How do the router switch ports relate to the WAN interface

[creeping666]

I have an 877 router with 4 switch ports, all in VLAN 1 and I'm unsure how VLAN 1 relates to the ATM WAN interface.

ie.
Its clear if a router two layer 3 interfaces (ATM or fast ethernet on the WAN side and a fast ethernet on the LAN side) because they are both level 3 and they can both have IP addresses assigned directly to them.
The fast ethernet LAN interface would most likely go to a switch.


But in the 877 the switch ports are only level 2 so they must be in a VLAN, is it best to think of VLAN 1 as a logical layer 3 interface but with all the limitations of layer 2?

Or would you picture the swicth ports (VLAN 1) as separate from the ATM interface and treat as just a switch?

For example. Think of them as separate devices, a switch linked to a router (with one ATM interface) via a ethernet cable.

If you can understand my ramblings that is

Thanks.

 

[burtsbees]

The switchports are layer 2 in and of themselves, but when the vlan is created, the SVI (logical interface) is created, which is layer 3. The fastethernet layer 2 ports are all part of vlan1. The 837 is sort of like this---ethernet1 is the L3 interface, and fa1-fa4 are the L2 interfaces. E1 is not a physical interface---it's the logical interface that the IP address gets attached to. This is like an automatic SVI, but it's not exactly a VLAN in the conventional sense of the word---it acts like one, but that model does not have the functionality to create an actual vlan (interface vlan1, etc.).

Burt

 

[creeping666]

Yea thanks everyone, I did alot of research. Maybe that was part of the problem, the more I read, the more people mixing terms etc (not in this forum) which looked conflicting and made it confusing.