From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Thu Sep 01 2005 - 20:10:24 GMT-3
Dustin,
Conditional route advertisement is on a per neighbor basis for existing
prefixes in the BGP table. IOW, the prefix already exists... the
question is should the router advertise it? Yes, if the non-exist-map
is false. No if the non-exist-map is true.
Route injection, on the other hand, allows you to ADD more specific
routes to the BGP table. It must be a more specific route though and
from a defined source.
See guidelines from before, specifically:
"The inject-map defines the prefixes that will be created and installed
into the routing table. Injected prefixes are installed in the local BGP
RIB. A valid parent route must exist; Only prefixes that are equal to or
more specific than the aggregate route (existing prefix) can be
injected."
They offer similar results, not the same. I sounds like you understand
it, because as you pointed out they are quite different.
Hence, look for wording that might lead you one way or another.
Injection example:
Rx and Ry are eBGP neighbors.
When Rx advertises prefix a.b.0.0 /16 have Ry source the more specific
route a.b.1.0 /25.
Advertise-map example:
Rx and Ry are eBGP neighbors.
Have Ry advertis prefix x.y.1.0 /24. Ensure Rx advertises z.x.2.0/16 if
x.y.1.0 /24 is no longer advertised by Ry.
HTH,
Andy
-----Original Message-----
From: dusth@comcast.net [mailto:dusth@comcast.net]
Sent: Thursday, September 01, 2005 4:00 PM
To: Edwards, Andrew M; ccielab@groupstudy.com
Subject: RE: bgp inject-map vs. neighbor advertise-map
Hi Edwards,
Yes, you are right. However, I do not know when to use b/t
<advertise-map exist-map> and the <bgp inject-map exist-map>.
These two commands offer same result besides advertise-map
populates to specific neighbor vs. bgp inject-map populate into BGP
routing table or using bgp inject-map with route-map apply to neighbor
to limit only certain segment(s) pass to the neighbor.
Any advise when to use the other other than depend on the
question in the test??
Thanks,
Dustin
-------------- Original message --------------
> Dustin,
>
> The advertise-map simply provides "tweaked logic" on
which routes to
> advertise. Such as when a non-exist-map is true, do
NOT advertise the
> exist-map. Obviously, when the non-exist-map is false,
the exist-map is
> then advertised.
>
>
> Inject-map however has a more specific function of
allowing you to
> inject "more specific" prefixes into the BGP table
with the following
> usage guidelines from CCO.
>
>
> "Inject-map
>
> Usage Guidelines
> The bgp inject-map command is used to configure
conditional route
> injection. Conditional Route Injection allows you to
originate a more
> specific prefix into a BGP routing table without a
corresponding match.
> Two route maps (exist-map and inj! ec! t-map) are
configured in global
> configuration mode and then specified with the bgp
inject-map command in
> address family or router configuration mode.
>
> The exist-map specifies the prefix that the BGP
speaker will track. This
> route map must contain a match ip address prefix-list
command statement
> to specify the aggregate prefix and a match ip
route-source prefix-list
> command statement to specify the route source.
>
> The inject-map defines the prefixes that will be
created and installed
> into the routing table. Injected prefixes are
installed in the local BGP
> RIB. A valid parent route must exist; Only prefixes
that are equal to or
> more specific than the aggregate route (existing
prefix) can be
> injected.
>
> The copy-attributes keyword is used to optionally
configure the injected
> prefix to inherit the same attributes as the aggregate
route. If th! is!
> keyword is not entered, the injected prefix will use
the default
> attributes for locally originated routes. "
>
> HTH,
>
> andy
> -----Original Message-----
> From: dusth@comcast.net [mailto:dusth@comcast.net]
> Sent: Thursday, September 01, 2005 3:06 PM
> To: ccielab@groupstudy.com
> Subject: bgp inject-map vs. neighbor advertise-map
>
>
> Hi group,
> I need some of your BGP knowledge shed me in the light
on the similarity
> and differences and when to use which option b/t these
two commands
> inject-map vs. neighbor advertise-map>.
> Besides, has extra option to advertise
> segment(s) to peer if the condition is not exist or
> exist vs. has only option to
> advertise segments(s) to peer only if the condition
exist, whatelse or
> when I! s! hould use over the other.
>
> Thanks in advance.
> Dustin
>
>
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