How does routing work?

Roguetadhg

So what is routing anyways?

Yeah, it's a review for some, and might be a new concept for others. Either way, it's important and a generic

sratakhin

Let me google that for you

P.S. I see that you have N+ and CCNA. Is this topic a joke or what?

NetworkVeteran

sratakhin wrote:

P.S. I see that you have N+ and CCNA. Is this topic a joke or what?

I have a bit more than that, and I don't see it as a trivial question.

Your Google turned up--

sratakhin wrote:

Defeat and cause to retreat in disorder: "in a matter of minutes the attackers were routed".
Cut a groove, or any pattern not extending to the edges, in (a wooden or metal surface).
Send or direct along a specified course.

Let's see. My guess, without looking it up--

The process of finding a route across a network, akin to finding a path through a weighted graph.

A Router is a L3 device, but Routing doesn't necessarily imply L3.

E.g., Token Ring performs Source Routing at L2.

Ltat42a

Check out this video -
Warriors of the Net clips

Somnipotent

Routing... hmmm... well, think of a letter addressed to your Dear Aunt Sally.

• You write your letter (data) and put in an envelope (packet encapsulation)
• You put that letter in a box with a specific HOUSE number (Source MAC address) and ZIP code (Source IP Address) and your Aunt Sally's address (Destination MAC and IP addresses)
• You put it in a box and the postmaster (Physical Link) takes your letter to the Post Office (Router) The PO checks out the ZIP code (they don't care about the street address, just which post office to forward it to) and send it to the destination PO (route lookup and forwarding)
• In the process of getting to the destination PO, it goes through several POs to get to the final PO. If there's some kinda storm or traffic, the letter gets rerouted, depending on the conditions, if it's based on how big of a road it should take or the shortest route (Routing metrics).
• When it gets to the last PO, the Postermaster looks at the ZIP code to make sure it's in the right office, then sends it to the postman's bin whose route it's on. He looks up the house number for Aunt Sally and delivers it to her box.
• Aunt Sally gets the letter (she knows it's hers because it's addressed to her), opens it, and reads it.
• She sends her response and it goes back through the same hoops.

That's how I described it to my technology deficient wife.

Roguetadhg

It doesn't hurt to keep the basics recycled through that noggin. Keeps it fresh!

fiftyo

"As a packet of a connectionless network layer protocol travels from one router to the next, each router makes an independent forwarding decision for that packet. That is, each router analyzes the packet's header, and each router runs a network layer routing algorithm. Each router independently chooses a next hop for the packet, based on its analysis of the packet's header and the results of running the routing algorithm."RFC 3031 - Multiprotocol Label Switching ArchitectureUnder section 2.1 Overview