WAN Links

PPP123

Hi all

I've just started VLSM. Although I have figured out how to complete various networks accordingly using VLSM I'm struggling to understand why you assign 2 hosts to each WAN link?

I can't find anywhere that tells you why?

Maybe it's horribly simple and I'm overthinking/overlooking something

clarson

Well, most wan links use a point to point technology. So, you have one host connected to one host. All your network needs is two host addresses. And, any additional host addresses are just wasted.

PPP123

In the example I was looking at I have 4 routers connected to each other, 4 links and 8 hosts in total. Why not just 4 hosts, 1 for each router?

clarson

i guess you could do it that way. But, in the real world, routers connect networks. and each network requires only one router host address. (ok more for fhrp redundency, but we aren't there yet).
Of course, you could connect several routers together on a single network. But, then you create a single point of failure for several networks. That isn't good network design.

This relates to "how to properly design a network". Which is covered in the "Design" series of certifications, ccda, ccdp, etc. You will get into design topics with the ccnp also. So, you can look into those material to learn more. Something like, Enterprise Campus 3.0 Architecture: Overview and Framework - Cisco

MAC_Addy

A majority of the time when I've seen this is when you order a WAN circuit at a company - the internet provider will assign a /29. One for their equipment, and one for yours.

DCD

MAC_Addy wrote: »

A majority of the time when I've seen this is when you order a WAN circuit at a company - the internet provider will assign a /29. One for their equipment, and one for yours.

Don't you mean /30

PPP123

Thanks for the input guys.

A paragraph sourced from online really hit the nail on head:-

Each link between adjacent routers is a separate IP subset, and so each router needs to have an IP address assigned to it. This IP address is used by the routing protocol for adjacency establishment, source IP of routing advertisements, next-hop information for routes, etc.

MAC_Addy

DCD wrote: »

Don't you mean /30

You got me, yes. Though typically with AT&T (in my experience) they have assigned a /29.

DCD

MAC_Addy wrote: »

You got me, yes. Though typically with AT&T (in my experience) they have assigned a /29.

Not trying to get you MAC_Addy just lending a helping hand. I usually work with Level3 and Masergy and XO Communication and they normally do /30. We were doing a network upgrade and needed a /29 for some of the site and one of the companies kept giving a /30 LOL.