Huawei Quidway NetEngine80E Configuration Manual page 979

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
Route Attribute
AS_Path
Origin
MED
Peer type
IGP cost
Cluster_List
In most cases, BGP does not advertise the routes learned from an AS to the AS again. When
RRs are deployed, such routes may be advertised to the AS again although routing loops may
occur. Using the Cluster_List attribute can prevent such routing loops.
Originator_ID
If routes carry the Originator_ID, the originator ID is substituted for the router ID during route
selection. The route with the smallest Originator_ID is preferred.
The Originator_ID attribute is four bytes long and is generated by an RR. It carries the router
ID of the route originator in the local AS.
l
l
The following example shows how Originator_ID is used during BGP route selection. In
8-27, an IBGP peer relationship is established between each two neighboring devices in AS
65001. The router IDs of Router B and Router C are 2.2.2.9 and 3.3.3.9, respectively, and they
function as RRs. Router D is a client of Router B, and Router E is a client of Router C. Router
D and Router E are configured to import the route 10.1.4.0/30 to BGP.
Issue 02 (2014-09-30)
Route Learned
from Router B
-
IGP
0
IBGP
3
0.0.0.2, 0.0.0.1
When a route is reflected by an RR for the first time, the RR adds the Originator_ID to this
route. If a route already carries the Originator_ID attribute, the RR does not create a new
one.
After receiving the route, a BGP speaker checks whether the Originator_ID is the same as
its router ID. If Originator_ID is the same as its router ID, the BGP speaker discards this
route.
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
Route Learned
from Router C
-
IGP
0
IBGP
3
0.0.0.3
8 BGP Configuration
Comparison
The same length.
The same.
The same.
The same.
The same.
The route learned
from Router C is
optimal.
Figure
954