From: Xuan.Sun@xxxxxxxxxxx
Date: Thu Aug 16 2001 - 17:45:13 GMT-3
Hi Peter
I set up a lab with the same as Fig 3-11. With both Stowe and Mammoth send
out NO-EXPORT, I get the same result in page 193. Since the community
attribute is a OPTIONAL, you need to use "send-community" to every BGP
peers, then the peer will get this attribute, no matter it is a IBGP peer
or EBGP peer.
After I add "send-community" at Sugarbush to the IBGP peer, Diamond. I can
see the NO-EXPORT attribute in Diamond.
Thank all of you to answer my question.
Regards
Peter Rybaczyk <psrsam@globalins.com>@groupstudy.com on 08/16/2001 11:43:42
AM
Please respond to Peter Rybaczyk <psrsam@globalins.com>
Sent by: nobody@groupstudy.com
To: Xuan.Sun@Seagate.com
cc: ccielab@groupstudy.com
Subject: Re: Doyle, Routing TCP/IP Vol II. PP 189: Community attribute
islost under IBGP
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 ?
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