Modify BGP routing using BGP origin-code attribute
Experimental topology
Basic configuration:
R1
L0:1.1.1.1/32
L1:11.1.1.1/32
E1/0:10.1.12.1/24
E1/1:10.1.14.1/24
R2
L0:2.2.2.2/32
L1:22.2.2.2/32
E1/0:10.1.12.2/24
E1/1:10.1.24.2/24
R4
L0:4.4.4.4/32
L1:44.4.4.4/32
E1/0:10.1.24.4/24
E1/1:10.1.14.4/24
Configure IGP (RIP):
R1
Router rip
Version 2
Network 1.0.0.0
Network 10.0.0.0
No auto-summary
R2
Router rip
Version 2
Network 2.0.0.0
Network 10.0.0.0
No auto-summary
R4
Router rip
Version 2
Network 4.0.0.0
Network 10.0.0.0
No auto-summary
Configure BGP:
Router bgp 1
Bgp router-id 1.1.1.1
Bgp log-neighbor-changes
Network 1.1.1.1 mask 255.255.255.255
Network 2.2.2.2 mask 255.255.255.255 backdoor
Network 4.4.4.4 mask 255.255.255.255 backdoor
Network 11.1.1.1 mask 255.255.255.255
Neighbor 2.2.2.2 remote-as 23
Neighbor 2.2.2.2 ebgp-multihop 2
Neighbor 2.2.2.2 update-source Loopback0
Neighbor 4.4.4.4 remote-as 23
Neighbor 4.4.4.4 ebgp-multihop 2
Neighbor 4.4.4.4 update-source Loopback0
R2
Router bgp 23
Bgp router-id 2.2.2.2
Bgp log-neighbor-changes
Network 1.1.1.1 mask 255.255.255.255 backdoor
Network 2.2.2.2 mask 255.255.255.255
Network 22.2.2.2 mask 255.255.255.255
Neighbor 1.1.1.1 remote-as 1
Neighbor 1.1.1.1 ebgp-multihop 2
Neighbor 1.1.1.1 update-source Loopback0
Neighbor 4.4.4.4 remote-as 23
Neighbor 4.4.4.4 update-source Loopback0
R4
Router bgp 23
Bgp router-id 4.4.4.4
Bgp log-neighbor-changes
Network 1.1.1.1 mask 255.255.255.255 backdoor
Network 4.4.4.4 mask 255.255.255.255
Network 44.4.4.4 mask 255.255.255.255
Neighbor 1.1.1.1 remote-as 1
Neighbor 1.1.1.1 ebgp-multihop 2
Neighbor 1.1.1.1 update-source Loopback0
Neighbor 2.2.2.2 remote-as 23
Neighbor 2.2.2.2 update-source Loopback0
View the routing table of R1: origin is I, which indicates the route learned from IGP.
R1#sh ip bgp
BGP table version is 5, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, I-internal
R RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter
X best-external, an additional-path, c RIB-compressed
Origin codes: I-IGP, e-EGP,?-incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
R 2.2.2.2/32 4.4.4.4 0 23 i
R > 2.2.2.2 0 023 I
R 4.4.4.4/32 4.4.4.4 0 0 23 i
R > 2.2.2.2 0 23 I
* 22.2.2.2 Universe 32 4.4.4.4 0 23 I
* > 2.2.2.2 00 23 I
* 44.4.4.4Compact 32 4.4.4.4 0 0 23 I
* > 2.2.2.2 0 23 I
View the routing table of 22.2.2.2 44.4.4.4:
R1#sh ip bgp 22.2.2.2
BGP routing table entry for 22.2.2.2/32, version 4
Paths: (2 available, best # 2, table default)
Advertised to update-groups:
eighteen
Refresh Epoch 1
twenty-three
4.4.4.4 (metric 1) from 4.4.4.4 (4.4.4.4)
Origin IGP, localpref 100, valid, external
Rx pathid: 0, tx pathid: 0
Refresh Epoch 1
twenty-three
2.2.2.2 (metric 1) from 2.2.2.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, external, best
Rx pathid: 0, tx pathid: 0x0
R1#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 5
Paths: (2 available, best # 2, table default)
Advertised to update-groups:
eighteen
Refresh Epoch 1
twenty-three
4.4.4.4 (metric 1) from 4.4.4.4 (4.4.4.4)
Origin IGP, metric 0, localpref 100, valid, external
Rx pathid: 0, tx pathid: 0
Refresh Epoch 1
twenty-three
2.2.2.2 (metric 1) from 2.2.2.2 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
Rx pathid: 0, tx pathid: 0x0
Origin is all IGP. Modify the bgp origin-clde property to make the 22.2.2.2 of R1 to R2 go permanently from R4 to 44.4.4.4 of R4.
