.  Route
         aggregation and information reduction can optionally be
         performed within this phase.

...
9.2.2.2.  Aggregating Routing Information

   Aggregation is the process of combining the characteristics of
   several different routes in such a way that a single route can be
   advertised.  Aggregation can occur as part of the Decision Process to
   reduce the amount of routing information that will be placed in the
   Adj-RIBs-Out.

If someone else can provide a better (preferred technical) explanation for both cases, i would be very happy to hear it.

Btw, someone must tell Cisco to write more detailed docs :
“Aggregation applies only to routes that exist in the BGP routing table. An aggregated route is forwarded if at least one more specific route of the aggregation exists in the BGP routing table”

New and Updated Cisco Certification Logos

The Learning@Cisco organization is pleased to introduce new logos for its Cisco Career Certification Program. The logos were designed with input from the Cisco certified community, and represent the prestige and dedication defined by the program. Effective January 12, 2009, all certificates and plaques will include the new logos.

The new logos identify all levels of Cisco Career Certifications. In addition, all technology tracks are identified, allowing current and future professionals to distinguish themselves in the workplace and throughout the IT industry.

*Certified individuals can access the new logos for download by logging into the Certifications Tracking System at: www.cisco.com/go/certifications/login

Question 1: CCIE symbol of what?

Answer: CCIE is Cisco-certified experts in interconnection networks. At the same time, is currently the most advanced technological capabilities Cisco certification.

Question 2: CCIE certification what is the procedure?

A: CCIE certification program is recognized Cisco introduced the industry’s best experts in the interconnection network of an advanced certification program.

Question 3: CCIE certification program provides a what?

Answer: CCIE Certification Program offers:

“Expert” the definition of technical knowledge and competence

Assessment of the authority of such knowledge and ability of the method

The quality of services as those “best-level” engineer of target demand.

Question 4: complete this certification process will Certified Engineer What are the benefits?

A: The CCIE certification process to complete the unique advantages:

Industry-recognized-CCIE is the industry’s recognition of the interconnection network of industry in the high-quality technical experts.

-CCIE special technical support from Cisco can be automatically second-class experts. This will allow them to experience all the known problems experienced direct access to Cisco technical experts.

CCO access and other CCIE via E-mail in the form of direct participation in CCIE Forum.

CCIE upgrades can be only a conversation topic to get CCIE training invitation.

Question 5: In order to reap Carpenter eligible to participate in CCIE certification exams, I have to attend a series of required training courses?

A: Not really. Cisco has identified and recommended routing and switching on a series of training courses, they are not mandatory. However, interconnection network industry experience is very useful.

Question 6: There are lab exam training?

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Question 9: Sylvan Prometric written how?

A: Sylvan Prometric is a three-hour written multiple-choice exam. Remember, for the CCIE Routing and Switching classes, the examination subjects number is 350-001; for Internet service provider (ISP) dial-up class CCIE, the examination subjects number is 350-004; for wide area network (WAN) type CCIE, the examination subjects number is 350-007.

Question 10: Preparing CCIE written and lab exam What is the best way?

A: In addition to reading the contents listed in the table, Cisco recommends a series of router / switch as well as the configuration IP (BGP, OSPF, RIP, IGRP, EIGRP), LAN / WAN, ISDN, RSRB, and DLSW experimental content routing protocols access to skilled master experience.

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A: Cisco now offers a lot of training in training centers, but at varied levels, the choice of training centers, when do have to be careful, the key is to choose their own training center.

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So, since everyone to participate in training, the choice of training centers, they must be careful to not only look at price, more importantly, teachers, laboratory equipment, environment, management and other factors.

5. Q: I have the ability to participate in Cisco CCNA training and certification do?

A: Cisco’s CCNA curricula, it is quite simple. But it also requires a certain basic knowledge, such as the basics of networking, such as: ISO’s OSI reference model for the understanding, TCP / IP protocols. If we do not have confidence on the basis of their own, can go to Galaxy training center, the communication with teachers and to test, so you’ll have at the end of the.

