05_07_配置BGP作为PE和CE路由器之间的路由协议

2019年7月27日 07:12 作者：金淼淋分类：MPLS  585

MPLS VPN Implementation
YES LAB
Configuring BGP as the Routing
Protocol Between PE and CE Routers
YES LAB
wwwveslab net Outline
YES LAB
— Overview
— Configuring a per-VRF BGP Routing Context.fidH4$+VRF
What Are the Reasons for Limiting the Number of Routes in a VRF?
— Limiting the Number of Prefixes Received from
a BGP
— Limiting the Total Number of VRF Routes.
— Identifying AS-Override Issues.
— Identifying Allowas-in Issues.
— Implementing SOO for Loop
— Summary
wwwveslab net AS-Override:
Implementation
YES LAB
— New AS path update procedures have been implemented
to reuse the same AS number on all VPN sites.
— The procedures allow the use of private and public AS
numbers.
— The same AS number may be used for all sites.
wwwveslab net AS-Override:
Command
Router f) #
neighbor ip—address as—override
• This command configures the AS-override AS path update
procedure for the specified neigh bor.
override
AS-override is configured for CE EBGP neighbors in the VRF
address family of the BGP
EBGPå5ßfidHAS-overrideo
wwwveslab net
YES LAB Allowas-in:
The Issue
YES LAB
VPN-B
VPN-A
CE
— Customer site links two VPNs.$h-lidikfifiZi#j+vpN
— Not a usual setup (traffic between VPNs should not flow over
the customer site).
— Sometimes used for enhanced security. Allowas-in:
Implementation
YES LAB
•The allowas-in BGP option disables the AS
path check on the PE router:
allowas-in
— The number of occurrences of the PE router AS
number is limited to suppress real routing loops.
— The limit has to be configured.
— The PE router will reject the update only if its AS
number appears in the AS path more often than
the configured limit.
wwwveslab net Allowas-in:
Command
Router (config—router) #
neighbor allowas—in number
This command disables the traditional BGP AS
path check.
YES LAB
An incoming update is rejected only if the AS number of the
PE router appears in the AS path more often than the
configured
wwwveslab net Implementing SOO for Loop
Prevention
YES LAB
Site B
65213
Site A
AS 65213
CE-BGP-AI
10.1.0.0/16 65213
P-Network
AS 65115
10.1.0.0/16 65115 65115
CE-BGP-R
PE-Site-X
ilo.1.o.0/16
PE-Site-y
CE-BGP-A'L
10.1.0.0/16 65115 65115
•AS path-based BGP loop prevention is bypassed with the AS-override and
MJBGPE$
allowas-in features.
wwwveslab net Implementing SOO for Loop Prevention
(Cont.)
Inbound EBGP Update
Router (config) #
te—map name permit seq
ma t ch condi t ions
set extcommunity soo extended—communi ty—val ue
Creates a route map that sets the SOO attribute
map, TS00JÆt'±
Router f) #
neighbor ip—address route—map name in
• Applies an inbound route map to the CE EBGP neighbor
EBGPQ[IE
wwwveslab net
YES LAB Implementing SOO for Loop
Prevention (Cont. )
Other Inbound Routing Updates
Router (config—if) #
ip vrf sitemap route—map—name
YES LAB
Applies a route map that sets the SOO extended community
attribute to inbound routing updates received from this
interface.
wwwveslab net