Configure on R1:
Step 1: configure prefix-list
Ip prefix-list 22 seq 5 permit 22.2.2.2/32
Ip prefix-list 44 seq 5 permit 44.4.4.4/32
Step 2: configure route-map
Route-map ori-r2 permit 10
Match ip address prefix-list 22
Set origin incomplete
Route-map ori-r2 permit 20
Route-map ori-r4 permit 10
Match ip address prefix-list 44
Set origin incomplete
Route-map ori-r4 permit 20
Step 3: in BGP, call route-map in the corresponding neighbor in direction.
Neighbor 2.2.2.2 route-map ori-r2 in
Neighbor 4.4.4.4 route-map ori-r4 in
Step 4: reset BGP neighbors and relearn routing
Clea ip bgp *
View the R1 BGP routing table:
R1#sh ip bgp
BGP table version is 16, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, I-internal
R RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter
X best-external, an additional-path, c RIB-compressed
Origin codes: I-IGP, e-EGP,?-incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
* > 1.1.1.1 Compact 32 0.0.0.0 0 32768 I
R 2.2.2.2/32 4.4.4.4 0 23 i
R > 2.2.2.2 0 023 I
R 4.4.4.4/32 4.4.4.4 0 0 23 i
R > 2.2.2.2 0 23 I
* > 11.1.1.1 Compact 32 0.0.0.0 0 32768 I
* > 22.2.2.2Compact 32 4.4.4.4 0 23 I
* 2.2.2.2 0 023?
* 44.4.4.4Compact 32 4.4.4.4 0 023?
* > 2.2.2.2 0 23 I
This is, the BGP table shows the 22.2.2.2 routes learned from R2, and the origin-code attribute has been changed to? (incomplete), the 44.4.4.4 route learned from R4, the attribute is also changed to? (incomplete), give priority to routes with an origin-clde of I.
IGP (I) is better than EGP (e) and incomplete (?) The route of the.
R1#sh ip bgp 22.2.2.2
BGP routing table entry for 22.2.2.2/32, version 16
Paths: (2 available, best # 1, table default)
Advertised to update-groups:
eighteen
Refresh Epoch 1
twenty-three
4.4.4.4 (metric 1) from 4.4.4.4 (4.4.4.4)
Origin IGP, localpref 100, valid, external, best
Rx pathid: 0, tx pathid: 0x0
Refresh Epoch 1
twenty-three
2.2.2.2 (metric 1) from 2.2.2.2 (2.2.2.2)
Origin incomplete, metric 0, localpref 100, valid, external
Rx pathid: 0, tx pathid: 0
R1#sh ip bgp 44.4.4.4
BGP routing table entry for 44.4.4.4/32, version 15
Paths: (2 available, best # 2, table default)
Advertised to update-groups:
eighteen
Refresh Epoch 1
twenty-three
4.4.4.4 (metric 1) from 4.4.4.4 (4.4.4.4)
Origin incomplete, metric 0, localpref 100, valid, external
Rx pathid: 0, tx pathid: 0
Refresh Epoch 1
twenty-three
2.2.2.2 (metric 1) from 2.2.2.2 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
Rx pathid: 0, tx pathid: 0x0
The experiment is complete.
