what is considered a layer 4 router

clarson

would a layer 4 router have to have special hardware to be considered a layer 4 router or is that just something that is implemented in the ios software. It would seem that layer 4 things are like nat and load balancing. Would something like a 2800 be considered a layer 4 router?

EdTheLad

I imagine a layer 4 router means cef is using layer 4 info for forwarding decisions. I would presume a new asic would be required to take into account the additional info. What hw is supported? good luck reading product array specs .

tuleeoh

Never heard the term L4 router before...L2 deals with forwarding MAC addresses (Layer 2 addresses) and L3 deals with routing IP Packets (Layer 3 addresses). There is nothing to route or forward at the layer 4 - the transport layer.

Jon_Cisco

I have never heard of a layer 4 router so I goggled it. This is what I found but I have no idea how accurate it is.


TITLE
Layer 4 Router

PUB. DATE
March 2007

SOURCE
Network Dictionary;2007, p281

SOURCE TYPE
Book

DOC. TYPE
Reference Entry

ABSTRACT
A definition of the term "Layer 4 Router" is presented. This refers to a network router that uses the Transport Layer information in making decisions on where to send the packets. Unlike a layer 3 network device, layer 4 router sends incoming packets to one or more machines that are hidden behind a single Internet Protocol address.

theodoxa

The ^^^ sounds like PAT/NAT Overload. I do remember reading about Layer 4 and Layer 7 Switches in my SWITCH studies, which can make decisions based on Layer 4 (TCP/UDP Ports) and/or Layer 7 (Applications).

EdTheLad

It's a very simple concept, the layer 4 info can be used to build the cef table for more granular cef switching. People like to make up new expressions like layer 4 router etc etc for marketing.

Fulcrum45

Correct me if I'm wrong but don't all basic home routers NAT and almost all certainly PAT? Just a fancy new expression as previously mentioned it sounds like.

TechGuru80

Funny how that article says packets...layer 4 has segments not packets...

santaowns

Sounds a lot like what we call VIPs at work. We use them for load balancing.

kianm

Ok this is new to my ears and would like to see credible information about it, otherwise