| Here is another lab from Cisco Systems regarding route aggregation in BGP, using GNS3: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094826.shtml | ||||||||||||||||||||
 |
| Topology |
!
interface Serial1/0
ip address 2.2.2.2 255.0.0.0
!
serial restart-delay 0
interface Loopback0
ip address 160.20.1.1 255.255.0.0
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 160.20.0.0
!--- Router A advertises network 160.20.0.0/16.
neighbor 2.2.2.1 remote-as 300
no auto-summary
RouterB Configuration:
interface Loopback0
ip address 160.10.1.1 255.255.0.0
!
interface Serial1/0
ip address 3.3.3.3 255.0.0.0
serial restart-delay 0
!
router bgp 200
no synchronization
bgp log-neighbor-changes
network 160.10.0.0
!--- Router B advertises network 160.10.0.0/16.
neighbor 3.3.3.1 remote-as 300
no auto-summary
!
Router C Configuration:
interface Serial1/0ip address 2.2.2.1 255.0.0.0
serial restart-delay 0
!
interface Serial1/1
ip address 3.3.3.1 255.0.0.0
serial restart-delay 0
!
interface Serial1/2
ip address 4.4.4.1 255.0.0.0
serial restart-delay 0
!
router bgp 300
no synchronization
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 100
neighbor 3.3.3.3 remote-as 200
neighbor 4.4.4.4 remote-as 400
no auto-summary
Router D Configuration:
interface Serial1/0ip address 4.4.4.4 255.255.255.0
serial restart-delay 0
!
router bgp 400
no synchronization
bgp log-neighbor-changes
neighbor 4.4.4.1 remote-as 300
no auto-summary
!
The .net file if you want to simulate it using GNS3:
autostart = False
version = 0.8.2-BETA2
[sa1d10dc:7200]
workingdir = D:\Cache\TEMP
udp = 10000
[[3745]]
image = D:\Apps\GNS3\IOS\c3745-adventerprisek9-mz.124-25a\C3745-AD.BIN
idlepc = 0x60aa5f14
sparsemem = True
ghostios = True
[[ROUTER RouterB]]
model = 3745
console = 2002
aux = 2502
cnfg = RouterB.cfg
slot1 = NM-4T
s1/0 = RouterC s1/1
x = 48.0
y = -30.0
z = 1.0
hx = 2.5
hy = -23.0
[[ROUTER RouterC]]
model = 3745
console = 2003
aux = 2503
cnfg = RouterC.cfg
slot1 = NM-4T
s1/0 = RouterA s1/0
s1/1 = RouterB s1/0
s1/2 = RouterD s1/0
x = -109.0
y = -28.0
z = 1.0
[[ROUTER RouterA]]
model = 3745
console = 2001
aux = 2501
cnfg = RouterA.cfg
slot1 = NM-4T
s1/0 = RouterC s1/0
x = -268.0
y = -37.0
z = 1.0
[[ROUTER RouterD]]
model = 3745
console = 2004
aux = 2504
cnfg = RouterD.cfg
slot1 = NM-4T
s1/0 = RouterC s1/2
x = -100.0
y = 143.0
z = 1.0
hx = 1.0
hy = 38.0
[GNS3-DATA]
configs = .
[[NOTE 1]]
text = AS 400
x = -96.0
y = 201.0
z = 2.0
[[NOTE 2]]
text = AS 200
x = 52.0
y = -75.0
z = 2.0
[[NOTE 3]]
text = AS 300
x = -104.0
y = -80.0
z = 2.0
[[NOTE 4]]
text = AS 100
x = -264.0
y = -85.0
z = 2.0
[[NOTE 5]]
text = s1/0
x = 32.533818023
y = -29.4738963195
interface = RouterD s1/0
z = 2.0
[[NOTE 6]]
text = s1/2
x = 42.466181977
y = 43.4738963195
interface = RouterC s1/2
z = 2.0
[[NOTE 7]]
text = s1/0
x = -23.9269011579
y = 34.4171396169
interface = RouterC s1/0
z = 2.0
[[NOTE 8]]
text = s1/1
x = 66.6561983271
y = -21.2331571963
interface = RouterC s1/1
z = 2.0
[[NOTE 9]]
text = s1/0
x = -15.6561983271
y = 34.2331571963
interface = RouterB s1/0
z = 2.0
[[NOTE 10]]
text = s1/0
x = 59.9269011579
y = 29.5828603831
interface = RouterA s1/0
z = 2.0
[[SHAPE 1]]
type = ellipse
x = -145.0
y = 97.0
width = 146.0
height = 160.0
border_style = 2
[[SHAPE 2]]
type = ellipse
x = 15.0
y = -102.0
width = 146.0
height = 160.0
border_style = 2
[[SHAPE 3]]
type = ellipse
x = -148.0
y = -105.0
width = 146.0
height = 160.0
border_style = 2
[[SHAPE 4]]
type = ellipse
x = -315.0
y = -97.0
width = 152.0
height = 154.0
border_style = 2
RouterC without aggregation configured:
RouterC#show ip bgpBGP table version is 3, local router ID is 4.4.4.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 160.10.0.0 3.3.3.3 0 0 200 i
*> 160.20.0.0 2.2.2.2 0 0 100 i
Configuring aggregation in RouterC:
RouterC(config)#router bgp 300RouterC(config-router)#aggregate-address 160.0.0.0 255.0.0.0 summary-only
Router C only announces the aggregate 160.0.0.0/8 to Router D. The aggregate 160.0.0.0/8 is the classless interdomain routing (CIDR) route. The more specific 160.10.0.0/16 and 160.20.0.0/16 routes are suppressed, as this BGP table on Router C shows:
RouterC#show ip bgp
BGP table version is 6, local router ID is 4.4.4.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 160.0.0.0/8 0.0.0.0 32768 i
s> 160.10.0.0 3.3.3.3 0 0 200 i
s> 160.20.0.0 2.2.2.2 0 0 100 i
Here is the BGP table of Router D.
The aggregate route 160.0.0.0/8 is considered to have originated from AS-300 with origin code IGP. The route has lost all the specific AS_PATH information of the individual prefixes 160.10.0.0/16, of AS-200, and 160.20.0.0/16, of AS-100.
RouterD#show ip bgp
BGP table version is 6, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 160.0.0.0/8 4.4.4.1 0 0 300 i
