The document provides instructions for configuring BGP route aggregation on a network topology. It assigns IP addresses to routers, configures eBGP peering between autonomous systems, and verifies connectivity. It then demonstrates aggregating routes on R2 using the aggregate-address command with different options to summarize routes advertised to neighboring ASes. This reduces the number of routes and optimizes routing table sizes.

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BGP Route Aggregation
LAB WORKBOOK
Prepared By
Sai Linn Thu

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R5
R6
R1
R3
R4
R2
Fa0/0
Fa0/0
Fa1/0 Fa1/0 Fa1/0
Fa1/0
Fa1/0
Fa2/0
Fa3/0
Fa4/0

3. ©2016 RHC Technologies
Step 1 – IP Address Assignment
R1
(
AS
100
)
R2
(
AS
200
)
R3
(
AS
300
)
R4
(
AS
400
)
configure terminal
int F0/0
ip add 10.1.12.1 255.255.255.0
!
configure terminal
int F0/0
ip add 10.1.12.2 255.255.255.0
int F1/0
ip add 10.1.23.2 255.255.255.0
int F2/0
ip add 10.1.24.2 255.255.255.0
int F3/0
ip add 10.1.25.2 255.255.255.0
int F4/0
ip add 10.1.26.2 255.255.255.0
!
configure terminal
int F1/0
ip add 10.1.23.3 255.255.255.0
!
int lo0
ip add 192.168.0.1 255.255.255.0
int lo1
ip add 192.168.1.1 255.255.255.0
int lo2
ip add 192.168.2.1 255.255.255.0
!
configure terminal
int F1/0
ip add 10.1.24.4 255.255.255.0
!
int lo0
ip add 192.168.3.1 255.255.255.0
int lo1
ip add 192.168.4.1 255.255.255.0
int lo2
ip add 192.168.5.1 255.255.255.0
!
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R5
(
AS
500
)
R6
(
AS
600
)
configure terminal
int F1/0
ip add 10.1.25.5 255.255.255.0
!
int lo0
ip add 192.168.6.1 255.255.255.0
int lo1
ip add 192.168.7.1 255.255.255.0
int lo2
ip add 192.168.8.1 255.255.255.0
!
configure terminal
int F1/0
ip add 10.1.26.6 255.255.255.0
!
int lo0
ip add 192.168.9.1 255.255.255.0
int lo1
ip add 192.168.10.1 255.255.255.0
int lo2
ip add 192.168.11.1 255.255.255.0
!

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Step 2 – Configure eBGP
R1
(
AS
100
)
R2
(
AS
200
)
configure terminal
router bgp 100
nei 10.1.12.2 remote-as 200
!
configure terminal
router bgp 200
nei 10.1.12.1 remote-as 100
nei 10.1.23.3 remote-as 300
nei 10.1.24.4 remote-as 400
nei 10.1.25.5 remote-as 500
nei 10.1.26.6 remote-as 600
!
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R5
(
AS
500
)
R6
(
AS
600
)
router bgp 500
nei 10.1.25.2 remote-as 200
net 192.168.6.0 mask 255.255.255.0
net 192.168.7.0 mask 255.255.255.0
net 192.168.8.0 mask 255.255.255.0
!
router bgp 600
nei 10.1.26.2 remote-as 200
net 192.168.9.0 mask 255.255.255.0
net 192.168.10.0 mask 255.255.255.0
net 192.168.11.0 mask 255.255.255.0
!
R3
(
AS
300
)
R4
(
AS
400
)
router bgp 300
nei 10.1.23.2 remote-as 200
net 192.168.0.0 mask 255.255.255.0
net 192.168.1.0 mask 255.255.255.0
net 192.168.2.0 mask 255.255.255.0
!
router bgp 400
nei 10.1.24.2 remote-as 200
net 192.168.3.0 mask 255.255.255.0
net 192.168.4.0 mask 255.255.255.0
net 192.168.5.0 mask 255.255.255.0
!

