Route Attributes
Based on route attributes, BGP routes are selected and the network administrator deploys routing
policies.
shows the main route attributes.
Table 8-2
Main route attributes
Attribute
Description
Reference Chapter
PrefVal
Huawei-specific attribute, valid
only on the device where it is
configured.
See
Preferred Values for BGP
Routes
.
Local_Pref
Determines the optimal route for
the traffic that leaves an AS.
When the device running BGP
receives multiple routes to the
same destination address but
with different next hops from
different IBGP peers, the route
with the highest Local_Pref is
selected as the optimal route.
Local_Pref Attribute for a
Device
Multi-Exit
Discriminator (MED)
Determines the optimal route for
the traffic that enters an AS. It is
similar to the metric used by an
IGP.
When the device running BGP
receives multiple routes to the
same destination address but
with different next hops from
different EBGP peers, the route
with the lowest MED is selected
as the optimal route.
See
Next_Hop
BGP discards the route with an
unreachable next hop address.
See
.
AS_Path
Records all ASs that a route
passes through from the local
end to the destination in the
distance-vector (DV) order.
AS_Path has the following
functions:
l
Prevents routing loops
among ASs.
l
Determines the selection of
the optimal route. (The BGP
route with the shortest
AS_Path is selected as the
optimal route.)
.
HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
8 BGP Configuration
Issue 02 (2014-09-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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