CCNA Certification: Three Occasions To Reload Or Reopen A Cisco Router Interface

Passing the CCNA certification exam means that you know how to configure and troubleshoot a Cisco router instead of using what I call the "hope method" - you know, "Let's reload the router and hope that takes care of it." The majority of Cisco router configurations take effect without the need for a reload, but every once in a while you just have to reload a router or shut and reopen an interface. Let's take a look at three such scenarios.

The first is when you change an OSPF Router ID from its default. For the new RID to take effect, you must either reload the router or clear the OSPF process, which means that all existing adjacencies will come down. Cisco routers are kind enough to tell you this with the following message after you configure a new RID: "Reload or use "clear ip ospf process" command, for this to take effect".

In a previous tutorial, I showed you how to configure an Etherchannel. You have to place each port into the Etherchannel with the channel-group command, and if you do so individually, some of the ports may go into error-disabled state, or "err-disable". This can also happen as a result of port security enforcement. You can see this with the show interface command:

sw1#show int fast 0/1

FastEthernet0/1 is down, line protocol is down (err-disabled)

A syslog message putting that port into err-disabled state will look like this:

04:10:23: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po1, putting Fa0/1 in err-disable state

If this happens during an Etherchannel configuration, just finish the config and then shut and reopen the ports in err-disabled state. They'll come back up and be placed into the Etherchannel.

Finally, our old friend the SPID often makes us shut and reopen the BRI interface. If the BRI interface is open and you configure SPIDs on it, the SPID can be absolutely correct and you'll still see this in the output of show isdn status:

spid1 configured, spid1 NOT sent, spid1 NOT valid

At least the Cisco router puts "NOT" in caps, right? It's easier to see that way! With SPIDs, before you call the service provider or check the SPID you entered about 40 times, just shut and reopen the interface. That usually does the trick.

When you earn your CCNA certification, that means that you know what you're doing instead of hoping that you do - and part of that knowing is knowing when a simple reload or open/shut will take care of the issue.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of over 200 free certification exam tutorials, including CCNA certification training articles. His exclusive CCNA study guide is also available!

Visit his blog and sign up for Cisco Certification Central, a daily newsletter packed with CCNA, Network+, Security+, A+, and CCNP certification exam practice questions! A free 7-part course, ?How To Pass The CCNA?, is also available, and you can attend an in-person or online Cisco CCNA training boot camp with The Bryant Advantage!

 

Cisco CCNP Certification Training: What's New On The BSCI 642-901 Exam

CCNP certification is getting a new look at the end of 2006. The BSCI and BCMSN exams are being updated, and the CIT and BCRAN exams are being retired. Let's take a look at what to expect from the new BSCI exam.

According to Cisco's exam blueprint - admittedly a very broad blueprint at this time - the major new topics are IP version 6 (IPv6) and multicasting. The addition of these two topics will make an already demanding Cisco certification exam that much tougher, but this is a great change for the exam and for the candidate. IPv6 is just going to become more and more prevalent in today's networks, and multicasting is as well.

Multicasting for the Cisco CCNP BSCI exam is going to go far beyond what you learned about it in your CCNA studies. For the new BSCI exam, you'll need to know the different methods of creating multicast groups as well as assigning members to them. This material was previously limited to CCIE-level books, and while I don't look for the questions to be as hard as the CCIE written exam, multicasting is not an easy topic and should not be taken lightly by the CCNP candidate in 2007.

One major CCNP exam topic that isn't going anywhere is BGP. The Border Gateway Protocol has been a big part of previous BSCI exams, and that looks to continue.

If you're pursuing your CCNP certification in 2007, be sure to monitor Cisco's website for additions to the CCNP blueprint. It's obvious that Cisco has raised the bar for CCNP certification, and earning this important Cisco certification will in turn raise your market value and networking knowledge like never before. Watch for future tutorials examining the other three new CCNP exams!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of over 100 free certification exam tutorials, including Cisco CCNA certification test prep articles. His exclusive Cisco CCNA study guide and Cisco CCNA training is also available!