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(B) Frame Relay (FRAMERELAY) Application: CCNA certification exam as the Frame Relay Wide Area Network (WAN) part of the test content. You will encounter a large number of the test are the contents of frame relay. Therefore, you must be prepared to pay particular attention to the frame relay learning.
(3) ISDN issues: to know, such as TE-1, TE-2, NT-1, U interface (U-INTERFACE), B-CHANNAL, D-CHANNAL and a number of sub-channel (SUB-CHANNAL) and other terms (ISDN related to a particularly large number of terms and abbreviations, you must know the meaning and function of each), to understand the difference between BRI and PRI.
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IT certification of sentiment: the certificate and ability in the end who is more important?
Certification is very important? Some say: “That, of course, is not how to prove their level of certification?” Others say: “not necessarily the actual capacity of the most important.”
Both answers are probably right, but incomplete. On this topic, I would talk about according to their own learning experiences and understanding of the views of the certification, for your reference:
1, the certificate of true and false
Broadly speaking, at this stage of employment, the certificate is still important, the certificate is the ability to abstract reflection of the learning process and results proved that without the certificate, you can not prove that! Maybe you really are strong, no matter how good you say , others my heart I will not see you too, Just think, one holding a high school graduation certificate and a master’s degree candidates graduate student to work with a technology-based, others more fancy Who? certificate must exist a certain historical period , we can not deny the importance of the certificate, as the same as university diplomas issued by the State Education Commission.
Certification is narrow, such as network technologies such as professional certification such as MCSE, CCIE, CCNP, etc., we must be clear what brought about such a certification, what? From the firm’s point of view, is undoubtedly of interest to maximize the introduction of Networking Academy, training, certification bodies, the most basic intention of these strategies is to simply promote the visibility of their products and expand market size, when they come out from the university college students who served as XX in the XX business office, business, once there is demand, his first thought was XX vendor network products (of course, rule out other external factors, complete departure from the individual’s original idea), he became the most powerful factory sales. Up from a personal point of view is that no doubt would like to improve their technical level, while increasing income to improve their living conditions for themselves to find a satisfactory job! Revenue base, naturally do not have to say much more. However, our technology is to improve it? On the surface, yes! You say that CCIE and CCNA, which enhanced technical capabilities? Needless to say: CCIE! But the CCIE network technology is really an expert? I see not, especially now, the examination of water I do not have to say, we all know. As long as the network technology have a certain interest in the same time, the people will be willing to spend IE! Our company had a brother, I took the test three times, only narrowly passed, it took two to three thousand dollars, even more unfortunately, are getting the dream of a certificate of employment on the road is not so bon voyage. The most important thing is do not forget, we are on the application of network technology, not development, is to put other people’s ideas by practical application of the physical environment go! You heard, driving F-22 pilots flying specialists? Maybe he is the future, but as long to open the aircraft, there is no person that he is an expert. Most people who go into space called the astronauts. Designed by others a knock on the side of the command to re-engineer, at most, to know the structure and forwarding packets principle one could call specialists? Some far-fetched. Cisco 642-436
At the same time, the network application is from a single business model to a multi-business model to expand, has just passed Routing & Switching CCIE’s brother
Brother, do you understand speech? Do you understand the media? Do you understand safe? You know Unix, Linux, Oracle do? Do not know!, But users have such a demand, how should I do? Learn 呀. Do not think they have been practicing to the highest state of network technology, we need to learn many things in too much.
2, capacity is the most important
On this topic, I can give an example to explain that in 2000 I passed the HCSE, but to get the certificate the first 6 days, I went to do a special CISCO systems integrator, to work the first day, to the company’s bench has not yet firmly secured, the boss sent me sent to a company, said it was exactly one item, very anxious to be resolved quickly. I am also a person to go. Really, really do not mind the end of that time, the heart speak, is over, not even familiar with the products, no chance! That’s no way Yeah, bite the bullet and boarded the plane.
Who knows to which see, I dumbfounded, almost no paralysis continues, routers, switches, self-suffice it to say, there are seven sets PIX firewall, a lot of wireless AP, IP phone, what is there … …. Do not say these things I’ve seen have not even heard of hearing. How to do this time? Tell customers that I Gaobu Ding? Called the boss that I learned just routing switching, the other could not find? Can you? Can not. So what do, do it! I have a little calm and a bit and become a deep breath and began to examine the user the current network conditions, ask customer demand, which know the trouble is still behind the demand of customers is simply too much: the headquarters and other Division through firewalls VPN, through the GRE tunnel using the OSPF routing protocol to achieve dynamic routing at the same time to enable IPsec to encrypt data, wireless AP on the division of VLAN, IP phones and PSTN interworking … … I Kuangyun!
I carefully write notes to the existing network equipment configuration Copy down the new device model, name written down. Back to the hotel looked just write something really very complicated, finally sorted out the structured. But time is pressing, I can not neglect, drill into the interconnect line, crazy look for materials, to find documents, in conjunction with their theoretical knowledge, sorting out the project implementation plan! Behind the things that is not to say, the natural hardships and difficulty, in the not solve the problem, I always sky nonsense, but always saved the day. Half a month later, the project finally completed! Customer satisfaction survey form filled out is: very satisfied. Acceptance of course, no problem (of course also have my Huyou effort, ha ha), but I have physically and mentally exhausted, I am thin. To get acceptance in the report, I was lying in bed in the hotel a myriad of thoughts: I have the certification exam brought me what? An easy? No, just a learning opportunity.
Said here, some would say: If you do not have the certificate, others do not give you the opportunity to learn! Yes, but it is also precisely that question: the certificate is only recruited to work in your work the moment, other times worthless! certification exam that manufacturers not important, it is important you do not really understand the technology, can solve the problem.
Today I have learned a lot of things other than certification. In addition, the network technology is moving towards international standardization, each device manufacturers must comply with these standards! So for us to seriously study the technology is the most important of these standards, rather than blindly pursuing the vendor certification .
For access to a manufacturer-certified engineers, you can not exclude other manufacturers of equipment, for example, you are xx-certified engineer, if you are CISCO network equipment such as a world-class manufacturing things will not use, would not be too sorry it? If you are a CISCO certified engineer, much less supercilious.
Another point worthy of our attention has been the proliferation of network technology certification, many college graduates have gotten into the certified tide of years, is bound to result in supply exceeding demand in one day, so many people crowded into a corridor go rush of a share, then we have a value? So, I advise those brothers and sisters in computer science, network technology, certification of other professional people that there should be considered a shortcut, but not necessarily for you, and should strengthen the basic knowledge of learning, improve thinking, such as learning the language as far as possible to engage in the development, can not go to test, what kind of certification is needed. The pressure of employment, a positive hit our generation, those who wanted to test certification exam has not yet, or are being test, and ask you to consider carefully, certification, after he was in the end give you what?

