- Blue, 1500 points or more
Folks, I need some clarification on this.
I have a question regarding architecture and a "simple" implementation.
here is the set up:
I have a router and its fa0/0 interface is connected to a catOS L3 switch's 9/1 port.
Here are the pertinent configs:
interface vlan 21
ip address 10.27.21.3 255.255.255.0
set vlan 21 9/1
SO, PORT 9/1 IS IN VLAN 21.
ip address 10.27.21.4 255.255.255.0
OK, so whats the big deal, right?
I want to know if this ethernet connection between the L3 switch and the router is considered a layer 2 or layer 3 connection.
My answer would be that it is a layer 3, routed connection because port 9/1 was placed in vlan 21 and vlan 21's layer 3 (SVI) interface was configured on the switch's MSFC. Right? So, its like creating a point-to-point link in which port 9/1 would have the host address of .3 (vlan inerface address on the MSFC) and the router would be .4 In fact, we could have used a /30 subnet mask instead of the /24.
Here is where I need clarification: Lets say I DID use a /24, instead of the /30, and then I added 3 more ports to vlan 21 and connected those 3 ports -- say, 9/2, 9/3 and 9/4 -- to 3 other routers. Now, in the previous example, we said that port 9/1 would take on the IP address of .3, but now I have added 3 more ports to that vlan and have connected them to 3 different routers. So, what IP addresses would those ports assume??? After all, I only have 1 vlan 21 interface configured on the MSFC (as well I should), so what about ports 9/2-3-and 4? What IP addresses do they assume??
Or could it be that I am looking at it the wrong way? I mean, yes, the links would be considered layer 3, ethernet links between the L3 switch and all the routers, but the switch ports (9/1-4) should not be viewed as having "adopted" any IP address. Does that make any sense? If so, how SHOULD I be looking at those port's IP characteristics?
Thank you for your help