Linksys/D-Link Routers and your Cisco CCNA Lab

We get many CCNA students who ask us how to incorporate their Linksys/D-Link or similar Cable/DSL wireless router into their newly purchased Cisco CCNA lab. Although this can be done, it is not something we suggest.

I will touch on a few reasons we dont really recommend this setup, but I am sure if we really sat down and thought about it we could come up with more.

1) Depending on the model of the home Linksys/D-Link Cable/DSL router that you are talking about, many of them dont support the protocols you will be setting up in your Cisco CCNA home lab. Some of the newer ones will support RIP. But rarely will you see any of these home type routers support any of the advanced protocols such as OSPF, EIGRP and such. A few of them are now also supporting the ability to enter static routes, which is niceand they are improving with each generation but they still are not what you want to base your Cisco CCNA studies on.

2) Most of them come out of the box setup as DHCP servers. Unless you start playing around with those settings, this will conflict with some of the DHCP and other labs you should be doing in your CCNA lab. This generally leads to breaking your home network and then you have your spouse, parents, kits, etc complaining because you took down their Internet connection. The more they complain, the more you stress out and keep figure out the solution as everyone is yelling at you. Just dont do it!

3) Besides the ability to not support all the protocols a real Cisco router willthe Linksys/D-Link Cable/DSL routers will not be able to work seamlessly with many of the advanced security features you will find in a Cisco Router during your CCNA lab studies.

So what we suggest for the new Cisco CCNA student is to keep their home Linksys/D-Link Cable/DSL network separate from their Cisco CCNA lab network. Why besides the items listed above? Well another thing we tend to find is you are learning in the new CCNA lab network. You are going to break things and spend countless hours trying to figure out what you did wrong, how to fix it and what you broke. Many times you will never figure it out and just start over from scratch. Also one thing you will discover with Cisco routing is an issue with one Cisco router will propagate to other routers. For example, when an interface goes down on a router, the route is removed systematically from the route tables of all the routers. Thus routes are recalculated and you will be sent a different way to get to the destination. So long story short, we suggest in the beginning learning stages, keep your home network and CCNA lab network completely separate.

Integrating your home and CCNA networks sounds like a great idea until you totally mess it up, have no idea what you are doing or how to fix it while your spouse, kids, parents, whomever are yelling at you because they cant get to their myspace account.or worse yet, now you cant get your home network back working to the point where you can get to some of your favorite websites or email accounts. So just be patient and progress at a slow steady pace with your CCNA studies. Before you know it you will actually understand how to integrate the two networks from knowledge you gained through your studies and not because someone gave you an example to type in and follow. You will actually be able to sit down and figure it our for yourself. This is a true measure of your comprehension of the Cisco CCNA exam concepts and will provide you with a real life situation where you can test your Cisco CCNA expertise!

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Cisco CCNA Certification – Cisco VTP VLAN Trunking Protocol

(VTP) is a Cisco Layer 2 messaging protocol that manages the addition, deletion, and renaming of VLANs on a network-wide basis. Virtual Local AreaNetwork (VLAN) Trunk Protocol (VTP) reduces administration in a switched network. When you configure a new VLAN on one VTP server, the VLAN is distributed through all switches in the domain. This reduces the need to configure the same VLAN everywhere. VTP is a Cisco-proprietary protocol that is available on most of the Cisco Catalyst Family products. VTP ensures that all switches in the VTP domain are aware of all VLANs. There are occasions, however, when VTP can create unnecessary traffic. All unknown unicasts and broadcasts in a VLAN are flooded over the entire VLAN. All switches in the network receive all broadcasts, even in situations where few users are connected in that VLAN. VTP pruning is a feature used to eliminate (or prune) this unnecessary traffic. By default, all Cisco Catalyst switches are configured to be VTP servers. This is suitable for small-scale networks where the size of the VLAN information is small and easily stored in all switches (in NVRAM). In a large network, a judgment call must be made at some point when the NVRAM storage needed is wasted, because it is duplicated on every switch. At this point, the network administrator should choose a few well-equipped switches and keep them as VTP servers. Everything else participating in VTP can be turned into a client. The number of VTP servers should be chosen so as to provide the degree of redundancy desired in the network.

Modes of OperationServer

In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP servers advertise their VLAN configuration to other switches in the same VTP domain and synchronize their VLAN configuration with other switches based on advertisements received over trunk links. VTP server is the default mode.

Transparent

VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, transparent switches do forward VTP advertisements that they receive out their trunk ports.

Client

VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.

Advertisements Summary Advertisements

When the switch receives a summary advertisement packet, it compares the VTP domainname to its own VTP domain name. If the name is different, the switch simply ignores the packet. If the name is the same, the switch then compares the configuration revision to its own revision. If its own configuration revision is higher or equal, the packet is ignored. If it is lower, an advertisement request is sent.

