Thursday, 30 September 2010

MPLS Troubleshooting

I'm nearly at the end of INE's MPLS CoD, and the last few lessons are about advanced configurations for Internet Service VPNs etc. Following Keith's advice about making sure I understood the basics before continuing, I started my MPLS lab again from scratch, and came across an interesting problem..

Now, i'm assuming you know the topology for this (if not, it's over here).

I'd configured everything as per the videos, with the 192.168.3.x/32 network as loopback0 for each of the Provider devices, and MP-BGP running between the PE's to exchange VRF routing information.

I ran into a problem with VRF Cust_A, between the sites A1-Central and A2-Remote, and it was a very good test of my Troubleshooting skills...

Both PE-2 and PE-3 had learned the correct routes in their VRF routing tables, but traffic was not passing successfully;

PE-2#show ip route vrf Cust_A <- all as expected
PE-2#ping vrf Cust_A 203.1.0.1 <- timeout

PE-3 could ping the loopback0 of PE-2 (using it's own loopback0 as, but PE-2 could not ping the loopback of PE-3;

PE-2#ping 192.168.3.3 so lo 0 <- timeout
PE-3#ping 192.168.3.2 so lo 0 <- successful

PE-2 was learning the route correctly for PE-3's loopback0;

PE-2#show ip route 192.168.3.3 <- as expected, via interface to router P

The CEF table on PE-2 did not look as expected;

PE-2#show ip cef 192.168.3.3 255.255.255.255 <- not as would be expected!


I'll leave things there for now, and try and upload the screenshots..

Saturday, 25 September 2010

Cisco IOS Cookbook


I stumbled across O'Reilly's Cisco IOS Cookbook on SafariBooks the other night, and after a quick look at the preview, added it to my Bookshelf.

The book takes a particular technology of selection of technologies, and goes through each one step-by-step, in a 'Problem - You want to configure basic Frame-mode MPLS - Solution - ...' kind of way. The 'Problems' are clearly defined, and as well as giving you the complete config in one section, it then goes through each line separately. I'm looking forward to getting round to the sections on SNMP, TACACS etc, as I feel these are the technologies that suit this clear 'Problem / Solution' approach.

What i've read so far has been really good, i've downloaded the Chapters on MPLS and BGP to have on my iPad as i'm going through my INE CoD.

Speaking of which, i'm nearly at the end of the MPLS CoD now, as i'm on video 22 of 30(ish). It's still very impressive, and we're now moving onto the more exciting elements of MPLS, such as overlapping VPNs and shared services.

My plan next is to work through some scenarios, either made up by myself or from whatever resources I can find. There is an MPLS section of the INE Vol I workbook that i've got setup in Dynamips, but not had much chance to go through properly yet.

Oh, and going back to my Idea from a few weeks ago.. I've managed to get a Radius server running, so i'll try and get to that at some point in the not too distant future!

Friday, 17 September 2010

Dynamips/Dynagen and Wireshark


One of the things I've picked up from my INE MPLS CoD, is how useful Wireshark can be as a learning tool, especially when using Dynamips.

For example, it is exceptionally easy to start a capture on an interface in the middle of your topology, and see exactly what is going across the wire. This is helpful when looking at MPLS VPNs, and understanding the stacks of labels that are applied, and seeing the bottom of stack bit etc.


From your Dynagen window, the command for starting a capture is;

capture device interface filename [link-type]

'capture' starts the command

'device' is the Dynagen name of the device on which you want to run the capture, as seen from the 'list' command

'interface' is the interface on that device on which you want to run the capture

'filename' is the file where the capture will be saved (don't forget the .cap extension)

'link-type' is optional, and I've not yet played around with it myself.


To stop the capture, issue a no capture device interface command. The capture can then be opened up in Wireshark, and you can see all your networking glory ;-)


- Posted using BlogPress from my iPad



Sunday, 12 September 2010

MPLS - INE Class-on-Demand

The INE MPLS Class-on-Demand is going well. I'm about half way through now, on video 17 of 30 (but there are two 11's!).

I'm in the middle of a few lessons about how to exchange routes from the CE to the PE. The videos are broken down so there's one video per protocol- eBGP, RIP, EIGRP, and OSPF.

I would thoroughly recommend this course (and all of INE's products in general!).

I've also set my Dynamips up so that I can run through the MPLS sections of INE's R&S Vol I Workbook. It took me a while to modify their initial configs to suit my Dynamips set-up, but it's great now the initial legwork is done. At some point I'll try and work out a way of being able to switch between their initial configs easily..

- Posted using BlogPress from my iPhone

Friday, 3 September 2010

INE BGP Class-on-Demand

Checked my INE account this evening, and the recorded BGP class has now been added, yay!

I've now got to decide whether to crack on with MPLS, sit the exam sometime at the beginning of October, work through the BGP CoD before (potentially) attending a real-life course at the end of the month.

OR... take my time with the MPLS CoD, start the BGP CoD, (potentially) attend a real-life course, and then sit the Composite MPLS+BGP exam instead..

Decisions decisions...

- Posted using BlogPress from my iPhone

Thursday, 2 September 2010

MPLS - INE MPLS Class-on-Demand

As INE's MPLS CoD came out before their BGP CoD, and as i'm still supposed to be attending a real-life class on BGP, i've cracked on working through the MPLS vids.

Up to 9 of 30 now, and I really like the format. We've not actually seen how to configure anything yet, but gone through the theory of the different LIB, LFIB, and CEF tables, what the Labels consist of, how they're generated and distributed. And everything is backed up with a 'live' demo on equipment, so i've collated a short list of useful 'show' commands that i'd not used before.

show mpls ldp neighbor
show mpls ldp bindings [network]
show mpls forwarding-table [network]