Cisco Router/Switch CLI vs. Network Topology

---

Hello. First off, I love this site! Thank you to the creators and all of the Edutainers who contribute to this fantastic resource! I've been working on 200-301 and CCNA in general, but I have couple of questions that can't seem to be answered with a general Google search. First, if I want to draw a network topology and identify the ingress and egress interfaces of the switch(es) and router(s), how can I identify those in the router and switch configurations in the CLI? Second, how can I get the "big picture" of what the CCNA wants us to grasp? It seems as if the exam objectives are pieced together and not in an organized fashion. I'm also trying to align the 200-301 certification with what a switch/router administrator would perform in the real world. Thanks for the advice in advance!

@Antwyon-Givens said in Cisco Router/Switch CLI vs. Network Topology:

First, if I want to draw a network topology and identify the ingress and egress interfaces of the switch(es) and router(s), how can I identify those in the router and switch configurations in the CLI?

So from the CLI, you can issue a description command, from either router or switch for example:

R1#config t
R1(config)#interface fa0/0
R1(config-if)#description ingress from WAN1

Second, how can I get the "big picture" of what the CCNA wants us to grasp? It seems as if the exam objectives are pieced together and not in an organized fashion. I'm also trying to align the 200-301 certification with what a switch/router administrator would perform in the real world. Thanks for the advice in advance!

You should read the description of what the exam is testing for from Cisco's site on the exam matters at hand: https://learningnetwork.cisco.com/s/ccna-exam-topics This would be the definitive nature of what the CCNA wants to test you on.

Thanks for being a member!

@Ronnie-Wong Thanks for the information Ronnie. How can I find out if, let's say, fa0/0 is the entry or exit interface of switch?

@Antwyon-Givens,

This is where, I'm not sure if I'm understanding your question. A switchport itself can be both. Switchports are not exclusively entry or exit interfaces. Regardless of networking devices...for the most part can transmit (tx) as well as receive (rx). This would be true if your talking about switches, routers or even firewalls.

Now the closest concept from your original post is that I think you're confusing a switch with firewall. Firewall ports can both tx and rx but they are designed as outside (ingress-traffic on the side going into the firewall to the LAN) or inside (egress-traffice from inside leaving the LAN to the outside)

You may have to provide a context. So let me ask what is it that you are trying to accomplish?

My setup is as follows: I have 2 switches connected to a router. I also have systems with their own switch that connects to my switches. I'm trying to create a network map so it can help me troubleshoot problems in the future. In the CLI, how can I find the interface where workstations connect to the switch and where the switch(es) connect to the router?

@Antwyon-Givens,

The easiest option from the Cisco CLI:

show mac address-table: this command will show you the mac address of the devices connected to the switch. All you have to do is find the mac address of the devices.

I'm trying to track how a packet travels from the workstation through the switch, to the router, and out. I'm trying to find which IP address coincides with which interface? How can I find that?

@Antwyon-Givens said in Cisco Router/Switch CLI vs. Network Topology:

I'm trying to track how a packet travels from the workstation through the switch, to the router, and out. I'm trying to find which IP address coincides with which interface? How can I find that?

I'm still missing some info to help. on how a packet travels from workstation through a switch. if the cable is directly connected from the workstation to the switch, that is HOW it does it -- via the cable. I'm sure I'm not answering correctly because I'm not understanding something you writing. Please provide more if that isn't the answer.

To find the interface to match to the IP... You can do what I mentioned before, find the mac address to that point. Then you can go to those devices and find the IP address on that device.

Maybe a diagram will help with this scenario. How do I find the IP address for the interfaces with the '?' marks in the diagram via CLI?

@Antwyon-Givens,

On the router0, Show IP interface brief

On the switches, you will not see IP addresses on the switchport interfaces unless you've configured them to be routed ports.

@Ronnie-Wong If the switches are unable to be accessed, how will I know where the switches are connected to the router?

@Antwyon-Givens,
if CDP is enabled, on the router you can run a show cdp neighbors