Aggregate address

[BannerMOTD]

So when i apply an aggregate to an ebgp peer in as 10 for specific prefixes 172.16.2.1/24 and 172.16.3.1/24 I used the aggregate address of 172.16.0.0/22. So the ebgp peer that receives the aggregate sees 172.16.0.0/22 as expected but when i try to ping a specfic prefix such as the ones i mentioned above the router that is the ebgp peer of the as 10 router drops the packet. I even created a static route for the aggregate route on the ibgp router. As 500 is what the router that is ebgp peering with router in as 10 is in. And i have another router in as 500 ibgp peering with the router that is ebgp peering with the router in as 10.

Router in AS 10 <----->Router(EBGP)AS 500 and then iBGP router also in AS 500.

R5#show ip route<---Router in AS 10
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     4.0.0.0/32 is subnetted, 1 subnets
S       4.4.4.4 [1/0] via 55.55.55.2
     55.0.0.0/30 is subnetted, 1 subnets
C       55.55.55.0 is directly connected, Serial2/3
     5.0.0.0/32 is subnetted, 1 subnets
C       5.5.5.5 is directly connected, Loopback0
     172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
B       172.16.0.0/22 [200/0] via 0.0.0.0, 00:51:10, Null0
C       172.16.2.0/24 is directly connected, Loopback1
C       172.16.3.0/24 is directly connected, Loopback2

R5#show ip bgp
BGP table version is 19, local router ID is 172.16.3.1
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
*> 4.4.4.4/32       55.55.55.2               0         32768 ?
*> 172.16.0.0/22    0.0.0.0                            32768 i
s> 172.16.2.0/24    0.0.0.0                  0         32768 i
s> 172.16.3.0/24    0.0.0.0                  0         32768 i

Router in AS 500 that is an eBGP with R5 in AS 10---->R4#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/193] via 10.1.1.1, 03:54:50, Serial2/0
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
55.0.0.0/30 is subnetted, 1 subnets
C 55.55.55.0 is directly connected, Serial2/3
5.0.0.0/32 is subnetted, 1 subnets
S 5.5.5.5 [1/0] via 55.55.55.1
172.16.0.0/22 is subnetted, 1 subnets
B 172.16.0.0 [20/0] via 5.5.5.5, 00:52:58
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
O 10.3.1.0/30 [110/192] via 10.1.1.1, 02:35:27, Serial2/0
O 10.2.1.0/30 [110/128] via 10.1.1.1, 03:54:50, Serial2/0
C 10.1.1.0/30 is directly connected, Serial2/0
C 10.50.1.1/32 is directly connected, Loopback5

[Julio E. Moisa]

Hi

Have you tried make ping with a source known from the other router? If the destination exists you could make ping, I see an aggregate address poiting to null0. Could you please share the configuration?.

Ping example:

ping 172.16.X.1 source 55.55.55.55  (assuming IP 55.55.55.55 is known at the other side) 

[BannerMOTD]

I created a null interface because for the aggregate route to be injected into the bgp routing table it needs to be associated with an interface? Correct me if i am wrong.

[Julio E. Moisa]

Hi, 

In order be able to advertise an aggregate address the prefixes must exist so you could use loopback or 1 loopback with a main network and many secondaries networks. And these prefixes must be advertised under the BGP AS.

:-)

[BannerMOTD]

R1#show ip bgp
BGP table version is 6, local router ID is 1.1.1.1
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
*> 1.1.1.1/32 0.0.0.0 0 32768 i
* i4.4.4.4/32 5.5.5.5 0 100 0 20 ?
*> 10.3.1.0/30 10.2.1.2 0 32768 ?
* i172.16.0.0/22 5.5.5.5 0 100 0 20 i
*> 10.1.1.2 0 32768 ?

This is from a iBGP router in AS 500.

[Julio E. Moisa]

Hi

I see the aggregate network into the BGP table. Are you able to ping from R1?

[BannerMOTD]

I was able to ping 172.16.2.1 source 1.1.1.1

[BannerMOTD]

I was able to ping 172.16.2.1 from 55.55.55.2. My main problem is that r1 does not know about the aggregate because I cannot get it advertised.

[BannerMOTD]

I think I need to put next-hop-self somewhere in there because the next hop to get to the aggregate route is the loopback of the router in AS10

[Jon Marshall]

When R4 advertises the summary address to R1 it will leave the next hop IP as 5.5.5.5 so on R4 you need to add under the BGP configuration -

"neighbor <R1 IP address> next-hop-self" 

Also as long as at least one of the subnets within the aggregate is in the BGP RIB the summary will be advertised ie. no need for a static route. 

Jon

[BannerMOTD]

Now is the ip address the router ID of R1 or is that a physical interface I am putting in because that is directly connected to R4?

[BannerMOTD]

After I do what you told me on R4 to do I attempt to ping the specific prefix under the aggregate and this happens.

