Troubleshooting a network

MilanoChris said:
The academy is a very slow way of learning, designed for college students learning for CCNA in semester. You can teach it to yourself in a few weeks of hard study if you have a networking background or understand the fundamentals.

Get hold of Jeremy's CCNA (ICND 1 and ICND 2) nuggets, much faster and he explains everything so much better.

ICDN 1 is CCENT.
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Yeah, it is slow! My teacher was telling me she did it in 2 weeks. We've been doing this since September, most of the class hasn't even done Discovery 1. I'm trying to get through Discovery 2 before June, should be done though I have lots of other stuff to do!
Figured I will just be doing it all outside of college so if I can do ICDN1 in college then I just have to do ICDN2 outside (or however it works out)

Will take a look at that, I've found the Cisco academy content to be decent. Though a lot of it seems common sense: speaking politely etc.
 
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MilanoChris said:
en
conf t
network 192.168.4.0
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You're missing a step - you have to tell it which routing process to use - RIP / EIGRP / OSPF etc
In this case however, it doesn't matter as the SALES ISR is not running a dynamic routing process - so its a mute point.


I've had a look and there isn't actually anything wrong with this setup., everything actually operates as expected.

Explanation:
From R2, it can ping 192.168.3.1 (it's local interface) indicating that it is indeed up but it cannot ping 192.168.3.2 (SALES ISR) so this indicates to me, some kind of problem as you should be able to ping over a locally connected link -which is "up" - so I'll try from the other side:

As the SALES ISR is a GUI based device, we cannot run ping tests from it directly, so a wireless laptop is the next best thing.
PC's in the 4.0 network are able to ping 192.168.4.1 (their DFGW - SALES ISR LAN), 192.168.3.2 (SALES ISR WAN Interface) and 192.168.3.1 (R2's WAN Interface)
This indicates some kind of restriction on SALES ISR, looking at the type of device, that would suggest that the SALES ISR is a NAT device, essentially you've connected the WAN port to the network (192.168.3.0) and the LAN side is 4.0. so it's inbuilt security is kicking in.

Proving it:
ok, from one of the laptops (doesn't matter which) open a command prompt and type "ping -t 192.168.3.1" then hit enter
This starts up an content ping - click the magnifying glass (inspect) and then click on the SALES ISR, from the menu, click "NAT Table" you will see that the laptop (inside local) is being translated to 192.168.3.2 (Inside global) to further prove the translation, stop the ping from the laptop and pick another, then re-run the same test - you will see that the "Inside local" address will change, but the "Inside global" does not.

Oli - try not to use the "config" tab on the packet tracer too much - use the CLI tab, this way you will learn basic commands like "en" (enable) and "conf t" (configure terminal) you can shorten them down to an extent. If you do configure via the config tab, make sure you look at the equivalent IOS commands section at the base as this show you what you would need to type in to achieve it on a real bit of tin. It's important to know how to interpret a Show running-config (show run) or other show commands as well as being able to type in real-world commands as these are essential :)

Hope that helps!
 
Just had a quick look, I don't understand what's going on lol, I can't even ping the Linksys router from the CLI of Router 2, and I'm sure I could before...
 
Chief Wiggum said:
You're missing a step - you have to tell it which routing process to use - RIP / EIGRP / OSPF etc
Click to expand...
Yes I know this, but I only had a quick look. I assumed falsely from the replies that RIP was running on the Linsys router, but now I see it's not so it's a pointless suggested lol.

As per yourself, I can't see anything wrong.
 
Thanks Chief Wiggum. Read that a few times and think I've got my head around it... Though not sure what the heck I'm going to write for "run appropiate tests and identify and list problems you discover. Correct them and test the network again, produce a report explaining everything.." Because from what we've done at this low level if x can ping y, y should be able to ping x. Which isn't possible on here then.

As mentioned it seems like the whole configuring devices and the CLI, IOS etc is after I pass this subnetting chapter so will learn then and try and do as much of that. Might as well ask my teacher about the 'problem' as well, see what he says!

Now for this! http://i.imgur.com/xyYpS.jpg Which at first looks more annoying then the troubleshooting :p

Thanks again for all your help =)
 
"low level if x can ping y, y should be able to ping x".