Visit his blog and sign up for Cisco Certification Central, a daily newsletter packed with CCNA, Network+, Security+, A+, and CCNP certification exam practice questions! A free 7-part course, ?How To Pass The CCNA?, is also available, and you can attend an in-person or online CCNA boot camp with The Bryant Advantage!

Cisco CCNP / BCMSN Exam Tutorial: Dynamic VLANs and VMPS

Knowledge of Dynamic VLANs and VMPS is important in your efforts to pass the BCMSN exam and earn your CCNP, and it's also a great skill to have for your networking career.

As a CCNA and CCNP candidate, you know how and why to configure static VLANs. Static VLANs can be a powerful tool for reducing unnecessary broadcast and multicast traffic, but if hosts are moved from one switch port to another, you've got to make those changes manually on the switch. With Dynamic VLANs, the changes are made - how else? - dynamically.

The actual configuration of dynamic VLANs is out of the scope of the BCMSN exam, but as a CCNP candidate you need to know the basics of VMPS - a VLAN Membership Policy Server.

Using VMPS results in port VLAN membership changes being performed dynamically, because the port's VLAN membership is decided by the source MAC address of the device connected to that port. (Yet another reason that the first value a switch looks at on an incoming frame is the source MAC address.)

In my home lab network, I've got a host connected to switch port fast0/1 that resides in VLAN 12. What if we had to move Host 1's connection to the switch to port 0/6? With static VLANs, we'd have to connect to the switch, configure the port as an access port, and then place the port into VLAN 12. With VMPS, the only thing we'd have to do is reconnect the cable to port 0/6, and the VMPS would dynamically place that port into VLAN 12.

I urge you to do additional reading regarding VMPS. Use your favorite search engine for the term configuring vmps and you'll quickly find some great official Cisco documentation on this topic.

To review, the VLAN membership of a host is decided by one of two factors. With static VLANs, the host's VLAN membership is the VLAN to which its switch port has been assigned. With dynamic VLANs, it is dependent upon the host's MAC address.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNP with The Bryant Advantage!

Cisco CCNA/CCNP Home Lab Setup: How To Configure Reverse Telnet

Occasionally, during your CCNA and CCNP studies, you'll run into a term that just doesn't quite make sense to you. (Okay, more than occasionally!) One such term is "reverse telnet". As a Cisco certification candidate, you know that telnet is simply a protocol that allows you to remotely connect to a networking device such as a router or switch. But what is "reverse telnet", and why is it so important to a Cisco CCNA / CCNP home lab setup?

Where a telnet session is started by a remote user who wants to remotely control a router or switch, a reverse telnet session is started when the host device itself imitates the telnet session.

In a CCNA / CCNP home lab, reverse telnet is configured and used on the access server. The access server isn't a white box server like most of us are used to; an access server is a Cisco router that allows you to connect to multiple routers and switches with one session without having to move a rollover cable from device to device.

Your access server will use an octal cable to connect to the other routers and switches in your home lab. The octal cable has one large serial connector that will connect to the access server, and eight rj-45 connectors that will connect to your other home lab devices. Your access server then needs an IP Host table in order to perform reverse telnet.

An IP Host table is easy to put together (and you better know how to write one to pass the CCNA!). The IP Host table is used for local name resolution, taking the place of a DNS server. A typical access server IP Host table looks like this:

ip host FRS 2007 100.1.1.1

ip host R3 2003 100.1.1.1

ip host R1 2001 100.1.1.1

ip host R2 2002 100.1.1.1

ip host R4 2004 100.1.1.1

ip host R5 2005 100.1.1.1

ip host SW1 2006 100.1.1.1

interface Loopback0

ip address 100.1.1.1 255.255.255.255

no ip directed-broadcast

This configuration will allow you to use your access server to connect to five routers, a frame relay switch, and a switch without ever moving a cable. When you type "R1" at the console line, for example, you'll be connected to R1 via reverse telnet. If you have a smaller lab, an access server is still a real timesaver and an excellent investment. And by getting a static IP address to put on your access server, you can even connect to your home lab from remote locations!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com ), home of free CCNA and CCNP tutorials, and The Ultimate CCNA and CCNP Study Packages. For a copy of his FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies!