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AS_PATH rules for BGP/MP-BGP

jwstric22
Level 1
Level 1

See attached Physical TOPO.

CE(s) AS is 65100

PE(s) AS is 65501

CE1 vrf 100 (vrf lite) peered to PE1 vrf 100

CE2 vrf 100 (vrf lite) peeredto PE2 vrf 10.

CE1 is advertising 11.100.0.0/24

1.  At PE1; we see the route.  Since CE1 originated the route; its AS_PATH is set to CE1 AS.

RP/0/RSP1/CPU0:PE1-ASR9K-AG04-1#show bgp vrf 100 ipv4 unicast

BGP VRF 100, state: Active

BGP Route Distinguisher: 1:100

VRF ID: 0x60000001

BGP router identifier 21.1.101.1, local AS number 65501

BGP table state: Active

Table ID: 0xe0000010   RD version: 93478

BGP main routing table version 93478

Status codes: s suppressed, d damped, h history, * valid, > best

              i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network            Next Hop            Metric LocPrf Weight Path

Route Distinguisher: 1:100 (default for vrf 100)

*> 11.100.0.0/24      121.1.201.1              0             0 65100 ?

*>i12.100.0.0/24      21.6.101.1               0    100      0 ?

*> 21.1.201.1/32      0.0.0.0                  0         32768 ?

2.  At PE2; we see the route.  Sent to PE2 (via a route reflector not shown). 

RP/0/RSP1/CPU0:PE2-ASR9K-AG04-2#show bgp vrf 100 ipv4 unicast

BGP VRF 100, state: Active

BGP Route Distinguisher: 1:100

VRF ID: 0x60000002

BGP router identifier 21.2.101.1, local AS number 65501

Non-stop routing is enabled

BGP table state: Active

Table ID: 0xe0000011   RD version: 91134

BGP main routing table version 91134

BGP NSR Initial initsync version 4294967295 (Not Reached)

Status codes: s suppressed, d damped, h history, * valid, > best

              i - internal, r RIB-failure, S stale, N Nexthop-discard

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network            Next Hop            Metric LocPrf Weight Path

Route Distinguisher: 1:100 (default for vrf 100)

*>i11.100.0.0/24      21.1.101.1               0    100      0 65100 ?

Here is where it gets sticky, and I believe I'm missing some rule set of MP-BGP.  Unless we set as-override at PE2, PE2 will never send an update to CE2.  My belief in the scenerio was that PE2 would sent the advertisement but CE2 should dampen it unless it unless we set it to allow our own AS in , allow-as in.

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