3Com Switch 8800 Configuration Guide
Chapter 37 BGP/MPLS VPN Configuration
37-45
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Set up IBGP adjacency between PE1 and PE2 or PE1 and PE3, but not between
PE2 and PE3, that is, VPN routing information cannot be exchanged between PE2
and PE3.
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Create two VPN-instances on PE1, import VPN routes of VPN-target 100:11 and
100:12, set VPN-target for VPN routes advertised as 100:2.
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Create a VPN-instance on PE2, import VPN routes of VPN-target 100:2, set
VPN-target for VPN routes advertised as 100:11.
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Create a VPN-instance on PE3, import VPN routes of VPN-target 100:2, set
VPN-target for VPN routes advertised as 100:12.
Then PE2 and PE3 can only learn their neighbor’s routes through PE1.
Note:
In this case the configuration is focused on four points:
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Route advertisement can be controlled by VPN-target settings on different PEs.
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Routing loop is permitted only once, so that PE can receive route update messages
with AS number included from CE.
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In Hub&Spoke networking, vpn-target of VPN-instance (VPN-instance3) which is
used to release route on the PE1 cannot be the same with any vpn-target of
VPN-instance (VPN-instance2) which is used to import route on PE1.
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In Hub&Spoke networking, route-distinguisher rd2 (100:3) of VPN-instance which is
used to release route on the PE1 cannot be the same with the route-distinguisher
rd1 (100:1) or rd4 (100:4) of corresponding VPN-instances on each PE2 and PE3;
rd 1 and rd4 can be the same or not.
