Redistribution Of Igps To Bgp - Cisco ASR 9000 Series Routing Configuration Manual

Configuring a VPN Routing and Forwarding Instance in BGP
Command or Action
Step 16
as-override
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#
as-override
Step 17 allowas-in [ as-occurrence-number ]
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#
allowas-in 5
Step 18 route-policy route-policy-name in
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#
route-policy pe_ce_in_policy in
Step 19 route-policy route-policy-name out
Example:
RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#
route-policy pe_ce_out_policy out
Step 20
commit

Redistribution of IGPs to BGP

Perform this task to configure redistribution of a protocol into the VRF address family.
Even if Interior Gateway Protocols (IGPs) are used as the PE-CE protocol, the import logic happens through
BGP. Therefore, all IGP routes have to be imported into the BGP VRF table.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Purpose
Configures AS override on the PE router. This causes the PE
router to replace the CE's ASN with its own (PE) ASN.
This loss of information could lead to routing loops; to
Note
avoid loops caused by as-override, use it in conjunction
with site-of-origin.
Allows an AS path with the PE autonomous system number (ASN)
a specified number of times.
Hub and spoke VPN networks need the looping back of routing
information to the HUB PE through the HUB CE. When this
happens, due to the presence of the PE ASN, the looped-back
information is dropped by the HUB PE. To avoid this, use the
allowas-in command to allow prefixes even if they have the PEs
ASN up to the specified number of times.
Specifies a routing policy for an inbound route. The policy can
be used to filter routes or modify route attributes.
Specifies a routing policy for an outbound route. The policy can
be used to filter routes or modify route attributes.
Implementing BGP