From: Jersey Guy (guy.jersey@gmail.com)
Date: Tue Feb 12 2008 - 16:50:03 ARST
Thanks everyone; great feedback here.........much appreciated!
Good thing is that I understood the two paragraphs this morning but was
struggling with them last night. This is good. It means that if I persevere,
I'll eventually get it. The bad part is that it is going to kill me, by the
time I DO understand everything. But hey, I made it through 200 pages of
Halabi's book AND understood *most* of it....can't be that bad....
Luan, I enjoyed your Burger King analogy. Joseph B, you're absolutely right
about walking the walk being totally different from talking the talk. I have
a good feeling that I'll get spanked real bad when I eventually get down to
configuring/making/breaking BGP on a rack.
Yeah I do have Doyle's Vol 1 & 11 but for some reason, I wanted to start
with Halabi's book. Should I worry that all my Cisco reading material is 2-3
yrs old, or will it suffice?
thanks, JG
On Feb 12, 2008 1:31 PM, Jezz Bird <jezzbird@hotmail.com> wrote:
> In a nutshell what Halabi is saying is: if you associate the MED
> attribute with an aggregated/summarised route AND supress the 'component'
> routes, the MED that you use may not necessarily the best one for ALL the
> components. The receiving AS will not know where the components are and in
> fact as he suggests they could be scattered throughout the sending AS. The
> receiving AS will not have individual MEDs for each of the components and
> this is when suboptimal routing may occur.
>
> You will need to understand this before you go to the lab but don't worry
> about it because there are bound to be some things that you just won't
> understand at first. I would suggest you have a look at Routing TCP/IP Vols
> I & II by Jeff Doyle. He explains summarisation/aggregation and BGP
> brilliantly !
>
> Regards,
>
> Jezz.
>
>
> > Date: Mon, 11 Feb 2008 21:23:55 -0500
> > From: guy.jersey@gmail.com
> > To: ccielab@groupstudy.com
> > Subject: can't understand BGP Theory
>
> >
> > From Halabi's book, Internet Routing Architectures, 2nd edition, page
> 167:
> >
> > *MEDs are somewhat handicapped by aggregation scenarios in which
> providers
> > announce a given CIDR block from multiple locations in their network and
> > suppress the smaller routes from the block. Utilizing MEDs in this
> scenario
> > could potentially result in suboptimal routing because the more-specific
> > routes of the CIDR block could be scattered throughout the AS and MEDs
> > associated with more-granular routes are no longer available.
> >
> > When using MEDs to perform what's commonly referred to as best-exit
> routing,
> > some providers leak the more-specifics of their CIDR blocks to select
> peers
> > to remove the offshoots introduced by aggregation. The problem with this
> is
> > that controlling the more-specific announcements is sometimes complex,
> and
> > failure to do so can result in some very suboptimal routing situations.
> > *
> > I read the above two paragraphs five times but didn't understand it.
> Which
> > of the following is true:
> >
> > a) I have no choice but to understand this stuff, to pass the lab. I
> need to
> > understand *everything* in Halabi's book, period.
> > b) The lab is tough but not THAT tough. I can skip certain convoluted
> > sections of every topic and still manage to get by.
> > c) Forget it. I am not going to make it. MED is a piece of cake; what's
> so
> > hard to understand??
> > d) I need to read "How to grow gray matter and raise IQ" book before
> > Halabi's.
> >
> > Thing is....how thoroughly do I need to pound away at theory/reading
> before
> > hitting the equipment, lab scenarios and excercises?
> >
> >
> > thanks, JG
> >
> > _______________________________________________________________________
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>
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