5-2-1. Cisco dual BGP with Community string-HSRP (Load-sharing)

   April 9, 2008
BGP sample configuration 5-1-1

Cisco dual BGP with Community string-HSRP (Load-sharing)

   
  • ISPs : 1
  • WAN links : 2
  • CPE : 2
  • 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 : 10.20.2.0/30 (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 5-1-1

 [Traffic flow]

Outbound traffic on CPE

In this sample, customer is not receiving any BGP route table from ISP. We configured static route points to serial link. Using two HSRP, outbound traffic of IP block 100.100.100.0/24 will be routed to uplink of CPE_1 and traffic of IP block 200.200.200.0/24 will be routed to uplink of CPE_2.

Inbound traffic  on CPE

All inbound traffic associated with 100.100.100.0/24 will be routed thru WAN link of CPE_1 and 200.200.200.0/24 will be routed thru the WAN link of CPE_2. This configuration will cover failover situation and achieve load-sharing plan. One of line failed, other link will take both traffic by sending community strings. See below example and testing output.

topology_BGP5

[CPE_1/Customer Cisco Router]

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CPE_1
!
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
 no ip address
 load-interval 30
 shutdown
 serial restart-delay 0
!
interface Serial1/3
 no ip address
 shutdown
 serial restart-delay 0
!
interface FastEthernet2/0
 ip address 200.200.200.2 255.255.255.0 secondary
 ip address 100.100.100.2 255.255.255.0
 duplex auto
 speed auto
 standby 100 ip 100.100.100.1 <——— HSRP for IP block 100.100.100.0/24
 standby 100 preempt
 standby 100 track Serial1/1 50 <——— When Serial1/1 down, deduct 50 from Priority value
 standby 200 ip 200.200.200.1 <——— HSRP for IP block 200.200.200.0/24
 standby 200 priority 80 <———— Set lower priority for standby path
 standby 200 preempt
!
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
 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 route-to-ISP 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
!
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
ip prefix-list to-ISP seq 10 permit 200.200.200.0/24
!
route-map route-to-ISP permit 10 <——– To control inbound traffic
 match ip address prefix-list prefix-2
 set community 20:3
!
route-map route-to-ISP permit 20
!
control-plane
!
line con 0
 exec-timeout 0 0
 logging synchronous
line aux 0
line vty 0 4
 login
!
end

[CPE_2/Customer Cisco Router]

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CPE_2
!
ip cef
no ip domain lookup
!
interface FastEthernet0/0
 ip address 200.200.200.4 255.255.255.0
 shutdown
 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 10.20.2.1 255.255.255.252
 load-interval 30
 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
!
interface FastEthernet2/0
 ip address 200.200.200.3 255.255.255.0 secondary
 ip address 100.100.100.3 255.255.255.0
 duplex auto
 speed auto
 standby 100 ip 100.100.100.1 <——— HSRP for IP block 100.100.100.0/24
 standby 100 priority 80 <———— Set lower priority for standby path
 standby 100 preempt
 standby 200 ip 200.200.200.1 <——— HSRP for IP block 200.200.200.0/24
 standby 200 preempt
 standby 200 track Serial1/1 50 <——— When Serial1/1 down, deduct 50 from Priority value
!
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 10.20.2.2 remote-as 20 <—————— BGP neighbor to ISP
 neighbor 10.20.2.2 send-community <————– Must configure to send community string
 neighbor 10.20.2.2 prefix-list to-ISP out <——— Allow only IP block need to be advertised to ISP
 neighbor 10.20.2.2 route-map route-to-ISP 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
!
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
ip prefix-list to-ISP seq 10 permit 200.200.200.0/24
!
route-map route-to-ISP permit 10 <——– To control inbound traffic
 match ip address prefix-list prefix-1
 set community 20:3
!
route-map route-to-ISP permit 20
!
control-plane
!
line con 0
 exec-timeout 0 0
 logging synchronous
line aux 0
line vty 0 4
 login
!
end

[PE_1 / ISP Cisco Router]

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname PE_1
!
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 20.1.3.1 255.255.255.252
 serial restart-delay 0
!
interface Serial1/2
 ip address 20.1.4.1 255.255.255.252
 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 20.1.3.2 remote-as 20
 neighbor 20.1.4.2 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 4 permit 20:80
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 20
!
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

