Huawei Quidway S5600 Series Operation Manual page 355

Operation Manual – Routing Protocol
Quidway S5600 Series Ethernet Switches-Release 1510
Chooses routes in the order of the route Origin type, that is, the order of IGP, EGP,
and Incomplete.
Prefers the route with the lowest MED value.
Chooses the route learnt from RBGP, the route learnt from confederation and the
route learnt from the IBGP in turn.
Prefers the route with the smallest originator ID.
Prefers the route with the smallest router ID>
II. Assigning description information for a peer or peer group
You can assign descriptive information for a BGP peer or peer group for ease of
network maintenance.
Description information assigned for BGP peer and description information for peer
group are independent of each other.
III. BGP route advertising policy
In VRP implementations, a BGP router adopts the following policies to advertise routes.
Sends the optimal route to its peers when multiple valid routes exist.
Sends only the routes used by itself to its peers.
Sends all the EBGP routes to all its BGP peers, including the EBGP peers and
IBGP peers.
Does not send IBGP routes to its IBGP peers.
Sends IBGP routes to its EBGP peers.
Sends all its BGP routes to the new peer once a new BGP connection is
established.
5.1.4 Problems in Large-Scale BGP Networks
I. Route aggregation
BGP routing tables in a large-scale network may be huge in size. Route aggregation
can largely diminish the size of a routing table.
Route aggregation aggregates multiple routes to one route. It enables a BGP router to
replace multiple specific routes with one equivalent aggregated route.
VRP supports automatic route aggregation and manual route aggregation. In the
manual route aggregation mode, you can control the attribute of the aggregated routes
and determine whether to send the specific routes or not.
II. BGP route dampening
BGP route dampening is used to solve the problem of route instability. Route instability
mainly takes the form of route flaps, that is, a route appears and disappears repeatedly
in the routing table.
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Chapter 5 BGP Configuration