There are multiple ways to achieve your requirement Manoj. I am suggesting my option of having this. Lets consider the below topology,
Config parameters
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 : Default route from ISP's
LAN : ISP_A (AS20), ISP_B(AS30), Customer (AS10) and other ISP (AS50)
Lets begin with the configuration
CPE_1 Config
!
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 100.100.100.1 255.255.255.0
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 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
neighbor 100.100.100.2 remote-as 10 <----------- iBGP neighbor to CPE_2
neighbor 100.100.100.2 default-originate <------- Send default route
neighbor 100.100.100.2 route-map route-to-ibgp in <------- Make less prefer
no auto-summary
!
ip http server
no ip http secure-server
ip forward-protocol nd
!
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 as-path prepend 10 10 10
!
route-map route-to-ISP permit 20
!
route-map route-to-ibgp permit 10 <------- Make less prefer
set local-preference 80
CPE_2 Config
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 10.30.1.1 255.255.255.252
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 100.100.100.2 255.255.255.0 secondary
ip address 200.200.200.1 255.255.255.0
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 10.30.1.2 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 route-to-ISP out <-------- To control inbound traffic
neighbor 100.100.100.1 remote-as 10 <----------- iBGP neighbor to CPE_1
neighbor 100.100.100.1 default-originate <------- Send default route
neighbor 100.100.100.1 route-map route-to-ibgp in <------- Make less prefer
no auto-summary
!
ip http server
no ip http secure-server
ip forward-protocol nd
!
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 as-path prepend 10 10 10
!
route-map route-to-ISP permit 20
!
route-map route-to-ibgp permit 10 <------- Make less prefer
set local-preference 80
ISP_A PE Router
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 default-originate
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
ISP_B PE Configs
!
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 default-originate
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
Now let's verify our requirement was achieved
CPE_1#sh ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 21
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
20
10.20.1.2 from 10.20.1.2 (20.20.1.1)
Origin IGP, metric 0, localpref 100, valid, external, best
Local
100.100.100.2 from 100.100.100.2 (200.200.200.1)
Origin IGP, metric 0, localpref 80, valid, internal
CPE_1#sh ip bgp nei 10.20.1.2 ad
BGP table version is 23, 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 i
*> 200.200.200.0 0.0.0.0 0 32768 i
Total number of prefixes 2
CPE_1#
CPE_2#sh ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 20
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
30
10.30.1.2 from 10.30.1.2 (30.30.1.1)
Origin IGP, metric 0, localpref 100, valid, external, best
Local
100.100.100.1 from 100.100.100.1 (100.100.100.1)
Origin IGP, metric 0, localpref 80, valid, internal
CPE_2#sh ip bgp nei 10.30.1.2 ad
BGP table version is 20, local router ID is 200.200.200.1
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 i
*> 200.200.200.0 0.0.0.0 0 32768 i
Total number of prefixes 2
CPE_2#
ISP_A#sh ip bgp nei 10.20.1.1 ro
BGP table version is 56, 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 10 10 i
Total number of prefixes 2
ISP_A#
ISP_B#sh ip bgp nei 10.30.1.1 ro
BGP table version is 60, 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 10 10 i
*> 200.200.200.0 10.30.1.1 0 0 10 i
Total number of prefixes 2
ISP_B#
TR_A#sh ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 51
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 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 58
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 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 61
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 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 66
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#
Other_ISP#sh ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 64
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
30 20 10
30.50.1.1 from 30.50.1.1 (30.50.1.1)
Origin IGP, localpref 100, valid, external
Other_ISP#tr 100.100.100.3
Type escape sequence to abort.
Tracing the route to 100.100.100.3
1 20.50.1.1 64 msec 28 msec 8 msec
2 20.20.1.1 [AS 20] 40 msec 24 msec 4 msec
3 10.20.1.1 [AS 20] 16 msec 20 msec 8 msec
4 100.100.100.3 [AS 10] 44 msec * 40 msec
Other_ISP#sh ip bgp 200.200.200.0
BGP routing table entry for 200.200.200.0/24, version 71
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
Other_ISP#tr 200.200.200.3
Type escape sequence to abort.
Tracing the route to 200.200.200.3
1 30.50.1.1 52 msec 64 msec 12 msec
2 30.30.1.1 [AS 30] 16 msec 20 msec 8 msec
3 10.30.1.1 [AS 30] 12 msec 32 msec 16 msec
4 200.200.200.3 [AS 10] 20 msec * 44 msec
Other_ISP#
Hope this helps.
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