Unless NAT overload is in place.

If you've used the WAN port of a device, it'll use NAT Overload to convert addresses.

For example your home network. If you connect to the internet, your local address (e.g. 192.168.0.1) is mapped to your outside local address (which your ISP gives you 87.14.12.3) and a port. So replying devices would use 87.14.12.3:5555 to hit your inside computer.

This means when you ping 8.8.8.8 your router creates a reply address for 8.8.8.8 to use. 8.8.8.8 would reply to your ISP given address 87.14.12.3:5555 which the router would spot and sent on to your local computer; the ping would work.

In your case, it would appear that's working as suggested... however; if 8.8.8.8 were to ping your address of 192.168.0.1 it would obviously fail as NAT won't work unless the connection is initialised from the inside.

I apologise if this is long winded or makes little sense, one has been on the wine.
 
MilanoChris said:
en
conf t
network 192.168.4.0
Click to expand...
I now know what that means ;) Just gone through the configuring a router and switch section on Cisco acadamy... it was LONG, double the length at least of the previous longest chapter.

Lots of things I understand and some things I don't.... going to have reading through it again :(
 
Yeah, I still need to go through the acadamy for college. Ideally wanting to finish Discovery 2 but as mentioned that chapter took me hours to read..

Got CBT nuggets, good stuff :D Explains everything well and its not boring.

So trying to watch the videos which correspond to whatever I'm doing on the acadamy. But also read through the chapters because might be things I need to know what isn't mentioned in the videos.
 
So I'm doing more P tracer exercises and feeling like a idiot. I've gone through my academy tests about setting up routers and switches and routing protocols and I can't do this -.-

Anyway. 3 floors in a building, a switch per floor and 1 floor has 2. 4 laptops need to connect as well. 22 computers will be connected per switch.
I need to setup the network, give laptop dynamic IPs (done) and static ones to the desktops (done). They can all ping each other fine. The private network is 192.168.1.0

Problem:
ISP has provided the IP address of 210.155.221.16 /24. So I go into the GUI of the wireless router (WRT300N) and am failing on setting up the static IP for the WAN interface. Just need to be able to ping it.

Internet IP: 210.155.221.16 (as assigned by ISP)
Subnet: 255.255.255.0
Default Gateway: 210.155.221.x? I would've thought the IP address would be the same as the gateway for a router.. no?

I feel embarrassed :p

http://dl.dropbox.com/u/67409120/design.pkt
 
Hi Oli,

Just sat down after finding a few mins to look at this (running PTracer on a VM)...
OK - you don't need to set a DFGW for the Internet interface on the router for this to work. I note that you have an ISP router with no config on it in the LAB, and this is not connected to your site router.
If you connect a x-over cable from your site router to one of the interfaces on the ISP router (the lights will be red) then no shut the connected interface on the ISP router (turn it on if you CBA to do it via the CLI) you'll see the link go green, and you'll be able to ping the internet address of the site router. Why is this? Read on:

Explanation:
A router is there to connect 2 or more networks, in it's most basic form it will route between "connected" networks with minimal configuration. "Connected" basically means configured on the router as an interface. However, the router software is smart enough to know that if the interface is down (not connected or shut) then the network, even though defined as an interface is no-longer "connected" i.e. it's not there any more so it's not reachable. This is why when you try to ping the internet address the router returns "destination unreachable" even though it's actually configured on the same router.
As soon as you bring that interface "UP" it's suddenly connected, so it can be entered into the routing table.

The best way to see this in action is to do the following:
Open a new lab and drop in a CLI (1800 or similar) router with a switch.
on the router configure one interface with 192.168.0.1 and a /24 mask and the other with 192.168.1.1 and a /24 mask
from the cli, make sure you're at the enable prompt and type:
show ip route

you should see:
Code: 
Router#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

Router#
Now, bring up one of the interfaces and connect it to the switch, once it goes green run the "show ip route" command again - what has changed?
Repeat for the other interface and compare.


Hope that helps :)
 
Oh right! Yes I had put the ISP router there but sort of just left it! Makes perfect sense about the interface being down. Simple solution then :)
Will do it when I'm back at my desk.

Thanks a lot once again =)
 
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