Subset Advertisements

When you add, delete, or change a VLAN in a switch, the server switch where the changes were made increments the configuration revision and issues a summary advertisement, followed by one or several subset advertisements. A subset advertisement contains a list of VLAN information. If there are several VLANS, more than one subset advertisement may be required in order to advertise them all.

Advertisement Requests

A switch needs a VTP advertisement request in the following situations:

The switch has been reset. The VTP domain name has been changed. The switch has received a VTP summary advertisement with a higher configuration revision than its own. Upon receipt of an advertisement request, a VTP device sends a summary advertisement, followed by one or more subset advertisements.

Configuration To configure an IOS based switch to be a VTP server, issue the following commands: SwitchA# vlan database

SwitchA(vlan)# vtp domain CiscoKits

SwitchA(vlan)# vtp server

SwitchA(vlan)# exit

These commands configure the switch to be a VTP server in the VTP domain CiscoKits. The changes are saved and the revision number is incremented when the exit command is issued. To configure a VTP client, run the following commands:

SwitchB# vlan database

SwitchB(vlan)# vtp domain CiscoKits

SwitchB(vlan)# vtp client

SwitchB(vlan)# exit

To disable VTP, set the vtp mode to transparent as such:

SwitchC# vlan database

SwitchC(vlan)# vtp transparent

SwitchC(vlan)# exit

To monitor the VTP operation and status, use either:

SwitchA# show vtp status

SwitchA# show vtp counters.

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Cisco CCNA Exam – Routed Protocols Vs Routed Protocols

You must know the difference between a “routed” protocol and a “routing” protocol. A routed protocol can be routed by a router, which means that it can be forwarded from one router to another. Examples of a routed protocols are IP, IPX and AppleTalk.

A routed protocol contains the data structure for a packet to be sent outside of its local network segment. This structure is called an addressing scheme. Based on the addressing scheme, you will be able to identify the network to which a host belongs, in addition to identifying that host on that network. All hosts on an internetwork (routers, servers, and workstations) can communicate with each other by using a routable protocol such as IP, IPX or AppleTalk. A routingprotocol is used to communicate routing information between routers. Its purpose is to help routers building and maintain routing tables. Examples of routing protocols are RIP, IGRP, EIGRP and OSPF(there are many others). When a router has built a complete routing table from the various routing protocols it supports, it will be able to most efficiently forward traffic via the best route.

Routed Protocols

As mentioned above, IP, IPX and AppleTalk are three common routed protocols. The exam focuses on IP since that is the predominant protocol used today. So what do you need to know about IP other than that is how all your node to node communication will occur? Make sure you know how to subnet! If you do not know how to create subnet masks to most efficiently meet a desired goal of number of subnets and hosts, you will most definitely fail the exam. Understanding how to subnet will not guarantee that you will pass this exam, but not understanding subnetting will guarantee that you fail! If you have an IP address and its subnet mask, you need to be able to identify the subnet ID of that host, the first and last useable host on that subnet, the subnet broadcast address, in addition to the number of possible subnets and hosts per subnet. If those items do not come easily to you, then you will need to brush up on these concepts. Remember you have roughly a minute per question on the exam. If it takes you more than a minute to figure the above items out, you will not finish the test in the allotted time. In addition, you will need to know how to recognize a subnet mask in its dotted decimal form (255.255.255.248) and by using a bit count (/29). You should also know which bits must be off and on in the first octet for the various classes of IP addresses (Class B would have “10″ in the first two bits).

Routing Protocols

The CCNA objectives only require that you know how to configure RIP and IGRP. However, you do need to know about the three classes of routing protocols (distance vector, link state, and hybrid), and which protocol belongs to which class. RIP and IGRP are distance vector protocols. OSPF is the only link state protocol with which you need to concern yourself at this level, and EIGRP is the only hybrid protocol. Know which protocol has a lower administrative distance (RIP is 120 vs. IGRP is 100), and that static routes have a lower administrative distance if you use the defaults a static router is 1 and a directly connected router is 0. When configuring RIP or IGRP, make sure that you also know how to turn on the attached networks so that they will start sending and receiving routing updates(network xxx.xxx.0.0).

Also remember that IGRP requires the addition of an autonomous system number(AS xx). Be familiar with the metrics RIP and IGRP use in determining the best path through which to route. RIP for IP only uses hops and IGRP uses only Bandwidth and Delay be default but can also be configured to use Bandwidth, Delay, Reliability, Load, and MTU. Remember that “show ip route” displays the contents of all routing protocols in your routing table.