Do I really need PoE switches

itdaddy

hey guys I am building my voip lab do i really need PoE switches
if the Ip phones have power bricks and what really does a L3 switch
do in regards to Ip phones that a 2950 cant do? cant a 2959 do Qos
so wont it work in my setup? yeah iw ould like a poe switch but since the ip phone have power blocks what does a L3 Poe swicth give me that 2950 doesnt?

azaghul

I guess PoE switches fall into the "nice to have" category. But as you already have power bricks for your 7900 phones, you can get by without them.

APA

depends on how much cash you have and whether you think of the bigger picture in terms of perhaps needing 3560 later on in your studies?

I know there are quite a few difference in terms of comparing a 2950 to a 3560.... (can't remember them all....)

But if you're purely talking about PoE.... then no you don't need the 3560 if you have power bricks.....

itdaddy

thanks apa yeah I just dont wnat to spend too much more if I really dont need them for anything yet unless L3 stuff?

APA I like this guys explain on why Dan it I have to get one

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2950 vs 3560 or 3550 L3 switch

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Basically a layer 2 switch operates utilizing Mac addresses in it's caching table to quickly pass information from port to port. A layer 3 switch utilizes IP addresses to do the same.
While the previous explanation is the "What", for folks in networking the following "How" is far more interesting.
Essentially, A layer 2 switch is essentially a multiport bridge. A layer 2 switch will learn about MAC addresses connected to each port and passes frames marked for those ports. It also knows that if a frame is sent out a port but is looking for the MAC address of the port it is connected to and drop that frame. Whereas a single CPU Bridge runs in serial, todays hardware based switches run in parallel, translating to extremly fast switching.
Layer 3 switching is a hybrid, as one can imagine, of a router and a switch. There are different types of layer 3 switching, route caching andtopology-based. In route caching the switch required both a Route Processor (RP) and a Switch Engine (SE). The RP must listen to the first packet to determine the destination. At that point the Switch Engine makes a shortcut entry in the caching table for the rest of the packets to follow. Due to advancement in processing power and drastic reductions in the cost of memory, today's higher end layer 3 switches implement a topology-based switching which builds a lookup table and and poputlates it with the entire network's topology. The database is held in hardware and is referenced there to maintain high throughput. It utilizes the longest address match as the layer 3 destination. Now when and why would one use a l2 vs l3 vs a router? Simply put, a router will generally sit at the gateway between a private and a public network. A router can perform NAT whereas an l3 switch cannot (imagine a switch that had the topology entries for the ENTIRE Internet!!). In a small very flat network (meaning only one private network range for the whole site) a L2 switch to connect all the servers and clients to the internet is probably going to suffice. Larger networks, or those with the need to contain broadcast traffic or those utilizing VOIP, a multi network approach utilizing VLANs is appropriate, and when one is utilizing VLANs, L3 switches are a natural fit. While a router on a stick scenario can work, it can quickly overtax a router if there is any significant intervlan traffic since the router must make complicated routing decisions for every packet that it recieves.

mikej412

No, you don't need PoE switches. There was a previous thread about this.

Power bricks are cheaper -- as long as you don't get the cheap $6 ones that burst into flames and burn down your house.

You'd may want a layer 3 switch for the QoS exam -- since QoS features vary by switch. I'm not sure if the QoS exam has been updated for the 3560 (or 3750) yet, so the 3550 probably would still work (along with a 2950 or 2960).

If you check out and page through the Odom QoS book you should be able get an idea about whether you need to buy one -- or could just get by with a couple of rack rental sessions. Depends on how comfortable you feel just memorizing the stuff for the exam vs learning it hands on and being better able to apply it "on the job" later.

mikej412

mikej412 wrote: »

There was a previous thread about this.

Okay -- it was brought up in a previous thread that wasn't specifically about PoE Switches....

http://www.techexams.net/forums/ccvp/27959-ccvp-home-lab.html#post187912

dtlokee wrote: »

You really don't need a PoE switch at all, the power bricks work just fine.

mikej412 wrote: »

From a cost viewpoint, that is cheaper

I already had the 3550 PWR when I did my CCVP, so I didn't worry about the power bricks.... but 3 of the phones I bought on eBay came with them. One brick seems like a Cisco Original. A 2nd brick seems like a solid 3rd party "mystery brick."

The 3rd brick was a smaller form factor and marked similar to the "original" and seemed fine when I got it, but it just fell apart on its own a few months later (with no use) when I was moving it to another storage spot. I think it was a "knock off" someone had bought for use in their lab -- and once it was open, it seemed very shoddy and low quality.

If you go the power brick route to save some money, try to avoid the cheapest ones -- or at least make sure your smoke detectors work and your house insurance is paid up.

itdaddy

thanks mikej.
yeah I read some of that but wasnt sure if things had changed since I am alittle behind the powercurve here. thankyou for your help and harsh-firm but funny-serious direct humor..


I appreciate your help really...

APA

BTW - itdaddy.... where on earth did you get that explanation from?

The guys only explains the blatant obvious.... L2 switch only handle L2 functions... L3 switch can handle L3 functions.

A L3 switch does not only forward packets based on IP address...... if the L3 switch needs to switch it will switch between ports just like the L2 switch based on mac-addresses learnt via each port.... If the L3 switch needs to route then it has this added functionality to route at L3 which obvious the L2 switch does.

I'd suggest hoping on Cisco.com and taking a look at specs..... as I got a 3560 for my home lab purely for switch QoS requirements as the 3560 is quite feature rich in that aspect.