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Thread Index [isp-bgp] Re: Zebra as Route Reflector
On Thu, 2003-07-17 at 12:35, Adam Debus wrote:
> in theory a RR shouldn't ever see real
> traffic...just BGP exchanges, right?
>
The theory is that your RRs should be in the traffic path, although it
is possible to implement them otherwise if you are really careful and
understand what an RR does.
The issue is that an RR performs path selection according to its
perspective of the IGP distances.
So if you where to have for instance a topology such that you have
5 10 5 (igp metrics)
+------+------+------+
gw1 gw2 gw3 RR
Assuming that both gw1 & gw3 have the same external route and that all
the rest is the same, the RR will pick and reflect the path from gw3,
which is probably the wrong exit point from gw2 point of view.
Of course the example above is quite artificial, but it should
illustrate the point.
Another consideration is that when you have a network that is designed
as core/area topology, the RR is typically deployed in the area boundary
router (core attachment). One of the reasons for this is that the RR
hides paths between the two domains (core/area) and if load-balancing is
required traffic has to pass through the RR in order to be split into
multiple paths.
My advice would be to default to have the RRs in the traffic path (in
real routers), unless you really know what you are doing...
regards,
Pedro.
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