Route Attributes - Huawei Quidway NetEngine80E Configuration Manual

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing

Route Attributes

Based on route attributes, BGP routes are selected and the network administrator deploys routing
policies.
Table 8-2 Main route attributes
Attribute
PrefVal
Local_Pref
Multi-Exit
Discriminator (MED)
Next_Hop
AS_Path
Issue 02 (2014-09-30)
Table 8-2 shows the main route attributes.
Description
Huawei-specific attribute, valid
only on the device where it is
configured.
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.
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.
BGP discards the route with an
unreachable next hop address.
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.)
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8 BGP Configuration
Reference Chapter
See 8.4.3 Configuring
Preferred Values for BGP
Routes.
See 8.4.4 Configuring a Default
Local_Pref Attribute for a
Device.
See 8.4.5 Configuring MED
Attributes for BGP Routes.
See 8.4.6 Configuring
Next_Hop Attributes for
Routes.
See 8.4.7 Configuring AS_Path
Attributes for Routes.
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