Solved

What went wrong, Alpine 3808 <-> Cisco 3560G.  Cisco hangs.

Posted on 2006-07-13
3
369 Views
Last Modified: 2006-11-18
We have a small flat (non routed) network.  Originally it looked something like this:

internet <-> router <-> firewall <-> ALPINE 3808 switch <-> all our PC & Unix machines

We installed a Cisco 3560G in the network so that all the UNIX boxes can run at Gig network amoung themselves.  
So now internally it is something like this:
  UNIX machines 1000 mb <-> Cisco <-> ALPINE <-> PC & Misc servers 100mb
The Cisco 3560G uplink plugs back into the ALPINE 3808

I hope I've given a good idea of what the network looks like.  Now the problem -
Someone plugged one of the ports of the Cisco 3560G into a port on the ALPINE, regular cat5 cable ... and the Cisco hung.  We had to (unplug it from the Alpine) and reboot it to get that segment of the network back up and running.

What did we do wrong?  What basic networking concept are we missing?
0
Comment
Question by:bjmorse
3 Comments
 
LVL 28

Assisted Solution

by:mikebernhardt
mikebernhardt earned 150 total points
ID: 17103936
Do you mean that someone plugged an additional cable in between the Ciso and the Alpine or an initial connection only? If something was misconfigured you could have created a spanning tree loop if you had 2 connections, which could bury the switch's cpu.
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 150 total points
ID: 17104047
Yep. Sounds like a broadcast storm.

>What did we do wrong?  What basic networking concept are we missing?
Don't create a layer 2 loop unless spanning tree is enabled and properly configured. :-)

-Don
0
 
LVL 12

Accepted Solution

by:
Scotty_cisco earned 200 total points
ID: 17104178
the cisco should have gone into a blocking state if spanning tree worked properly

enter the following command

switch#spanning-tree blocked ports

this will tell you if it blocked or has any blocked ports

also do a show spannin-tree

this will tell you if spanning-tree is even running.

Thanks
Scott
0

Featured Post

Do You Know the 4 Main Threat Actor Types?

Do you know the main threat actor types? Most attackers fall into one of four categories, each with their own favored tactics, techniques, and procedures.

Join & Write a Comment

Suggested Solutions

In a WLAN, anything you broadcast over the air can be intercepted.  By default a wireless network is wide open to all until security is configured. Even when security is configured information can still be intercepted! It is very important that you …
I have seen some questions on problems with SSH/telnet access to Cisco routers that may occur despite the fact that from a PC connected to your LAN, Internet connectivity is in place and users can access Internet sites without any issues.  There are…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

743 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now