blockhead's Blog
Category Computers-and-Technology:Certification-Tests
One of the most confusing parts of beginning your Cisco studies is keeping all the cable types separate in your mind, and then remembering what they’re used for. This often occurs when a CCNA or CCNP candidate starts putting together their own home practice lab, and they suddenly realize that they have the equipment to run labs, but not the cables. With this in mind, here are some common Cisco cable types and their primary use. First, there’s the regular old “straight-through cable”, so named because the eight wires inside the cable go straight through the wire. While the wires may be twisted inside to reduce electromagnetic interference (EMI), the wire that’s connected to Pin 1 on one end is connected to Pin 1 on the other end, and so on. In a home lab, a straight-through cable is often used to connect a switch port to an Ethernet port on a router, with a transceiver attached to the Ethernet port. Straight-through cables are also good for connecting a BRI interface to an ISDN simulator. The “crossover cable” is so named because the wires do cross over between pins. This allows the devices to both send and receive at the same time, and crossover cables are a must for directly connecting ports on Cisco switches to create a trunk. The “rollover cable” allows you to connect directly to a Cisco console port with your laptop or PC. This is the blue cable that comes with new Cisco devices, and it’s the one that engineers tend to hold on to with their lives. Without a rollover cable (also commonly called a “console cable”), you can’t connect your laptop directly to a Cisco device. Finally, there’s the DTE/DCE cable. To create a frame relay cloud in your home lab (using one of your Cisco routers as a DCE), or to directly connect two Cisco routers via their serial interfaces, you will need a DTE/DCE cable. Remember that the DCE interface will need to supply clockrate to the DTE interface. The different cable types can be confusing when you first read about them, but after tearing down or building your home lab a few times, you’ll definitely have them straight come test day! Best of luck in your lab and your exams. Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.
For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNA exam with The Bryant Advantage!  cisco, certification, ccna, ccnp, ccie, exam, pass, cable, dte/dce, chris, bryant, 12933, console
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DNS behaviors of a Cisco router are important topics for both the CCNA exam and real-world production networks, and you probably didn't know there were so many DNS details before you began studying for the exam! In this tutorial, we'll look at the ip name-server command and its proper usage. When a command is mistyped on a Cisco router, the default behavior of the router is to attempt to resolve it via DNS. First, the router looks for an IP Host table on the local router to perform this resolution – that’s what the “translating” word in the output is referring to. If there’s no IP Host table or the IP Host table doesn’t contain an entry for what you typed, the router will send a broadcast in an attempt to resolve this name through a remote DNS server. To prevent this broadcast, enter the global command no ip domain-lookup. Of course, to use DNS to resolve hostnames, ip domain-lookup would have to be reenabled if it’s been turned off. R2#contin Translating 'contin'...domain server (255.255.255.255) % Unknown command or computer name, or unable to find computer address A command is mistyped as “contin”. The Cisco router’s default behavior is to resolve this entry locally via an IP Host table, which isn't present on the router. A broadcast is then sent out to find a DNS server to perform the name resolution. The DNS lookup attempt must time out before the configuration can continue. R2#conf t R2(config)#no ip domain-lookup R2#contin Translating 'contin' % Unknown command or computer name, or unable to find computer address With “no ip domain-lookup” configured, the router doesn’t attempt to find a remote DNS server. It sees there is no local resolution configured and almost immediately sends a message to the console that the name can’t be resolved. R2#conf t R2(config)#ip domain-lookup R2(config)#ip name-server 10.1.1.1 R2#contin Translating 'contin'...domain server (10.1.1.1) A DNS server is installed on the network with the IP address 10.1.1.1. DNS lookup is reenabled with the command ip domain-lookup, and the IP address of the DNS server is specified with the ip name-server command.
It's just that easy to tell a Cisco router exactly where the DNS server is! Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.
You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website.
For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, visit the website and download your free copies. You can also get FREE CCNA and CCNP exam questions every day! Get your CCNA study guide from The Bryant Advantage! cisco, ccna, exam, free, pass, dns, ip, name, server, domain, lookup, broadcast, stop, bryant, 12933
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In your BCMSN / CCNP exam study, it's easy to overlook some of the details of Spanning Tree Protocol (STP). After all, you learned all of that in your CCNA studies, right? Not necessarily! While some of the BCMSN material will be a review for you, there are some details regarding familiar topics that you need to learn. That includes the timers for STP - Hello Time, MaxAge, and Forward Delay. You may remember these timers from your CCNA studies as well, and you should also remember that these timers should not be changed lightly. What you might not have known is that if you decide to change any and all of these timers, that change must be configured on the root bridge! The root bridge will inform the nonroot switches of the change via BPDUs. Hello Time is the interval between BPDUs, two seconds by default. Forward Delay is the length of both the listening and learning STP stages, with a default value of 15 seconds. Maximum Age, referred to by the switch as MaxAge, is the amount of time a switch will retain a BPDU's contents before discarding it. The default is 20 seconds. The value of these timers can be changed with the spanning-tree vlan command shown below. Verify the changes with the show spanning-tree command. SW1(config)#spanning-tree vlan 1 ? forward-time Set the forward delay for the spanning tree hello-time Set the hello interval for the spanning tree max-age Set the max age interval for the spanning tree priority Set the bridge priority for the spanning tree root Configure switch as root SW1(config)#spanning-tree vlan 1 hello-time 5 SW1(config)#spanning-tree vlan 1 max-age 30 SW1(config)#spanning-tree vlan 1 forward-time 20 SW1(config)#^Z SW1#show spanning-tree vlan 1 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000f.90e1.c240 This bridge is the root Hello Time 5 sec Max Age 30 sec Forward Delay 20 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 000f.90e1.c240 Hello Time 5 sec Max Age 30 sec Forward Delay 20 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Fa0/11 Desg FWD 19 128.11 P2p Fa0/12 Desg FWD 19 128.12 P2p Again, you should always take great care in changing these timers. Those defaults are set for a reason - helping to prevent switching loops! Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNP and CCNA tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCNA / CCNP exam questions! Details are on the website. For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, just visit the website! You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNP exam with The Bryant Advantage! ccnp, bcmsn, certification, exam, pass, free, stp, spanning, tree, protocol, forward, delay, timer Sorry, but the blog post could not be located. ccna, ccnp, bsci, bcran, free, exam, tutorial, span, tree, protocol, router, switch, ios, 5000 Sorry, but the blog post could not be located. |
