Routers
| VLAN | Default Subnet(s) |
|---|---|
| 7001 | 172.21.1.0/29 |
| N/A | 10.100.0.0/16 |
Wait two segments? And one doesn’t have a VLAN?
Lets talk about the first subnet first, 172.21.1.0/29. Why is it numbered so differently than the other networks? Because it is the network segment that the two routers are going to form an adjacency in. No device other than these two routers needs to talk to these IPs. For monitoring purposes, NEMS is also allowed to ping these. For example, in our scheme, consider the following:
| Router | Interface | Address |
|---|---|---|
| Edge | eth1 | 172.21.1.1/29 |
| Internal | igc0/eth0 | 172.21.1.2/29 |
| Edge Loopback | lo0 | 10.100.1.0/32 |
| Internal Loopback | lo1 | 10.100.2.0/32 |
The first two entries are the interfaces on each router that will be active in the OSPF process. Don’t sweat this too much, just be aware that they send OSPF hellos to eachother from those interfaces, and listen for Link State Advertisements (LSAs).
The second two entries are the loopback interfaces for each router. This is going to be used as the Router ID for the OSPF process. Note that they are /32 addresses because they are purely routed interfaces, they do not have a Layer 2 component. Don’t sweat this either. You don’t have to understand OSPF to follow the instructions later.