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IEWBv4 Lab 8 Core Tasks

Posted by Jo on October 27, 2007

This morning I made a start on the core section of Lab 8. This is classified as an 8 difficulty. The core tasks covered the usual sections. This time though it introduced MST into the mix. I have not really configured this before so got stuck in.

For the first lab in a while there were no troubleshooting tasks to start with, so no need to check through all of the initial configs. Also all of the VTP settings and VLAN’s were preconfigured on the switches, so all I needed to do was configure the trunk interfaces as detailed in the tasks. This was pretty easy going, there were the usual variations on setting these up, tasks that required minimal config to set up dynamic trunk negotiation etc etc. I am pretty good at these tasks now, and know the different combinations to get these working automatically when required.

The spanning tree section was easier than I thought. Setting up MST is as easy as setting the spanning tree mode to MST

SW1#
spanning-tree mode mst

Then assigning VLANs to these instances.

spanning-tree mst configuration
instance 1 vlan 3-7
instance 2 vlan 13-45
instance 3 vlan 52-67
instance 4 vlan 1, 1001

You can then set the root bridge per instance as follows:

spanning-tree mst 1 root primary

Once I had my trunks and MST instances configured, there was a task to ensure certain trunks were preferred within the MST instances. This was configured in the same was a PVST where the port-priority can be changed on the interfaces.

interface FastEthernet0/15
spanning-tree mst 1 port-priority 16

In this case the task asked for all traffic for VLAN’s in MST instance 1 to use the highest available trunk interface to get to the root bridge. The lowest port-priority value becomes the root port, so these can be manipulated as you want.

Once I had MST and the trunks configured I checked for Layer 2 connectivity before moving on. I had some trouble pinging between SW2 and R3. The diagram showed them on VLAN32 so I had to spend some time trouble shooting this. It turned out that as all the switches had been pre-configured in transparent mode and VLAN’s created locally, but VLAN 32 had not been created on one of the switches in the transit path. My troubleshooting method was to check all the switches and run the show spanning-tree vlan 32 command and check what ports were forwarding or blocked. When I got to SW4 there was no spanning-tree instance for this VLAN, so I had a quick check of show vlan brief and low and behold no VLAN32 in the table. Once I created this my ping sprung into action. All in all a good exercise to check basic L2 connectivity and troubleshoot any STP issues.

I got through to the BGP section, the IGP sections were fine, nothing too outrageous – just the usual authentication and route summarisation type questions. This lab needed a stub area to be created, which I got correct so nothing to worry about too much here. The redistribution task in this lab was easy also, no multiple distribution points, so no need to tag routes or anything more complex than that.

BGP was very interesting, I had recently watched the CoD on BGP so enjoyed setting up the confederations. I even got the route reflector selection correct (although it was fairly obvious). I managed to get this section working with about 10 minutes to spare before the end of my session. The BGP section had a lot of tasks in it, so I will be reviewing the ones I had to look up.

I was very pleased with my progress this morning. I got a good understanding of MST and configuring confederations, as well as some of the path selection methods within BGP.

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One Response to “IEWBv4 Lab 8 Core Tasks”

  1. […] wpman wrote an interesting post today onHere’s a quick excerptAll in all a good exercise to check basic L2 connectivity and troubleshoot any STP issues. I got through to the BGP section, the IGP sections were fine, nothing too outrageous – just the usual authentication and route summarisation type … […]

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