From: Peter Rybaczyk (psrsam@xxxxxxxxxxxxx)
Date: Thu Aug 16 2001 - 15:43:42 GMT-3
Xuan,
I believe I see your point here as I've struggled with this example as well. It
looks to me like the example 3-55 on p.193 (you mean 193 instead of 293 right?)
is given out of sequence with the explanation. The NO-EXPORT community is
propagated to IBGP peers but not to EBGP peers so that attribute does not get
lost when a route containing it is advertised to an IBGP peer. It's the
NO-ADVERTISE community attribute that's not passed on to either IBGP or EBGP
peers. So if the example 3-55 reflected the configuration that's shown for
Stowe and Mammoth both routes for 192.168.199.0 should have the community
attribute set to NO-EXPORT. It looks to me like the display was done after
Mammoth was configured but before Stowe. There is the other possibility that
part of the display (Example 3-55) that would show the community attribute for
the route from Sagebrush got cut off, which can happen during book
editing/production process.
I find Doyle's books to be head and shoulders above some of the other CCIE prep
publications, but I am not kidding myself about them being perfect. There are a
couple other inconsistencies in Volume II, although I think that over all the
BGP section is superb.
HTH,
Peter
Xuan.Sun@Seagate.com wrote:
> I have set up the network based on Fig 3-11. Please refer to the Routing
> TCP/IP Volume II, Page 189. I can not draw it here.
>
> The idea is to use NO-EXPORT to control the internal network address to
> leak to AS 300. So the router under AS 300 only see the aggregate address,
> not the specific-route. But this solution is not worked in one condition.
>
> If the link between Diamond and Burke broken and the link between Stowe and
> Sugarbush broken, you will see all the specific routes in Burke router. The
> reason is the community attribute of NO-EXPORT is lost when it distributes
> in the IBGP peer. Under Example 3-55 in Page. 293, it has showed two BGP
> entries for 192.168.199.0. One is from EBGP peer, obviously has NO-EXPORT
> attribute. One is from IBGP peer, no NO-EXPORT.
>
> Am I rigtht ?
> **Please read:http://www.groupstudy.com/list/posting.html
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