Posted by: Richard @ Configureterminal.com | February 18, 2008

Week 6 summary

I completed week 6 of my studies last night and reached a landmark; I have now finished looking at all of the CCIE IGP’s and I am now ready to move into the ‘unknown’.… Many of the technologies I will be covering from now on are technologies that I have studied in the past or deployed at a basic level on a production network but they have never really caused me to experience ‘decompression sickness’– as we should all know it’s one thing learning the theory and another thing doing it in real life, and that’s what the CCIE qualification tries to distinguish between!  BGP is certainly one of the areas that I have little ‘real-life’ exposure to and will be the focus of my studies for the next two weeks.  I will then take a week to step back and review everything I have covered up-to that point.

My notes are almost ready to be published as Ebooks on the Lake Tawakoni social web that is the ‘tinternet’.  The documents should hopefully be ready over the course of the next few days.

I noticed that I hadn’t made any notes about summarisation last week and so I had to squeeze in a small amount of time to take a look at it, here are some of my notes:

  • RIP version 2 and EIGRP à manual route summarization is configured on the interface that will be advertising the summary
    • RIP Configuration
      • ip summary-address rip ‘ip-address’ ‘mask’
        • A route to Null0 is automatically added
        • You can’t create a ‘supernet’ with RIP summarization
          • e.g. 172.16.0.0 255.254.0.0 won’t work
        • You can only use one summarization statement per classful network
        • Last child route lost/removed à summary address removed from RIP database
        • RIPv2 uses lowest metric of all current child routes
        • Metric is calculated at route initialization or when there are metric modifications of specific routes at advertisement time, and not at the time the aggregated routes are advertised
    • EIGRP Configuration
      • ip summary-address eigrp ‘as no.’ ‘ip-address’ ‘mask’ [‘ad’]
        • A route to Null0 is automatically added
          • Default AD is 5 and is only used locally (not advertised)
            • Neighbours use AD 90
          • If using to inject default route remember the AD 5 might override a learned default route (set the AD higher) à called a ‘floating summary route’
  • RIP version 2 and EIGRP also both perform autosummarization on routes that are advertised across classful network boundaries
    • To disable
      • no auto-summary
        • Under the routing process

  • OSPF offers two different route summarization commands à
    • To summarize routes from one OSPF area to another
      • area ‘no.’ range ‘ip-address’ ‘mask’ [advertise | not-advertise] [cost ‘cost’]
        • A route to Null0 is NOT automatically added
          • Remember to add it
        • advertise = Type 3 LSA generated
        • not-advertise = ‘DoNotAdvertise’ – Type 3 LSA suppressed à networks hidden from others
    • To summarize routes learned via redistribution
      • summary-address ‘ip-address’ ‘mask’ [not-advertise] [tag ‘tag’]
        • On the ASBR
        • A route to Null0 is NOT automatically added

 

  • Benefits:
    • Bandwidth is saved on links
    • Summarising router maintains only one route and therefore saves memory
    • Summarising router + neighbours save CPU resources, because packets are evaluated against less entries in its routing table

You can isolate topology changes from other routers (e.g. flapping)


I am still working on the ‘studied so far’ lab, I am planning to squeeze it in outside of my daily 2 hours of studying which will also keep things fresh in my mind whilst moving on through the rest of the CCIE learning track.

I was introduced to a marvelous product this week that I have been planning to find for some time but had been content using Wintabber, the product is:

Putty Connection Manager

It takes the putty client into the same realms as SecureCRT with its tabbed sessions and saved sessions (existing and/or new database) and allows me to carry on using my favourite telnet/SSH client J  And, the best thing about it is that it’s free!

Here is the breakdown of my sixth week of studying:

Study time:
Study Hours = 15  inc.
Lab Hours = 0.5

Total study time so far:
Total Study Hours = 82  inc.
Total Lab Hours = 10

What I have studied this week:
OSPF
Route
summarisation

Recent test scores:
OSPF = 11/12

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