Home BGP Configurations Cisco 4-5-2. Cisco dual BGP with Origin Value (Load-balancing)

Cisco dual BGP with Origin Value (Load-balancing)

   
  • ISPs : 2
  • WAN links : 2
  • CPE : 1
  • PE : 2
  • Device : Cisco router with LAN/WAN ports.
  • WAN1 / Serial IP : 10.20.1.0/30 (mask 255.255.255.252)
  • WAN2 / Serial IP : 10.30.1.0/30 (mask 255.255.255.252)
  • LAN / Ethernet IP : 100.100.100.0/24 and 200.200.200.0/24
  • Receiving Route : No BGP route table from ISP
  • Memory : Full route(recommend 512M), partial route
    (recommend 128-256M), default route only in this sample.
  • LAN : ISP_A (AS20), ISP_B(AS30), Customer (AS10) and other ISP (AS50)

 

BGP sample configuration 3-1-1

[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]

Outbound traffic on CPE

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. 

 
Inbound traffic  on CPE

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.

topology_BGP4-2-1.png

[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
!
en
d

[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, ? - incomplete

   Network          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, ? - incomplete

   Network          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, ? - incomplete

   Network          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, best



ISP_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, ? - incomplete

   Network          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 i

Total 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, best



TR_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, best



TR_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, best



Internet#tr  100.100.100.2

Type escape sequence to abort.
Tracing the route to 100.100.100.2

  1 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, external



Internet#tr 200.200.200.2

Type escape sequence to abort.
Tracing the route to 200.200.200.2

  1 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
  Router configuration files

If you have any questions, feel free to send email us at This e-mail address is being protected from spambots. You need JavaScript enabled to view it . 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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