Bgp Routing Policy - H3C S5600 Series Operation Manual

Operation Manual – Routing Protocol
H3C S5600 Series Ethernet Switches
8.0.0.0
Router A
Figure 5-9 LOCAL_PREF attribute
6) COMMUNITY
The Community attribute is used to simplify routing policy application and ease the
maintenance and management of routing policy. Community is a set of destination
addresses with the same features. It is not restricted to physical boundary and is
independent of AS. The Community attribute can be one of the following.
INTERNET. By default, the value of the COMMUNITY attributes of all routes is
INTERNET. That is, all routes belong to the Internet community by default.
Routes with this attribute can be advertised to all BGP peers.
No_EXPORT. Routes with this attribute cannot be sent to routers outside the
local AS. With the presence of the confederation, routes of this kind cannot be
advertised outside the confederation, they can only be advertised in the sub-ASs
in the confederation. (For information about confederation, refer to section
"Problems in Large-Scale BGP
No_ADVERTISE. Routes with this attribute cannot be advertised to any other
BGP peers after being received by a BGP router.
No_EXPORT_SUBCONFED. Routes with this attribute can neither be
advertised outside the local AS nor be advertised to other sub-ASs inside the
confederation after being received.

5.1.3 BGP Routing Policy

I. BGP routing policy
A BGP router filters routes in the following order.
Drops the NEXT_HOP unreachable route.
With Prefered-value specified, chooses the route with highest Prefered-value
value.
Prefers the route with highest LOCAL_PREF value.
Prefers the routes starting from the local router.
LOCAL_PREF=100
Router B
2.1.1.1
EBGP
IBGP
EBGP
AS 10
3.1.1.1
Router C
LOCAL_PREF=200
IBGP
NEXT_HOP=2.1.1.1
LOCAL_PREF=100
Router D
D=8.0.0.0
NEXT_HOP=3.1.1.1
IBGP
LOCAL_PREF=200
AS 20
Network".)
5-10
Chapter 5 BGP Configuration
5.1.4