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CiscoCertifiedDesignAssociate

Certification of basic skills
CCDA certified personal networks of primary level of design technology. CCDA who pass the exam receive certification and can be caught using business cards CCDA tag.
CCDA is divided into a chunk:
★ routing and switching Pass4sure 640-821
In order to help examinees prepare for the exam, Cisco Partners in Learning provides the following services:
• Instructor lectures and online training
• Online Forum
• via the Internet, a remote laboratory experiments practical ability to improve other information can be found in the Cisco Learning bookstores.
Note: You can directly participate in CCDA certification examination and obtain a certificate
CCDA Certification Benefits
To sum up, Cisco certification can confirm the level of the certificate holder, by certified high level of expertise to enhance the credibility of their professional authority. CCDA certification is mainly to meet the less than 500 nodes in a simple SOHO market needs and have a simple LAN, routed WAN, switched LAN network of medium-sized companies need to design knowledge.
CCDA professional skills
• decided to customer network implementation, security, capacity and scalability requirements
• designed to meet customer demand network architecture
• the advantages of the design to meet customer needs
• develop and test a prototype network in order to ensure that the design and provide convincing evidence of customer satisfaction
CCDA positions include:
• Primary Network Design Engineer
• Junior System Engineer
• Cisco’s sales channel partners, senior sales representative
The road leading to CCDA Certification
1. Meet the prerequisite for the Cisco Certified Network Design (DCN) is designed to prepare candidates for the CCDA teaching materials. Courses can be found in the study site, description, and curriculum objectives.
2. Determine your learning needs necessary for the study and a prerequisite for DCN
3. Self-study and lay the basis for studying the site in bookstores to buy Cisco Learning Connection Cisco Training CD (ITM CD), to be familiar with terminology, protocols and equipment
4. Online training and instructor training to develop skills to understand instruction DCN’s online training and mentoring classes, and to choose your method of teaching can be found in the study site to be a Cisco Learning Partner-related services
5. DCN exam to participate in the site can be found in the relevant certification exam information, you can register online to participate in a safe environment simulation test. Elderly persons who pass the exam receive CCDA certificate and be able to use business cards CCDA tag.

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Cisco Certification Study Notes 1
Chapter 1 Troubleshooting Methods
    First, the complexity of the network
    General network, including routing, dial-up, switching, video, WAN (ISDN, Frame Relay, ATM, …), LAN, VLAN, …
    2, fault handling model
    1, define the problem (Define the Problem)
    Detailed and precise description of failure symptoms and potential causes
    2, collecting detailed information (Gather Facts) R> source of information: the key to user, network management systems, router / switch
1) identify the symptoms:
    2) to reproduce the failure: validation failure still exists
    3) to investigate failure Frequency:
    4) to determine the scope of failure: There are three ways to establish the scope of failure
    a from the outside to inside Fault Handling (Outside-In Troubleshooting): usually applied to multiple hosts can not connect to a server or server set
    b from the inside to the outside Troubleshooting (Inside-Out Troubleshooting):
    c half-point Fault Handling (Divide-by-Half Troubleshooting)
 3, consider the possible cases (Consider Possibilities) caused by failure to consider the possible reasons for
 4, establish a plan of action (Create the Action Plan)
 5, the deployment of action plans (Implement the Action Plan)
Used to correct the causes of network failure. Department as the source from the most trouble, and come up with ways to complete each step, check whether the failure to resolve
6, observe the action plan to implement the results of (Observe Results)
    7, where action plans can not solve the problem, repeat the above procedure (Iterate as Needed)
    3, record changes made to
    The adoption of action plans to address the problem, suggested that record as part of the fault handling, record all the configuration changes.

