Cisco dual BGP with Community string (Load-balancing)
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[Traffic flow]
Outbound traffic on CPE
In this sample, customer is not receiving any BGP route table from ISP. We configured static routes are pointing to both serial links. Of cause it wouldn’t be 50/50, due to packets will be routed by destination based.
All traffic associated with 100.100.100.0/24 will be routed thru ISP_"A" and 200.200.200.0/24 will be routed thru ISP_"B". This configuration will cover failover situation as well. One of line failed, other link will take both traffic. See below example and testing output.
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CPE
!
boot-start-marker
boot-end-marker
!
ip cef
no ip domain lookup
!
interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
ip address 10.20.1.1 255.255.255.252
load-interval 30
serial restart-delay 0
!
interface Serial1/2
ip address 10.30.1.1 255.255.255.252
load-interval 30
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
interface FastEthernet2/0
ip address 200.200.200.1 255.255.255.0 secondary
ip address 100.100.100.1 255.255.255.0
duplex auto
speed auto
!
router bgp 10
no synchronization
bgp log-neighbor-changes
network 100.100.100.0 mask 255.255.255.0
network 200.200.200.0
redistribute connected
neighbor 10.20.1.2 remote-as 20 <—————— BGP neighbor to ISP_"A"
neighbor 10.20.1.2 send-community <————– Must configure to send community string
neighbor 10.20.1.2 prefix-list to-ISP out <——— Allow only IP block need to be advertised to ISP
neighbor 10.20.1.2 route-map traffic-1 out <—- To control inbound traffic
neighbor 10.30.1.2 remote-as 30 <—————— BGP neighbor to ISP_"B"
neighbor 10.30.1.2 send-community <————– Must configure to send community string
neighbor 10.30.1.2 prefix-list to-ISP out <——— Allow only IP block need to be advertised to ISP
neighbor 10.30.1.2 route-map traffic-2 out <—- To control inbound traffic
no auto-summary
!
ip http server
no ip http secure-server
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 Serial1/1 <————– To control outbound traffic, load-sharing
ip route 0.0.0.0 0.0.0.0 Serial1/2 <————– To control outbound traffic, load-sharing
!
ip bgp-community new-format <————– For new BGP community format
!
ip prefix-list prefix-1 seq 5 permit 100.100.100.0/24
!
ip prefix-list prefix-2 seq 5 permit 200.200.200.0/24
!
ip prefix-list to-ISP seq 5 permit 100.100.100.0/24 <——- Permitting IP blocks for advertisement
ip prefix-list to-ISP seq 10 permit 200.200.200.0/24 <—– Permitting IP blocks for advertisement
!
route-map traffic-1 permit 10 <——— Route-map to control inbound traffic
match ip address prefix-list prefix-2
set community 20:3
!
route-map traffic-1 permit 20
!
route-map traffic-2 permit 10 <——— Route-map to control inbound traffic
match ip address prefix-list prefix-1
set community 30:3
!
route-map traffic-2 permit 20
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
end
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP_A
!
boot-start-marker
boot-end-marker
!
ip cef
no ip domain lookup
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
ip address 10.20.1.2 255.255.255.252
serial restart-delay 0
!
interface Serial1/1
ip address 20.20.1.1 255.255.255.252
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
router bgp 20
no synchronization
bgp log-neighbor-changes
redistribute connected
neighbor 10.20.1.1 remote-as 10 <—————— BGP neighbor to Customer
neighbor 10.20.1.1 route-map customer-in in <—— To apply BGP community policy on customer’s routes
neighbor 10.20.1.1 route-map no-routes out <——- No BGP routes will be sent to Customer
neighbor 20.20.1.2 remote-as 20
no auto-summary
!
ip http server
no ip http secure-server
ip forward-protocol nd
!
ip bgp-community new-format <————– For new BGP community format
ip community-list 1 permit 20:1
ip community-list 2 permit 20:2
ip community-list 3 permit 20:3
ip community-list 5 permit 20:120
!
route-map no-routes deny 10
!
route-map customer-in permit 10
match community 1
set as-path prepend 20
!
route-map customer-in permit 20
match community 2
set as-path prepend 20 20
!
route-map customer-in permit 30
match community 3
set as-path prepend 20 20 30
!
route-map customer-in permit 40
match community 4
set local-preference 80
!
route-map customer-in permit 50
match community 5
set local-preference 120
!
route-map customer-in permit 60
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
end
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP_B
!
boot-start-marker
boot-end-marker
!
ip cef
no ip domain lookup
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
ip address 10.30.1.2 255.255.255.252
serial restart-delay 0
!
interface Serial1/1
ip address 30.30.1.1 255.255.255.252
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
router bgp 30
no synchronization
bgp log-neighbor-changes
redistribute connected
neighbor 10.30.1.1 remote-as 10 <—————— BGP neighbor to Customer
neighbor 10.30.1.1 route-map customer-in in <—— To apply BGP community policy on customer’s route
neighbor 10.30.1.1 route-map no-routes out <——- No BGP routes will be sent to Customer
neighbor 30.30.1.2 remote-as 30
no auto-summary
!
ip http server
no ip http secure-server
ip forward-protocol nd
!
ip bgp-community new-format <————– For new BGP community format
ip community-list 1 permit 30:1
ip community-list 2 permit 30:2
ip community-list 3 permit 30:3
ip community-list 4 permit 30:80
ip community-list 5 permit 30:120
!
