Cisco dual BGP with Community string-HSRP (Load-sharing)
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[Traffic flow]
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.
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.
[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.
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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 200.200.200.1CPE_1#sh ip bgp nei 10.20.1.2 ro
Total number of prefixes 0CPE_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, ? – 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_2#sh standby brief
P indicates configured to preempt.
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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 100.100.100.2 200.200.200.1CPE_2#sh ip bgp nei 10.20.2.2 ro
Total number of prefixes 0CPE_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, ? – 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
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, ? – 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 20 10 iTotal 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, ? – incompleteNetwork 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 iTotal 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, bestTR_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, bestTR_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, bestInternet#tr 100.100.100.4
Type escape sequence to abort.
Tracing the route to 100.100.100.41 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, externalInternet#tr 200.200.200.4
Type escape sequence to abort.
Tracing the route to 200.200.200.41 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.
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