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CCNA Certification Introduction
CCNA certification is the Cisco certification system in the most elementary certification at the same time it is to obtain CCNP certification, CCDP, and CCSP certification certification a necessary condition for (CCIP Certification, CCIE certification is not mandatory), and many Cisco professional certification (Cisco Qualified Specialist) is also to require candidates must first possess the CCNA certification.
After-sales engineers are Cisco Certified CCNA certification system entry certification, through the CCNA can prove you have mastered the basic knowledge of the network, and can the initial installation, configuration and operation of Cisco routers, switches, and simple LAN and WAN. CCNA certification that certified personnel have for the small office / home office (SOHO) market linkages that the basic technology and knowledge. CCNA certified professionals can be passed in small networks (100 or 100 nodes below) in installation, configuration and operation of LAN, WAN and dial access services. They can use the agreement include (but are not limited to): IP, IGRP, IPX, Serial, AppleTalk, Frame Relay, IP RIP, VLAN, RIP, Ethernet, Access Lists.
A prerequisite to obtain CCNA certification
Candidates do not need any certificate holder can apply for CCNA, candidates the same time, age, education, foreign language is not mandatory for the average water;
CCNA certification exams
Now take the exam there are two ways: one, to participate in the 640-801 CCNA exam; 2, to participate in the 640-821 INTRO and 640-811 ICND 2 exams; you can buy the materials at the following site: http://www.pass4sure.com/

CCNA certification is valid
CCNA certification is valid for three years, three years later required to attend re-certification (Recertification) examination, if you are in this two-year period to qualify as a higher level of Cisco certification, CCNA certification is valid for automatic updates.
CCNA Re-Certification Exam
After the expiry must attend 640-811 ICND exam, or participate in any one section CCNP, CCDP, CCIP, CCSP exam, and then, or participate in any of a Cisco Qualified Specialist Division prefix 642-XXX exam.
Comparison of MCSE and CCNA
First, briefly explain, MCSE and CCNA is a certification in both directions, there is no direct comparability between the two more complementary nature of knowledge.
From the basic requirements of view: CCNA study time is short
The most people, CCNA involved in the foundation of network knowledge and equipment, but also the support of CISCO equipment, learning cycle in about 1-3 months or so
MCSE daily use more approachable, and can be achieved most of its stand-alone certification exam requirements, the learning cycle of seven subjects for at least 3-6 months.
From the learning costs of view: CCNA low-cost
CCNA only involves an examination, the examination fee at 20 dollars, if the self-study, then, together with books and teaching materials cost no more than 30 U.S. dollars;
While there are seven exams MCSE, optical examination fees in respect of 45 U.S. dollars.
From the direction of view of employment: CCNA are highly specialized
CCNA employment direction system integration, network installation and maintenance and so on debugging.
MCSE suitable positions, there are system administrators, network administrators, and so on.
From the work content perspective: CCNA required hands-on capacity
CCNA is a simple CISCO based network equipment debugging and knowledge;
MCSE is for the Windows environment, network, system management, configuration, maintenance;
The general public, we recommend students for certification in terms of need, you can choose CCNA, time is short, quick, cost-effective.

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Cisco Certification System

CPE (Cisco Product Essential) and CSE (Cicso Solution Essential) to obtain CPE, CSE certificate you:
Cisco has been a systematic understanding of the characteristics of a full line of networking products can be targeted for the customer design a set of solutions that enables customers to get what they really want, so you work in sales can be handy, stand undefeated and the to
Cisco Certified System Engineer sale
Cisco Certified Network Associate (CCNA): This certification proves that you have mastered the basic knowledge of the network, and can the initial installation, configuration and operation of Cisco routers, switches, and simple LAN and WAN.
Cisco Certified Network Professional (CCNP): CCNP is a Cisco grant a permit system in the mid-level certification, ranging between CCNA and CCIE. CCNP should be able to use complex protocols and technologies to install, configure, operate the network, and with diagnosis and troubleshooting capabilities.
Cisco Certified Internet Expert (CCIE): This certification is the highest Cisco certification system, a certification is a variety of network you have the knowledge and technology, and Cisco product installation, operation and configuration of the well accepted.
Cisco pre-sales engineer certification system
Cisco Certified Design Associate (CCDA): This certification is the Cisco pre-sales design support engineer for the first certification. Can prove that you have been able to use the network should have the knowledge, equipment, installation, configuration and operating skills on a simple LAN, WAN, and switched LAN design.
Cisco Certified Design Professional (CCDP): This certification is the Cisco pre-sales design support engineer for the second certification, and the most advanced authentication. Should be able to use the network should have the knowledge, equipment installation, configuration and operating skills to complex LAN, WAN, and switched LAN design.

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