Run the display ip routing-table vpn-instance command on PEs, and you can see the routes
to the VPNs of the peer CEs.
Take PE2 for example.
[PE2] display ip routing-table vpn-instance vpn1
Route Flags: R - relied, D - download to fib
------------------------------------------------------------------------------
Routing Tables: vpn1
Destinations : 7 Routes : 7
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.1.1.0/24 BGP 255 0 RD 1.1.1.9 Vlanif30
10.2.1.0/24 Direct 0 0 D 10.2.1.2 Vlanif40
10.2.1.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.2.1.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
100.1.1.0/24 BGP 255 0 RD 1.1.1.9 Vlanif30
200.1.1.0/24 BGP 255 0 D 10.2.1.1 Vlanif40
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
Enable debugging of the BGP Update packets on PE2. The debugging information shows that
PE2 advertises the route to 100.1.1.0/24 and the AS path information is "100 600".
<PE2> terminal monitor
<PE2> terminal debugging
<PE2> debugging bgp update vpn-instance vpn1 peer 10.2.1.1 verbose
<PE2> refresh bgp vpn-instance vpn1 all export
*0.4402392 PE2 RM/7/RMDEBUG:
BGP.vpn1: Send UPDATE to 10.2.1.1 for following destinations :
Origin : Incomplete
AS Path : 100 600
Next Hop : 10.2.1.2
100.1.1.0/24,
Run the display bgp routing-table peer received-routes command on CE2, and you can see
that CE2 does not accept the route to 100.1.1.0/24.
[CE2] display bgp routing-table peer 10.2.1.2 received-routes
Total Number of Routes: 3
BGP Local router ID is 10.2.1.1
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 10.1.1.0/24 10.2.1.2 0 100?
* 10.2.1.0/24 10.2.1.2 0 0 100?
* 10.2.1.1/32 10.2.1.2 0 0 100?
Step 2 Configure BGP ASN substitution.
Configure BGP ASN substitution on PEs.
# Take PE2 for example.
[PE2] bgp 100
[PE2-bgp] ipv4-family vpn-instance vpn1
[PE2-bgp-vpn1] peer 10.2.1.1 substitute-as
In the route advertised to CE2 by PE2, you can see that the AS path information of 100.1.1.0/24
changes from "100 600" to "100 100".
*0.13498737 PE2 RM/7/RMDEBUG:
BGP.vpn1: Send UPDATE to 10.2.1.1 for following destinations :
Origin : Incomplete
AS Path : 100 100
Next Hop : 10.2.1.2
100.1.1.0/24
Display the routing information and routing table received by CE2.
Quidway S7700 Smart Routing Switch
Configuration Guide - VPN 3 BGP MPLS IP VPN Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
206
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