Spuluka, thanks for you response! I really appreciate it.
The situation with the modem and firewall and multiple vlans was just a reference to a situation that I wanted to try to avoid in this current situation. If fact, I think you were the person who originally explained the same thing you just said which helped me out a lot back then. Thanks AGAIN!
This situation now is just a basic one-vlan network running through the ex2000-c switch using vlan-400 and a l3-interface config for that vlan. The questions that are important to me have to do with two things:
-pinging the loopback in the switch
-making the switch do the routing instead of the cable modem so that this might make it possible to ping the loopback in the switch. The reason I want to be able to ping the loopback is because I am learning to run SNMP management software using OpenNMS and this server needs direct access to the switch.
Here are my specific questions. I really would like to better upderstand how the loopback - lo0 - interacts with the inner workings of the switch and its engines.
Could you give me some idea of the commands I would need to use to make the ex2200-c the core router (the switch is doing the layer-3 routing for the vlan-400) and still have the cients get to the Internet through the switch to the cable modem? I kind of thought that what we were already doing this when we added the
set vlans vlan-400 l3-interface vlan.400
But that shows you right there the depth of my understanding of routing, and especially how to implement it: limited, but trying to make headway.
HERE IS MY MAIN CONFUSION: Smicker had been very helpful in suggesting that one solution would be to use the switch as my core router. And I had asked:
What is really meant by the phrase 'core router' beyond using the l3-interface command? Since layer 3 in the OSI is where ip addressing comes into play (beyond layer 2 MAC adressing within one broadcast domain) I kind of thought that when we add this command, 'l3-interface', we are giving the ability of that vlan to be routing. And you stated that the loopback was a virtual layer 3 interface. So why can't the layer 3 vlan-400 route to the layer 3 loopback?
This is were I thought that adding some kind of static route in the routing-table (a layer 3 map) would allow traffic destined for the loopback to be able to get to it and get back. But when you reminded me that directly connected addresses don't need to be explicity added to the table, I got confused. I understand the concept, but is the loopback directly connected? And if it is, then why can't vlan-400 traffic automatically find it?
So why would the vlan-400 not be able to route to the lo0 inside the switch at that point? I would really think it would be awsome if you could really explain this to me! I have studied the differenct engines inside the switch, the forwarding engine and the routing engine, but I just can't really get how you utilize them in the practical world. And how to make one of the engines be able to connect to the loopback which, as I think you said, is on layer 3 itself, but only virtually (does virutally require some special connecting statement to get l3-interface vlan-400 to communicate with the loopback virtual layer 3 interface?). I think answering this could be very valuable for many people because I think that this represents a lot of confusion and a common transifional understanding that I've seen reflected in many quesitons I have seen people asking. There is some internal logic here between forwarding, routing and the inner workings of Juniper devices that seem hidden to the general population of techies.
Also, I thought that core just kind of meant the position a device had in the scheme of things. I kind of get that the cable modem is now doing the routing and that you are suggesting that I have the switch take over this role.
THANKS MUCH,
Robin Hood