Day 12: One Area Per Site

Twenty-one months at Halverton.
Next quarter the company opens two depots, Austin and Omaha, and both hang off R-WAN1.

The WAN is still one OSPF area. Every router holds the routes of every site.

Figure 1 – Every site in area 0

Why It Hurts

Last Thursday, a link at Reno flapped for four minutes.
Every router in the company recomputed its routes, Tulsa included.

In one area, every change reaches every router.
Tulsa does not need the routes of Reno. It sends everything to R-WAN1.

Sarah:

"Split the WAN into areas before Austin and Omaha come online. One area per site."

One OSPF area per site.
The area number is the second octet of the site. The Tulsa docks are 10.31.30.0/24, so Tulsa is area 31.

Table 1 – One area per site

HQ keeps its own subnets in area 0, and so does the link between R-HQ1 and R-WAN1.
The link between R-WAN1 and a site goes in the area of that site.
R-WAN1 sits in all four areas. It is the ABR.

The three site areas are stub.
A stub area does not receive the routes of the other sites. Its router gets a default route to R-WAN1 instead.

Figure 2 – Four areas, one ABR

Lab Instructions

You have the console on R-WAN1, R-TULSA1, R-DEN1, R-RENO1 and on the Tulsa dock PC.
The Denver dock PC is 10.52.30.10.

Everything pings when you start.
It still has to ping when you finish.

• Put each site in its own area

• Make the three site areas stub

• From the Tulsa dock PC, ping the Denver dock PC

• Save the configuration on the four routers

Finish the lab, then type the flag below.

Austin and Omaha come online in April, in area 33 and area 47.

Sarah stops by your desk the week after.

"A Network Engineer position opens in June. You should apply. Have a look at the ENCOR blueprint first."

You open it that weekend.