Archive for the ‘Computer Certification’ Category
When you earned your CCNA, you thought you learned everything there is to know about RIP. Close, but not quite! There are some additional details you need to know to pass the BSCI exam and get one step closer to the CCNP exam, and one of those involves RIP update packet authentication.
You’re familiar with some advantages of using RIPv2 over RIPv1, support for VLSM chief among them. But one advantage that you’re not introduced to in your CCNA studies is the ability to configure routing update packet authentication.
You have two options, clear text and MD5. Clear text is just that – a clear text password that is visible by anyone who can pick a packet off the wire. If you’re going to go to the trouble of configuring update authentication, you should use MD5. The MD stands for “Message Digest”, and this is the algorithm that produces the hash value for the password that will be contained in the update packets.
Not only must the routers agree on the password, they must agree on the authentication method. If one router sends an MD5-hashed password to another router that is configured for clear-text authentication, the update will not be accepted. debug ip rip is a great command for troubleshooting authenticated updates.
R1, R2, and R3 are running RIP over a frame relay cloud. Here is how RIP authentication would be configured on these three routers.
R1#conf t
R1(config)#key chain RIP
< The key chain can have any name. >
R1(config-keychain)#key 1
< Key chains can have multiple keys. Number them carefully when using multiples. >
R1(config-keychain-key)#key-string CISCO
< This is the text string the key will use for authentication. >
R1(config)#int s0
R1(config-if)#ip rip authentication mode text
< The interface will use clear-text mode. >
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OSPF route redistribution is an important topic on the BSCI exam, and it’s a topic full of details and defaults that you need to know for the exam room and the job. To help you pass the BSCI exam, here’s a quick review of some of the OSPF route redistribution basics.
To see if a router is an ABR or ASBR, run show ip ospf. This also displays any routes being redistributed into OSPF on this router.
R1#show ip ospf
Routing Process “ospf 1″ with ID 1.1.1.1
Supports only single TOS(TOS0) routes
Supports opaque LSA
It is an area border and autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
rip, includes subnets in redistribution
When redistributing RIP into OSPF, the “subnets” option is needed to include subnets in redistribution. When redistributing OSPF into RIP, a seed metric must be specified. (OSPF gives redistributed routes a default metric of 20 – this can be changed, but a seed metric does not have to be set.)
R1(config)#router ospf 1
R1(config-router)#redistribute connected
% Only classful networks will be redistributed
R1(config-router)#redistribute connected subnets
R1(config-router)#redistribute rip subnets
R1(config-router)#router rip
R1(config-router)#redistribute connected metric 1
R1(config-router)#redistribute ospf 1 metric 1
As a CCNP candidate, as a CCNA, and in getting ready to pass the BSCI exam, you may be tempted to breeze through your static route studies, or even skip them! That’s because static routes are easy enough to configure, and as long as you remember the syntax of the ip route command, you’re in good shape.
But there’s one vital detail regarding static routes that many exam candidates miss. That’s because many CCNA and CCNP books say “the administrative distance of a static route is 1″, but that is not quite accurate.
You know from your CCNA studies that the ip route command is used to create a static route, and that you have the option of configuring a local exit interface or a next-hop IP address at the end of the command. However, the administrative distances are not the same. The AD of a static route that uses a local exit interface is zero! (That’s because the router considers a static route with a local exit interface to actually be a directly connected network.) The AD of a static route with a next-hop IP address is 1.
Therefore, if the router has the following two ip route statements to consider…
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There was a time, before phone cards, when long distance and international calls – even to friends and relatives – required a good amount of preparations. Everyone making international calls had to back-calculate:
• How much money do I want to spend on this international call?
• How many minutes does it give me?
• And what do I need to talk for this many minutes?
Sound funny?
Yes it does in today’s world, where phone cards are making long distance and international calls cheaper day by day. Phone cards were first introduced to make long distance calling easy and convenient. One could make long distance and international calls from any phone using these cards. Then came the price war between the long distance operators and the cost of calling using phone cards started coming down significantly compared to post-paid phone connections.
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