Huawei Quidway NetEngine80E Configuration Manual page 932

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
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*>
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The preceding command output shows that Router A selects the route 10.11.0.0/16 learned from
ISP1 and the route 10.22.0.0/16 learned from ISP2.
# Display detailed information about the route 10.22.0.0/16 on Router A.
[RouterA] display bgp routing-table 10.22.0.0
BGP local router ID : 10.1.2.1
Local AS number : 65001
Paths:
BGP routing table entry information of 10.22.0.0/16:
From: 10.1.3.2 (10.1.3.2)
Route Duration: 00h14m14s
Direct Out-interface: GigabitEthernet0/0/1
Original nexthop: 10.1.3.2
Qos information : 0x0
AS-path 200, origin incomplete, pref-val 120, valid, external, best, select,
active, pre 255
Advertised to such 2 peers:
BGP routing table entry information of 10.22.0.0/16:
From: 10.1.2.2 (10.1.2.2)
Route Duration: 00h07m54s
Direct Out-interface: GigabitEthernet0/0/0
Original nexthop: 10.1.2.2
Qos information : 0x0
AS-path 300 100, origin incomplete, pref-val 0, valid, external, pre 255, not
preferred for PreVal
Not advertised to any peer yet
The preceding command output shows that two routes 10.22.0.0/16 are available in the BGP
routing table of Router A and that the route with the next hop address 10.1.3.2 is selected because
its PrefVal (120) is greater than the PrefVal (0) of the route with next hop address 10.1.2.2. The
PrefVal value is sufficient enough to determine the optimal route, and therefore, Router A does
not compare other route attributes.
The preceding examples show that PrefVal values can be configured as required to control the
traffic forwarding path.
Local_Pref
BGP prefers the route with the highest Local_Pref during BGP route selection.
The Local_Pref attribute is used to determine the optimal route when traffic leaves an AS. The
Local_Pref attribute is available only to IBGP peers and is not advertised to other ASs.
Table 8-18
Table 8-18 Methods to modify the Local_Pref value
Method
Run the default local-preference command. This method sets a default Local_Pref for the
Issue 02 (2014-09-30)
10.22.0.0/16
2 available, 1 best, 1 select
10.1.3.2
10.1.2.2
lists two methods to modify the Local_Pref value.
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10.1.3.2
10.1.3.2
10.1.2.2
Usage Scenario
routes that the local device advertises to IBGP
peers.
8 BGP Configuration
0 200?
120 200?
0 300 100?
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