Passed MPLS and BGP

I passed the MPLS and BGP exam on Thursday. This time around the questions seemed harder, but with the extra couple of weeks of study I passed fairly easily. Looking back on it I should have done the separate exams. The MPLS Fundamentals book is good, but not enough for the exam. There were a few things I had to rely on the "MPLS and VPN Architectures CCIP Edition" book for. I had underestimated the BGP section. While I have worked for an ISP before I didn't really understand some of what was happening under the covers (even though I new enough to make BGP do what I wanted). The "Internet Routing Architectures" book is still one of the better books for this exam, but it is not enough. I would say you need to do a little general design research as well.

On to BSCI. I am not really in a hurry to do the exam - I am planning on doing enough routing, IPv6 and Multicast study for the BSCI so that I am at CCIE written level. Once I have done that I'll do the exam then move on to studying the rest of the CCIE written.

Post exam

I missed out on passing. I was close - but no cigar. I would say the exam tested my BGP more than I expected. The MPLS portion focussed on a couple of areas I did not expect. There was a reasonable amount on the ATM side of things which was a surprise to me. I am not sure if Cisco uses "adaptive" exam technology, but it sure feels like it (I am sure I stuffed up an early question and then got hammered on that technology).

The scores at the end of the exam were really useless as far as re-focussing my study. The sections on it were:

• Technology
• Basic Implementation and Configuration
• Advanced configuration

It might as well have said theory, easy questions and hard questions.

Would have been nice if they split it up into maybe a few of the MPLS technologies, a few of the BGP topology types and then a catch all for the rest of BGP and MPLS.

BGP and MPLS exam

I've bitten the bullet and scheduled the MPLS and BGP exam for tomorrow. I've really spent way more time tinkering with BGP in the last week than I have with MPLS. That's probably more of a reflection of where my current interest is than what I need to know for the exam. I am happy with what I know about BGP now (I'd call it almost CCIE level knowledge). The MPLS study that I have done over the last week has been mainly focussed on the MPLS VPN and basic MPLS subjects. I did a final read through of the ATM subjects in the Fundamentals book earlier in the week (I know that is a bit of a weak spot in my knowledge). I haven't really studied AToM and VPLS that much in the last week, I don't really know them in depth but I am happy that it will be enough for the exam.

The things I KNOW I need to remember for the exam are:

• You need to be able to route to the IP address used for the router-id by LDP in order for an LDP session to establish (I keep reminding myself and forgetting when I lab something up)
• The different VPN types and overlay, peer-to-peer, extranet etc.
• BGP route selection process (really happy I know my stuff for this)
• Configuring VRFs and using multiple route-targets to allow overlapping and other types of VPNs.
• Using OSPF between the CE and PE routers (sham links are something I spent a while playing with on dynamips)
• Confederations, Route reflectors and how they impact BGP advertisements.
• BGP attributes and how to change them and what they REALLY do
• Multi-protocol BGP - address-family vpnv4 and address-family ipv4 vrf and what to put under each

I am sure there will be some general MPLS and LDP type questions (ie what tag would router x use to forward a packet, how does the icmp packet too big get delivered, how does LDP find neighbors etc). I am pretty happy I have that sorted.

I'd have to say once I had done an initial read of a few books I got the biggest value from using dynagen / GNS3 labbing things up and using wireshark to look at packets. I really understood HOW LDP worked once I saw the packets. The book didn't really say why LDP used a UDP stream and a TCP stream. After seeing it the UDP stream is just for hello packets and finding a neighbor via multicast. The TCP stream is for advertising labels (using the LDP router-ids for the source and destination). Why couldn't the Fundamentals book just say that?

The other thing I am always slipping up on is BGP neighbor establishment. I have a habit of mistyping IP addresses, mistyping AS numbers or forgetting eBGP multihop. I tend to struggle for a while and turn on debug ip bgp and then just recheck my configurations. I keep forgetting how powerful the show ip bgp neighbors command is.

Visio Icons

I'm sick of trying to find the Cisco Visio icons. The generic ones are at:
http://www.cisco.com/web/about/ac50/ac47/2.html

Re-focussing study

I was recently made redundant (very unexpected given that I only started the job 6 weeks ago), so I've spent a little time contemplating study and work. I've decided the current choices focus more on IP routing and switching rather than MPLS. So I'm refocussing on my CCIE written. Even though it is not a stand alone certification it does show you are serious.

So it's back to the books looking at snippets of information like - unicast flooding being caused by asymmetric routing or flapping links and STP TCNs.

Baby Giants and Jumbo Frames

Someone asked me about Jumbo frames so I thought I would take a bit of a look (partly because I have to look at Baby Giants anyway). Here is what I have found so far:

• Baby Giants have an MTU of up to 1600 bytes. Jumbo frames can be over 9000 bytes (the exact size depends on the switch platform and possibly IOS).
• Some Cisco switches and routers don't support baby giants or jumbo frames, usually because of ASIC limitations.
• If you just want baby giants so that you can put a single MPLS tag on a frame you can try changing the interface to use 802.1q trunking and then place your MPLS traffic in the native VLAN. This changes the MTU to 1504 (so it fits one tag) and is supported on most switches.
• The interface counters will count the baby giant or jumbo frame as being over-sized even if the interface can support it - this is cosmetic.
• Some devices allow you to set a separate MTU for 10/100 and Gigabit interfaces. One of these is the 3750. For the 10/100 interfaces you use the system mtu number command. For the Gig interfaces you use the system mtu jumbo number command. If you set the system mtu but not the system mtu jumbo then the Gig interfaces use the system mtu. The reason for the two commands is that the 10/100 interfaces only support a lower MTU than the Gig interfaces. Other than trying the commands or looking up on the Web there does not seem to be a way to find out what the maximum acceptable sizes are.

CCIP MPLS and BGP combo exam

I've decided I am going to do the CCIP combo MPLS and BGP exam. There are a couple of reasons - the biggest one is time. I really want to get the CCIP out of the way before the end of September and the CCIE written done by the end of October. Realistically the CCIE written exam will probably take more than a month to study for (even though September will be routing month). Even though I am going to do the BSCI in September (my BSCI exam expired about two or three years back) I still think I'll need a good four weeks for the CCIE written - between switching, multicast, frame-realy and QoS. It should all just be revision as I did the written a few years back and have done some hard core study for it a few months back.

I'm half thinking i should book the combo exam for two weeks time to put a little pressure on myself (I'm easily distracted at the moment). Looking at the BGP exam outline I keep thinking how hard could it really be... and then I remember how hard it really can be.

Back to the books.