[PE_2 / ISP Cisco Router]

version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname PE_2
!
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 10.20.2.2 255.255.255.252
 serial restart-delay 0
!
interface Serial1/1
 ip address 20.2.4.1 255.255.255.252
 serial restart-delay 0
!
interface Serial1/2
 ip address 20.2.3.1 255.255.255.252
 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 10.20.2.1 remote-as 10 <—————— BGP neighbor to Customer
 neighbor 10.20.2.1 route-map customer-in in <—— To apply BGP community policy on customer’s routes
 neighbor 10.20.2.1 route-map no-routes out <——- No BGP routes will be sent to Customer
 neighbor 20.2.3.2 remote-as 20
 neighbor 20.2.4.2 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 4 permit 20:80
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 20
!
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_1#sh standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp Prio P State    Active          Standby         Virtual IP
Fa2/0       100 100  P Active   local           100.100.100.3   100.100.100.1
Fa2/0       200 80   P Standby  100.100.100.3   local           200.200.200.1

CPE_1#sh ip bgp nei 10.20.1.2 ro
Total number of prefixes 0

CPE_1#sh ip bgp nei 10.20.1.2 ad
BGP table version is 6, local router ID is 100.100.100.2
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 i
*> 200.200.200.0    0.0.0.0                  0         32768 i

Total number of prefixes 2

CPE_2#sh standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp Prio P State    Active          Standby         Virtual IP
Fa2/0       100 80   P Standby  100.100.100.2   local           100.100.100.1
Fa2/0       200 100  P Active   local           100.100.100.2   200.200.200.1

CPE_2#sh ip bgp nei 10.20.2.2 ro
Total number of prefixes 0

CPE_2#sh ip bgp nei 10.20.2.2 ad
BGP table version is 6, local router ID is 100.100.100.3
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 i
*> 200.200.200.0    0.0.0.0                  0         32768 i

Total number of prefixes 2

PE_1#sh ip bgp nei 10.20.1.1 ro
BGP table version is 21, local router ID is 20.1.4.1
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
*> 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 20 10 i

Total number of prefixes 2
PE_1#

PE_2#sh ip bgp nei 10.20.2.1 ro
BGP table version is 27, local router ID is 20.2.4.1
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
*> 100.100.100.0/24 10.20.2.1                0             0 20 20 20 10 i
*> 200.200.200.0    10.20.2.1                0             0 10 i

Total number of prefixes 2
PE_2#

TR_A#sh ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 36
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  20 20 20 10
    10.20.2.1 from 20.2.3.1 (20.2.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal
  10
    10.20.1.1 from 20.1.3.1 (20.1.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best

TR_A#sh ip bgp 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 40
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  10
    10.20.2.1 from 20.2.3.1 (20.2.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best
  20 20 20 10
    10.20.1.1 from 20.1.3.1 (20.1.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal
TR_A#

TR_B#sh ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 39
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  20 20 20 10
    10.20.2.1 from 20.2.4.1 (20.2.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal
  10
    10.20.1.1 from 20.1.4.1 (20.1.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best

TR_B#sh ip bgp 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 43
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  10
    10.20.2.1 from 20.2.4.1 (20.2.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal, best
  20 20 20 10
    10.20.1.1 from 20.1.4.1 (20.1.4.1)
      Origin IGP, metric 0, localpref 100, valid, internal
TR_B#

Internet#sh ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 25
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  20 10
    20.50.1.1 from 20.50.1.1 (20.50.1.1)
      Origin IGP, localpref 100, valid, external
  20 10
    20.50.2.1 from 20.50.2.1 (20.50.2.1)
      Origin IGP, localpref 100, valid, external, best

Internet#tr 100.100.100.4
Type escape sequence to abort.
Tracing the route to 100.100.100.4

  1 20.50.2.1 52 msec 52 msec 32 msec
  2 20.1.4.1 [AS 20] 16 msec 68 msec 24 msec
  3 10.20.1.1 [AS 20] 16 msec 52 msec 52 msec
  4 100.100.100.4 [AS 10] 16 msec 64 msec *

Internet#sh ip bgp 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 30
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Advertised to update-groups:
     1
  20 10
    20.50.1.1 from 20.50.1.1 (20.50.1.1)
      Origin IGP, localpref 100, valid, external, best
  20 10
    20.50.2.1 from 20.50.2.1 (20.50.2.1)
      Origin IGP, localpref 100, valid, external

Internet#tr 200.200.200.4
Type escape sequence to abort.
Tracing the route to 200.200.200.4

  1 20.50.1.1 76 msec 60 msec 20 msec
  2 20.2.3.1 [AS 20] 20 msec 92 msec 52 msec
  3 10.20.2.1 [AS 20] 28 msec 76 msec 28 msec
  4 200.200.200.4 [AS 10] 20 msec 48 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 [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.

Author: Chris Yoon

IT professional