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Home > Archive > alt.certification.cisco > November 2002 > BGP question -- CCNP BSCN
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BGP question -- CCNP BSCN
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| zsquad 2002-11-29, 12:24 am |
| All,
I'm going thru the BSCN book (by ciscopress). Regarding BGP
Synchronization, on page 333 with the diagram of 6 routers and a
scenario with and w/o synchronization, I find the setup conflicting.
In the scenario where synchronization is used, they state that there
is no IGP running and that the router A would never advertise out the
172.16.0.0 network. My contention is that if there is no IGP running
in this network setup how would the A, C, D and B routers ever
establish IBGP connections. After all it is not a 'physical' full
mesh with each other. Some kind of IGP should be running to allow for
IBGP establishment. Unless it is implicitly using static routes (only
the statics to facilitate router to router reachability) and nothing
more. If that is the case, then it is not clearly stated. It merely
states that there is no IGP running in the AS 65500.
Well, just a stickler that I've been puzzling over. I may have missed
a point, but if someone who has gone thru this exercise/book, please
advise.
PS. Correct me if i'm wrong, but should an IGP/STATIC be running in
an AS regardless if the BGP routers in a given AS are physically
full-meshed. This way, IGBP can be established if it is physically
multiple hops away? Or is it that you do not need and IGP in an AS if
all routers are IGBP peered?
Thanks.
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| Hansang Bae 2002-11-29, 11:24 am |
| In article <e53cc1f8.0211282140.24739f32@posting.google.com>,
zsquad@onebox.com says...
> I'm going thru the BSCN book (by ciscopress). Regarding BGP
> Synchronization, on page 333 with the diagram of 6 routers and a
> scenario with and w/o synchronization, I find the setup conflicting.
> In the scenario where synchronization is used, they state that there
> is no IGP running and that the router A would never advertise out the
> 172.16.0.0 network. My contention is that if there is no IGP running
> in this network setup how would the A, C, D and B routers ever
> establish IBGP connections. After all it is not a 'physical' full
> mesh with each other. Some kind of IGP should be running to allow for
> IBGP establishment.
> Unless it is implicitly using static routes (only
> the statics to facilitate router to router reachability) and nothing
> more. If that is the case, then it is not clearly stated. It merely
> states that there is no IGP running in the AS 65500.
[snip]
You're correct. What they probably meant to say was "that bgp is not
redistributed into IGP" Without an IGP or static routes of some sort, the
routers would never be able to reach one another.
--
hsb
"Somehow I imagined this experience would be more rewarding" Calvin
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