10.1.1.2 is the physical interface ip address on R4 and 10.1.1.1 is the physical interface ip address on R1

R1#trac 172.16.2.1
R1#trac 172.16.2.1

Type escape sequence to abort.
Tracing the route to 172.16.2.1

1 10.1.1.2 24 msec 16 msec 20 msec
2 10.1.1.1 40 msec 40 msec 40 msec
3 * * *
4

R4#show ip bgp
BGP table version is 20, local router ID is 10.50.1.1
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
r>i1.1.1.1/32       10.1.1.1                 0    100      0 i
r i                 1.1.1.1                  0    100      0 i
r> 4.4.4.4/32       5.5.5.5                  0             0 20 ?
r>i10.3.1.0/30      10.1.1.1                 0    100      0 ?
r i                 1.1.1.1                  0    100      0 ?
* i10.50.1.1/32     77.77.77.2               0    100      0 ?
*>i172.16.0.0/22    10.1.1.1                 0    100      0 ?
* i                 1.1.1.1                  0    100      0 ?
*                   5.5.5.5                  0             0 20 i

R1#show ip bgp
BGP table version is 9, local router ID is 1.1.1.1
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
*> 1.1.1.1/32       0.0.0.0                  0         32768 i
r>i4.4.4.4/32       10.1.1.2                 0    100      0 20 ?
r i                 4.4.4.4                  0    100      0 20 ?
*> 10.3.1.0/30      10.2.1.2                 0         32768 ?
*> 172.16.0.0/22    10.1.1.2                 0         32768 ?

[Julio E. Moisa]

Hi

Is possible to have the configuration of both routers?

[BannerMOTD]

Building configuration...

Current configuration : 2741 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
ip tcp synwait-time 5
!
!
!
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface FastEthernet0/0
no ip address
shutdown
duplex half
!
interface FastEthernet1/0
no ip address
shutdown
duplex half
!
interface Serial2/0
ip address 10.1.1.1 255.255.255.252
serial restart-delay 0
!
interface Serial2/1
ip address 10.2.1.1 255.255.255.252
serial restart-delay 0
!
interface Serial2/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/3
no ip address
shutdown
serial restart-delay 0
!
interface Ethernet3/0
no ip address
shutdown
duplex half
!
interface Ethernet3/1
no ip address
shutdown
duplex half
!
interface Ethernet3/2
no ip address
shutdown
duplex half
!
interface Ethernet3/3
no ip address
shutdown
duplex half
!
interface Ethernet4/0
no ip address
shutdown
duplex half
!
interface Ethernet4/1
no ip address
shutdown
duplex half
!
interface Ethernet4/2
no ip address
shutdown
duplex half
!
interface Ethernet4/3
no ip address
shutdown
duplex half
!
interface Ethernet4/4
no ip address
shutdown
duplex half
!
interface Ethernet4/5
no ip address
shutdown
duplex half
!
interface Ethernet4/6
no ip address
shutdown
duplex half
!
interface Ethernet4/7
no ip address
shutdown
duplex half
!
interface FastEthernet5/0
no ip address
shutdown
duplex half
!
interface GigabitEthernet6/0
no ip address
shutdown
negotiation auto
!
router ospf 1
log-adjacency-changes
network 1.1.1.1 0.0.0.0 area 0
network 10.1.1.0 0.0.0.3 area 0
network 10.2.1.0 0.0.0.3 area 0
!
router bgp 500
no synchronization
bgp log-neighbor-changes
network 1.1.1.1 mask 255.255.255.255
redistribute static
neighbor 4.4.4.4 remote-as 500
neighbor 4.4.4.4 ebgp-multihop 255
neighbor 4.4.4.4 update-source Loopback0
neighbor 4.4.4.4 next-hop-self
neighbor 5.5.5.5 remote-as 20
neighbor 10.1.1.2 remote-as 500
neighbor 10.1.1.2 next-hop-self
neighbor 10.2.1.2 remote-as 500
no auto-summary
!
ip route 10.3.1.0 255.255.255.252 10.2.1.2
ip route 172.16.0.0 255.255.252.0 10.1.1.2
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
no cdp log mismatch duplex
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
gatekeeper
shutdown
!
!
line con 0
exec-timeout 0 0
privilege level 15
logging synchronous
stopbits 1
line aux 0
exec-timeout 0 0
privilege level 15
logging synchronous
stopbits 1
line vty 0 4
login
!
!
end

R4#show runn
Building configuration...

