Cisco dual BGP with Origin Value (Load-balancing)
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[Read it first]
When you have more than two ISP links, Origin attribute option won’t be enough to achieve failover and load-sharing goals.why? simply shortest AS path is more prefer attribute than Origin attribute option on BGP selection criteria.Below example we used AS-Path prepending for inbound traffic on shadow link which is connected to ISP_"B".
[Traffic flow]
Configured static routes pointing to both Serial links, due to default route thru BGP cannot support load-sharing. It wouldn’t be 50/50 traffic sharing, 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.
[CPE/Customer Cisco Router]
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CPE
!
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
redistribute connected
neighbor 10.20.1.2 remote-as 20 <—————— BGP neighbor to ISP_"A"
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
neighbor 10.30.1.2 remote-as 30 <—————— BGP neighbor to ISP_"B"
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
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
ip route 0.0.0.0 0.0.0.0 Serial1/2
!
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
ip prefix-list to-ISP seq 10 permit 200.200.200.0/24
!
route-map traffic-1 permit 10
match ip address prefix-list prefix-1
set origin igp
!
route-map traffic-1 permit 20
match ip address prefix-list prefix-2
set as-path prepend 10
!
route-map traffic-2 permit 10
match ip address prefix-list prefix-2
set origin igp
!
route-map traffic-2 permit 20
match ip address prefix-list prefix-1
set as-path prepend 10
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
end
[ISP_A PE/ISP Cisco Router]
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP_A
!
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 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
!
route-map no-routes deny 10 <——- No BGP routes will be sent to Customer
!
control-plane
!
line con 0
exec-timeout 0 0
logging synchronous
line aux 0
line vty 0 4
login
!
end
[ISP_B PE / ISP Cisco Router]
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP_B
!
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 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
!
route-map no-routes deny 10 <——- No BGP routes will be sent to Customer
!
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 ad
BGP table version is 11, 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 ?
*> 200.200.200.0 0.0.0.0 0 32768 ?Total number of prefixes 2
CPE#sh ip bgp nei 10.30.1.2 ad
BGP table version is 11, 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 ?
*> 200.200.200.0 0.0.0.0 0 32768 ?Total number of prefixes 2
CPE#ISP_A#sh ip bgp neighbors 10.20.1.1 ro
BGP table version is 28, 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 10 10 ?Total number of prefixes 2
ISP_A#
ISP_A#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 27
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
10
10.20.1.1 from 10.20.1.1 (100.100.100.1)
Origin IGP, metric 0, localpref 100, valid, external, bestISP_A#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 28
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
30 10
20.30.1.2 from 20.20.1.2 (20.50.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
10 10
10.20.1.1 from 10.20.1.1 (100.100.100.1)
Origin incomplete, metric 0, localpref 100, valid, external
ISP_A#ISP_B#sh ip bgp neighbors 10.30.1.1 ro
BGP table version is 29, 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 10 10 ?
*> 200.200.200.0 10.30.1.1 0 0 10 iTotal number of prefixes 2
ISP_B#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 29
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
20 10
20.30.1.1 from 30.30.1.2 (30.50.1.1)
Origin IGP, metric 0, localpref 100, valid, internal, best
10 10
10.30.1.1 from 10.30.1.1 (100.100.100.1)
Origin incomplete, metric 0, localpref 100, valid, external
ISP_B#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 27
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1
10
10.30.1.1 from 10.30.1.1 (100.100.100.1)
Origin IGP, metric 0, localpref 100, valid, external, best
ISP_B#TR_A#sh ip bgp 100.100.100.2
BGP routing table entry for 100.100.100.0/24, version 23
Paths: (1 available, best #1, table Default-IP-Routing-Table)
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, bestTR_A#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 24
Paths: (2 available, best #2, table Default-IP-Routing-Table)
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 27
Paths: (2 available, best #2, table Default-IP-Routing-Table)
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, bestTR_B#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 25
Paths: (1 available, best #1, table Default-IP-Routing-Table)
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 26
Paths: (2 available, best #2, table Default-IP-Routing-Table)
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, bestInternet#tr 100.100.100.2
Type escape sequence to abort.
Tracing the route to 100.100.100.21 20.50.1.1 20 msec 64 msec 4 msec
2 20.20.1.1 [AS 20] 32 msec 284 msec 16 msec
3 10.20.1.1 [AS 20] 16 msec 40 msec 40 msec
4 100.100.100.2 [AS 10] 52 msec 72 msec *Internet#sh ip bgp 200.200.200.2
BGP routing table entry for 200.200.200.0/24, version 27
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 64 msec 44 msec 24 msec
2 30.30.1.1 [AS 30] 20 msec 40 msec 48 msec
3 10.30.1.1 [AS 30] 16 msec 52 msec 48 msec
4 200.200.200.2 [AS 10] 104 msec 92 msec *
Internet#
[Dynamips testing]
Download and test it yourself with below Dynamips configuration files.
Dynamips NET file
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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