Benefits of Layer 3

[mmcgurty]

I've got what I hope is an interesting question. What are the benefits to a Layer 3 switch being installed in a prodominately Layer 2 switched network? What will I gain by doing say a Cisco 3750 where I used to do a "router on a stick" approach? What would I gain security feature wise?

One thing I keep hearing is that is reduces broadcasts and network chatter? How does one go about determining that they have too many broadcasts or network chatter? What security features can be implemented that I cannot already do with a Cisco 2924XL or 2950?

Any and all advice would be appreciated. Thanks!

 

[jneiberger]

If you already have L2 switches plus a router then you really don't gain much by doing away with your router and using a 3750 instead. In fact, it could be argued that you're actually losing functionality depending on the router you've got, although I'd imagine it must be an older router if you're thinking of replacing it with a 3750.

A layer 3 switch won't do anything for broadcasts and network "chatter" that a router doesn't already do. A layer 3 switch is simply a L2 switch with some routing functionality thrown into the same chassis. There's nothing magical about it.

 

[vipergg]

While it is basically the same setup with the routing function all in one box I think you will find most of newer layer3 switches to be considerably faster than say a router on a stick specially if you using a lower end router like 1600, or a 2600 box .

 

[Kapfel]

- you should gain speed due to the 3750 performing CEF which uses two forwarding tables, FIB (reformatted route table as well as host routes /32 mask) and Adjanceny (arp table) to forward packets at hardware speeds.

- Not sure/don't see how you would gain addtional security.

- only way i see you reducing the chatter/broadcasts is by reducing the amounts of arps due to the adjanceny table containing the mac addresses of the nodes that can be reached in a single layer 2 hop.

 

[ADB100]

I would add that moving to a Layer-3 environment removes the complexities of engineering STP that is a pain (and is rarely done anyway) in a Layer-2 environment. A layer-2 network is inherantly difficult to troubleshoot due to the plug-and-pray attitude people take when deploying layer-2 networks.

Andy

 

[vlf]

One more thing. Your router on a stick is going to be limited by the bandwidth of the stick. Having L3 in your switch can increase the performance because you're using the backplane, which is generally more effecient.