Current configuration : 2868 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
ip tcp synwait-time 5
!
!
!
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 4.4.4.4 255.255.255.255
!
interface Loopback5
ip address 10.50.1.1 255.255.255.255
!
interface FastEthernet0/0
no ip address
shutdown
duplex half
!
interface FastEthernet1/0
no ip address
shutdown
duplex half
!
interface Serial2/0
ip address 10.1.1.2 255.255.255.252
serial restart-delay 0
!
interface Serial2/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/3
ip address 55.55.55.2 255.255.255.252
serial restart-delay 0
!
interface Ethernet3/0
no ip address
shutdown
duplex half
!
interface Ethernet3/1
no ip address
shutdown
duplex half
!
interface Ethernet3/2
no ip address
shutdown
duplex half
!
interface Ethernet3/3
no ip address
shutdown
duplex half
!
interface Ethernet4/0
no ip address
shutdown
duplex half
!
interface Ethernet4/1
no ip address
shutdown
duplex half
!
interface Ethernet4/2
no ip address
shutdown
duplex half
!
interface Ethernet4/3
no ip address
shutdown
duplex half
!
interface Ethernet4/4
no ip address
shutdown
duplex half
!
interface Ethernet4/5
no ip address
shutdown
duplex half
!
interface Ethernet4/6
no ip address
shutdown
duplex half
!
interface Ethernet4/7
no ip address
shutdown
duplex half
!
interface FastEthernet5/0
no ip address
shutdown
duplex half
!
interface GigabitEthernet6/0
no ip address
shutdown
negotiation auto
!
router ospf 1
log-adjacency-changes
network 4.4.4.4 0.0.0.0 area 0
network 10.1.1.0 0.0.0.3 area 0
!
router bgp 500
no synchronization
bgp log-neighbor-changes
aggregate-address 172.16.0.0 255.255.252.0
neighbor 1.1.1.1 remote-as 500
neighbor 1.1.1.1 ebgp-multihop 255
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 next-hop-self
neighbor 3.3.3.3 remote-as 500
neighbor 3.3.3.3 ebgp-multihop 255
neighbor 3.3.3.3 update-source Loopback0
neighbor 5.5.5.5 remote-as 20
neighbor 5.5.5.5 ebgp-multihop 255
neighbor 5.5.5.5 update-source Loopback0
neighbor 10.1.1.1 remote-as 500
neighbor 10.1.1.1 next-hop-self
no auto-summary
!
ip route 5.5.5.5 255.255.255.255 55.55.55.1
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
no cdp log mismatch duplex
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
gatekeeper
shutdown
!
!
line con 0
exec-timeout 0 0
privilege level 15
logging synchronous
stopbits 1
line aux 0
exec-timeout 0 0
privilege level 15
logging synchronous
stopbits 1
line vty 0 4
login
!
!
end

Building configuration...

Current configuration : 2756 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R5
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
no ip icmp rate-limit unreachable
ip cef
ip tcp synwait-time 5
!
!
!
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
 ip address 5.5.5.5 255.255.255.255
!
interface Loopback1
 ip address 172.16.2.1 255.255.255.0
!
interface Loopback2
 ip address 172.16.3.1 255.255.255.0
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex half
!
interface FastEthernet1/0
 no ip address
 shutdown
 duplex half
!
interface Serial2/0
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/1
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/2
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/3
 ip address 55.55.55.1 255.255.255.252
 serial restart-delay 0
!
interface Ethernet3/0
 no ip address
 shutdown
 duplex half
!
interface Ethernet3/1
 no ip address
 shutdown
 duplex half
!
interface Ethernet3/2
 no ip address
 shutdown
 duplex half
!
interface Ethernet3/3
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/0
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/1
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/2
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/3
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/4
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/5
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/6
 no ip address
 shutdown
 duplex half
!
interface Ethernet4/7
 no ip address
 shutdown
 duplex half
!
interface FastEthernet5/0
 no ip address
 shutdown
 duplex half
!
interface GigabitEthernet6/0
 no ip address
 shutdown
 negotiation auto
!
router bgp 20
 no synchronization
 bgp log-neighbor-changes
 network 172.16.2.0 mask 255.255.255.0
 network 172.16.2.1 mask 255.255.255.255
 network 172.16.3.0 mask 255.255.255.0
 network 172.16.3.1 mask 255.255.255.255
 aggregate-address 172.16.0.0 255.255.252.0 summary-only
 redistribute static
 neighbor 4.4.4.4 remote-as 500
 neighbor 4.4.4.4 ebgp-multihop 255
 neighbor 4.4.4.4 update-source Loopback0
 neighbor 55.55.55.2 remote-as 500
 neighbor 55.55.55.2 next-hop-self
 no auto-summary
!
ip route 4.4.4.4 255.255.255.255 55.55.55.2
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
no cdp log mismatch duplex
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
gatekeeper
 shutdown
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
 stopbits 1
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
 stopbits 1
line vty 0 4
 login
!
!
end

[Jon Marshall]

Remove the following from R1 - 

neighbor 5.5.5.5 remote-as 20
neighbor 5.5.5.5 remote-as 20

ip route 172.16.0.0 255.255.252.0 10.1.1.2

then retest.

Jon