The Local
keyword highlighted in your question means the prefix is sourced locally in that router's AS (i.e. there is no AS path).
Consider two configurations, where the routers have a BGP session with each other, and DEN-EDGE-01
is announcing 10.204.1.1/32.
Announce:10.204.1.1/32
DEN-EDGE-01----------------DEN-EDGE-02
172.16.1.203 172.16.1.204
Peering within the same ASN: Local
keyword shown
DEN-EDGE-01
in AS100 is configured to send 10.204.1.1...
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.204.1.1 mask 255.255.255.255
! Send 10.204.1.1 to DEN-EDGE-02
neighbor 172.16.2.204 remote-as 100
no auto-summary
DEN-EDGE-02
in AS100 is configured with...
router bgp 100
no synchronization
bgp log-neighbor-changes
! Just receive routes from DEN-EDGE-01
neighbor 172.16.2.203 remote-as 100
no auto-summary
!
When I receive 10.204.1.1 on DEN-EDGE-02
, there is no AS-path, only Local
DEN-EDGE-02#sh ip bgp 10.204.1.1
BGP routing table entry for 10.204.1.1/32, version 2
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Not advertised to any peer
Local <------------
172.16.2.203 from 172.16.2.203 (172.16.2.203)
Origin IGP, metric 0, localpref 100, valid, internal, best
DEN-EDGE-02#
Peering with a different ASN: AS path shown
Now we reconfigure both routers... one in AS100 and the other in AS200. DEN-EDGE-01
in AS100 is configured to send 10.204.1.1...
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.204.1.1 mask 255.255.255.255
! Send 10.204.1.1 to DEN-EDGE-02
neighbor 172.16.2.204 remote-as 200
no auto-summary
DEN-EDGE-02
in AS200 is configured with...
router bgp 200
no synchronization
bgp log-neighbor-changes
! Just receive routes from DEN-EDGE-01
neighbor 172.16.2.203 remote-as 100
no auto-summary
!
When I receive 10.204.1.1 on DEN-EDGE-02
, now we see a real AS-path, because DEN-EDGE-01
is in a different AS.
DEN-EDGE-02#sh ip bgp 10.204.1.1
BGP routing table entry for 10.204.1.1/32, version 2
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Not advertised to any peer
100 <------------
172.16.2.203 from 172.16.2.203 (172.16.2.203)
Origin IGP, metric 0, localpref 100, valid, external, best
DEN-EDGE-02#