On Mon, 18 Sep 2000, Chuck Larrieu wrote:
> Having just exited a three day Global Knowledge class on BGP, let's see if
> anything sunk through this thick skull of mine. Comments in line.
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
> Peter Abraham
> Sent: Thursday, September 14, 2000 2:02 PM
> To: [EMAIL PROTECTED]
> Subject: BGP **** CCO QUESTION ** PA
>
> All these are questions that I got from the CCO BCSN tests.
>
> 1. Which command allows Router A to advertise subnet 10.1.0.0/24 in BGP?
>
> A. network 10.1.0.0
> B. network 10.1.0.0 255.255.0.0
> C. network 10.1.0.0 mask 255.255.0.0
> D. network 10.1.0.0/16
> E. network 10.1.0.0 prefix 16
>
> I have my answer as A. B,D, and E all have the wrong syntax. Is C right? I
> know that the mask length for C is 16.
I would choose C. The wording of the question is "allows Router A to
advertise". Note that none of the answers LIMIT the advertisement to
just the subnet 10.1.0.0/24. If no mask is specified, BGP assumes a
classful network. Answer A has no mask, so should properly be written
"network 10.0.0.0". C is the only properly-formatted answer which
would allow the /24 subnet. It would also allow any other subnets of
10.1.0.0/16 to be advertised, which is ok.
> CL: all are wrong with regards to producing the desired result. A) will
> place the network 10.1.0.0 into the BGP process with a mask based on the
> interface configuration. If the interface were a /8 or a /16 or a /17, the
> particular subnet would be advertised. B) syntax is wrong, as is the syntax
> of D) and E) Answer C) will place network 10.1.0.0/16 ( 255.255.0.0 0 into
> the process.
But by placing it into the process, it indeed would allow the advertising
of a more specific subnet (assuming that such subnet is learned from IGP).
The keywords are "allows to advertise".
> 2. What is the function of the BGP atomic aggregate attribute?
>
> A. To indicate that the originating router has aggregated the routes
> B. To specify the BGP router ID and AS number of the router that performed
> the route aggregation
> C. To specify the AS number of the router that performed the route
> aggregation
> D. To specify the AS number of the router that performed the route
> aggregation and the AS numbers of the non-aggregated routes
>
> Answer: A.
>
> I have searched the CISCO web site and cannot find information on BGP atomic
> aggregate attribute.
A is correct from the RFC. Note that if a BGP speaker receives a route
with the attribute set, it will pass it on with the attribute still set.
This makes C incorrect. Although the AS of the aggregator can be determined
by examining the AS path, the function is to show that the routes are
aggregated.
--
Jay Hennigan - Network Administration - [EMAIL PROTECTED]
NetLojix Communications, Inc. NASDAQ: NETX - http://www.netlojix.com/
WestNet: Connecting you to the planet. 805 884-6323
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