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Step 2 – eBGP Verification ( R2 )
R2
(
AS
200
)
R2#sh ip bgp summary
BGP router identifier 10.1.26.2, local AS number 200
BGP table version is 13, main routing table version 13
12 network entries using 1776 bytes of memory
12 path entries using 768 bytes of memory
4/4 BGP path/bestpath attribute entries using 544 bytes of memory
4 BGP AS-PATH entries using 96 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 3184 total bytes of memory
BGP activity 12/0 prefixes, 12/0 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.12.1 4 100 4 8 13 0 0 00:00:37 0
10.1.23.3 4 300 5 8 13 0 0 00:01:15 3
10.1.24.4 4 400 5 8 13 0 0 00:01:14 3
10.1.25.5 4 500 5 8 13 0 0 00:01:01 3
10.1.26.6 4 600 5 8 13 0 0 00:01:06 3
R2#
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Step 2 – BGP Table Verification ( R2 )
R2
(
AS
200
)
R2#show ip bgp
BGP table version is 13, local router ID is 10.1.26.2
Network Next Hop Metric LocPrf Weight Path
*> 192.168.0.0 10.1.23.3 0 0 300 i
*> 192.168.1.0 10.1.23.3 0 0 300 i
*> 192.168.2.0 10.1.23.3 0 0 300 i
*> 192.168.3.0 10.1.24.4 0 0 400 i
*> 192.168.4.0 10.1.24.4 0 0 400 i
*> 192.168.5.0 10.1.24.4 0 0 400 i
*> 192.168.6.0 10.1.25.5 0 0 500 i
*> 192.168.7.0 10.1.25.5 0 0 500 i
*> 192.168.8.0 10.1.25.5 0 0 500 i
*> 192.168.9.0 10.1.26.6 0 0 600 i
*> 192.168.10.0 10.1.26.6 0 0 600 i
*> 192.168.11.0 10.1.26.6 0 0 600 i
R2#
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Step 3 – Aggregate & Analyze ( R2 )
R2
(
AS
200
)
router bgp 200
aggregate-address 192.168.0.0 255.255.240.0
!
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R2 ( AS 200 )
R2#show ip bgp
BGP table version is 16, local router ID is 10.1.26.2
Network Next Hop Metric LocPrf Weight Path
*> 192.168.0.0 10.1.23.3 0 0 300 i
*> 192.168.0.0/20 0.0.0.0 32768 i
*> 192.168.1.0 10.1.23.3 0 0 300 i
*> 192.168.2.0 10.1.23.3 0 0 300 i
*> 192.168.3.0 10.1.24.4 0 0 400 i
*> 192.168.4.0 10.1.24.4 0 0 400 i
*> 192.168.5.0 10.1.24.4 0 0 400 i
*> 192.168.6.0 10.1.25.5 0 0 500 i
*> 192.168.7.0 10.1.25.5 0 0 500 i
*> 192.168.8.0 10.1.25.5 0 0 500 i
*> 192.168.9.0 10.1.26.6 0 0 600 i
*> 192.168.10.0 10.1.26.6 0 0 600 i
*> 192.168.11.0 10.1.26.6 0 0 600 i
R2#

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Step 3 – Analyze BGP Table ( R1 )
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R1 ( AS 100 )
R1#show ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 192.168.0.0 10.1.12.2 0 200 300 i
*> 192.168.0.0/20 10.1.12.2 0 0 200 i
*> 192.168.1.0 10.1.12.2 0 200 300 i
*> 192.168.2.0 10.1.12.2 0 200 300 i
*> 192.168.3.0 10.1.12.2 0 200 400 i
*> 192.168.4.0 10.1.12.2 0 200 400 i
*> 192.168.5.0 10.1.12.2 0 200 400 i
*> 192.168.6.0 10.1.12.2 0 200 500 i
*> 192.168.7.0 10.1.12.2 0 200 500 i
*> 192.168.8.0 10.1.12.2 0 200 500 i
*> 192.168.9.0 10.1.12.2 0 200 600 i
*> 192.168.10.0 10.1.12.2 0 200 600 i
*> 192.168.11.0 10.1.12.2 0 200 600 i
R1#

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Step 4 – Aggregate summary-only & Analyze ( R2 )
R2
(
AS
200
)
router bgp 200
aggregate-address 192.168.0.0 255.255.240.0 summary-only
!
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R2 ( AS 200 )
R2#show ip bgp
BGP table version is 28, local router ID is 10.1.26.2
Status codes: s suppressed
Network Next Hop Metric LocPrf Weight Path
s> 192.168.0.0 10.1.23.3 0 0 300 i
*> 192.168.0.0/20 0.0.0.0 32768 i
s> 192.168.1.0 10.1.23.3 0 0 300 i
s> 192.168.2.0 10.1.23.3 0 0 300 i
s> 192.168.3.0 10.1.24.4 0 0 400 i
s> 192.168.4.0 10.1.24.4 0 0 400 i
s> 192.168.5.0 10.1.24.4 0 0 400 i
s> 192.168.6.0 10.1.25.5 0 0 500 i
s> 192.168.7.0 10.1.25.5 0 0 500 i
s> 192.168.8.0 10.1.25.5 0 0 500 i
s> 192.168.9.0 10.1.26.6 0 0 600 i
s> 192.168.10.0 10.1.26.6 0 0 600 i
s> 192.168.11.0 10.1.26.6 0 0 600 i
R2#

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Step 4 – Analyze BGP Table & Routing Table ( R1 )
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R1 ( AS 100 )
R1#show ip bgp
BGP table version is 28, local router ID is 10.1.12.1
Network Next Hop Metric LocPrf Weight Path
*> 192.168.0.0/20 10.1.12.2 0 0 200 i
R1#
R1 ( AS 100 )
R1#show ip route bgp
B 192.168.0.0/20 [20/0] via 10.1.12.2, 00:21:22
R1#
R1 ( AS 100 )
R1#sh ip bgp 192.168.0.0/20
BGP routing table entry for 192.168.0.0/20, version 16
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
200, (aggregated by 200 10.1.26.2)
10.1.12.2 from 10.1.12.2 (10.1.26.2)
Origin IGP, metric 0, localpref 100, valid, external, atomic-aggregate, best
R1#

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Step 5 – Generate as-set path information ( R2 )
R2 ( AS 200 )
router bgp 200
aggregate-address 192.168.0.0 255.255.240.0 summary-only as-set
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R2 ( AS 200 )
R2#show ip bgp
BGP table version is 29, local router ID is 10.1.26.2
Network Next Hop Metric LocPrf Weight Path
s> 192.168.0.0 10.1.23.3 0 0 300 i
*> 192.168.0.0/20 0.0.0.0 100 32768 {300,400,500,600} i
s> 192.168.1.0 10.1.23.3 0 0 300 i
s> 192.168.2.0 10.1.23.3 0 0 300 i
s> 192.168.3.0 10.1.24.4 0 0 400 i
s> 192.168.4.0 10.1.24.4 0 0 400 i
s> 192.168.5.0 10.1.24.4 0 0 400 i
s> 192.168.6.0 10.1.25.5 0 0 500 i
s> 192.168.7.0 10.1.25.5 0 0 500 i
s> 192.168.8.0 10.1.25.5 0 0 500 i
s> 192.168.9.0 10.1.26.6 0 0 600 i
s> 192.168.10.0 10.1.26.6 0 0 600 i
s> 192.168.11.0 10.1.26.6 0 0 600 i
R2#

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Step 5 – Analyze BGP Table & Routing Table ( R1 )
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R1 ( AS 100 )
R1#show ip bgp
BGP table version is 29, local router ID is 10.1.12.1
Network Next Hop Metric LocPrf Weight Path
*> 192.168.0.0/20 10.1.12.2 0 0 200 {300,400,500,600} i
R1 ( AS 100 )
R1#show ip route bgp
B 192.168.0.0/20 [20/0] via 10.1.12.2, 00:21:22
R1#
R1 ( AS 100 )
R1#show ip bgp 192.168.0.0/20
BGP routing table entry for 192.168.0.0/20, version 29
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
200 {300,400,500,600}, (aggregated by 200 10.1.26.2)
10.1.12.2 from 10.1.12.2 (10.1.26.2)
Origin IGP, metric 0, localpref 100, valid, external, best
R1#

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