route-map no-routes deny 10
!
route-map customer-in permit 10
match community 1
set as-path prepend 30
!
route-map customer-in permit 20
match community 2
set as-path prepend 30 30
!
route-map customer-in permit 30
match community 3
set as-path prepend 30 30 30
!
route-map customer-in permit 40
match community 4
set local-preference 80
!
route-map customer-in permit 50
match community 5
set local-preference 120
!
route-map customer-in permit 60
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
end
[Verifing output]
CPE#sh ip bgp nei 10.20.1.2 ro
Total number of prefixes 0
CPE#sh ip bgp nei 10.20.1.2 ad
BGP table version is 5, local router ID is 100.100.100.1
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal,
r RIB-failure, S Stale
Origin codes: i – IGP, e – EGP, ? – incompleteNetwork Next Hop Metric LocPrf Weight Path
*> 100.100.100.0/24 0.0.0.0 0 32768 i
*> 200.200.200.0 0.0.0.0 0 32768 iTotal number of prefixes 2
CPE#sh ip bgp nei 10.30.1.2 ro
Total number of prefixes 0CPE#sh ip bgp nei 10.30.1.2 ad
BGP table version is 5, local router ID is 100.100.100.1
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal,
r RIB-failure, S Stale
Origin codes: i – IGP, e – EGP, ? – incompleteNetwork Next Hop Metric LocPrf Weight Path
*> 100.100.100.0/24 0.0.0.0 0 32768 i
*> 200.200.200.0 0.0.0.0 0 32768 iTotal number of prefixes 2
CPE#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "static", distance 1, metric 0 (connected), candidate default path
Routing Descriptor Blocks:
* directly connected, via Serial1/1
Route metric is 0, traffic share count is 1
directly connected, via Serial1/2
Route metric is 0, traffic share count is 1CPE#
ISP_A#sh ip bgp nei 10.20.1.1 ro
BGP table version is 16, local router ID is 20.20.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal,
r RIB-failure, S Stale
Origin codes: i – IGP, e – EGP, ? – incompleteNetwork Next Hop Metric LocPrf Weight Path
*> 100.100.100.0/24 10.20.1.1 0 0 10 i
* 200.200.200.0 10.20.1.1 0 0 20 20 30 10 iTotal number of prefixes 2
ISP_A#
ISP_B#sh ip bgp nei 10.30.1.1 ro
BGP table version is 20, local router ID is 30.30.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal,
r RIB-failure, S Stale
Origin codes: i – IGP, e – EGP, ? – incompleteNetwork Next Hop Metric LocPrf Weight Path
* 100.100.100.0/24 10.30.1.1 0 0 30 30 30 10 i
*> 200.200.200.0 10.30.1.1 0 0 10 iTotal number of prefixes 2
ISP_B#
TR_A#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 15
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1
10
10.20.1.1 from 20.20.1.1 (20.20.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
TR_A#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 16
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1 2
50 30 10
20.50.1.2 from 20.50.1.2 (30.50.1.2)
Origin IGP, localpref 100, valid, external
30 10
20.30.1.2 from 20.30.1.2 (30.50.1.1)
Origin IGP, localpref 100, valid, external, best
TR_A#
TR_B#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 19
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1 2
50 20 10
30.50.1.2 from 30.50.1.2 (30.50.1.2)
Origin IGP, localpref 100, valid, external
20 10
20.30.1.1 from 20.30.1.1 (20.50.1.1)
Origin IGP, localpref 100, valid, external, best
TR_B#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 17
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
2
10
10.30.1.1 from 30.30.1.1 (30.30.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
TR_B#
Internet#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 17
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1
30 20 10
30.50.1.1 from 30.50.1.1 (30.50.1.1)
Origin IGP, localpref 100, valid, external
20 10
20.50.1.1 from 20.50.1.1 (20.50.1.1)
Origin IGP, localpref 100, valid, external, best
Internet#tr 100.100.100.2
Type escape sequence to abort.
Tracing the route to 100.100.100.21 20.50.1.1 40 msec 40 msec 28 msec
2 20.20.1.1 [AS 20] 24 msec 36 msec 68 msec
3 10.20.1.1 [AS 20] 16 msec 52 msec 52 msec
4 *
100.100.100.2 [AS 10] 68 msec 104 msecInternet#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 18
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
30 10
30.50.1.1 from 30.50.1.1 (30.50.1.1)
Origin IGP, localpref 100, valid, external, best
20 30 10
20.50.1.1 from 20.50.1.1 (20.50.1.1)
Origin IGP, localpref 100, valid, externalInternet#tr 200.200.200.2
Type escape sequence to abort.
Tracing the route to 200.200.200.21 30.50.1.1 40 msec 52 msec 56 msec
2 30.30.1.1 [AS 30] 28 msec 48 msec 40 msec
3 10.30.1.1 [AS 30] 24 msec 68 msec 36 msec
4 *
200.200.200.2 [AS 10] 84 msec 84 msec
Internet#
[Dynamips testing]
Download and test it yourself with below Dynamips configuration files.
If you have any questions, feel free to send email us at [email protected]. If you are looking for professional grade service, you might want to try our "BGP experts service". What is "BGP Experts service"? Click "BGP Experts" from the top menu option. You will find out what the "BGP Experts" and what we are doing here for.
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