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IEWB v4.1 Lab 2 – Frame-Relay Inverse Arp Troubles…

Posted by Jo on September 29, 2007

Well on Friday night the plan was to complete the 2nd half of Lab 1, but for some reason I decided to make a start on Lab 2, as I couldnt get my rack into the same state as I left it on Wednesday evening. As it is an online rack I saved all my configs offline in the hope I could restore them and pick up where I left off, but for one reason or another this didnt work out as planned. Anyway, I cracked on with Lab 2 none the less.

Bridging and Switching

This was straight forward, setting up the switches into 1 VTP domain with SW1 and the server and all the others as clients – nothing tricky here.

Setting up various EtherChannel trunks between the switches. This lab had a good mix of the different types of EtherChannels available, so was good experience to configure these. I managed all of this config without looking at the solutions guide. There was also a little bit of 802.1x which wasnt too tricky to work out. All in all I was happy with this section.

Frame Relay

This is where the fun began. Up to this point I have been OK with the Frame Relay configurations. This lab required setting up a full mesh between R1, R2, R3 and R4 but without using static layer 3 to layer 2 mappings.

For the life of me I couldnt get this to work using frame-relay inverse ARP. My understanding is that this is enabled by default, but I couldnt see any dynamic mapppings when I issued the ‘ show frame-relay map’ command, even though the DLCI’s were active when i issued the show frame pvc command. I matched my config with that in the solutions guide, but still no cigar.

In the end I decided I had no idea how to troubleshoot it, so I wiped my configs and opened up Volume I of the IEWB that has individual technology sections and mini labs. I proceeded to work through these to see if I could get a better understanding of the order of operations required to get this working correctly. Unfortunately I couldnt even get the simplest of labs working using inverse ARP, so I gave up for the night.

On top of this one of the routers in my rack was playing up (looks like it is faulty) so even if I did get it working I wouldnt have been able to complete the lab anyway.

I spoke to the support at the rack rental place, and they will be swapping out the faulty router today, so my planned session has been cancelled.


I think I have sussed out the frame-relay inverse ARP issue. It seems a reload of the router brings up the dynamic mappings when the router comes online. Does this sound right?

I now have full mesh connectivity between R1, R2, R3 and R5 after I labbed  it up. As expected there was no sign of any dynamic mappings until I reloaded all of the routers! Strange I must say.
If anyone has any way to do force this to work without a reload I would appreciate the tip, as it seems like a reload during the real lab would be a real waste of time!


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