OSPF : Traffic flow behavior with varying OSPF cost

This post is to check the behavior of the network with varying OSPF cost on the link between OSPF neighbors.

Configurations requirements:

1. Used OSPF as the IGP protocol between the three locations
2. Looopback 0 will be used to established OSPF neighbors.
3. Run IBGP between the routers and neighbors should be formed via Loopback 2.
4. Change the OSPF cost on SYDNEY link towards MANILA to 1000 and check the traffic flow from MANILA towards SYDNEY router loopback 2. Questions to ask here, is the IBGP peering between SYDNEY and MANILA resetted? Is MANILA sending the advertisement via SYDNEY after SYDNEY link is costed out?
5. Finally, apply an OSPF cost of 1000 on the MANILA link and check the traffic flow towards SYDNEY router loopback 2.

Router Configurations:

a. IGP (OSPF configurations):

SYDNEY Router:

SYDNEY#show run | sec ospf
router ospf 1
router-id 1.1.1.1
network 1.1.1.1 0.0.0.0 area 0
network 11.11.11.11 0.0.0.0 area 0
network 192.168.12.0 0.0.0.255 area 0
network 192.168.13.0 0.0.0.255 area 0

TOKYO Router

TOKYO#show run | sec ospf

router ospf 1

router-id 2.2.2.2

network 2.2.2.2 0.0.0.0 area 0

network 22.22.22.22 0.0.0.0 area 0

network 192.168.12.0 0.0.0.255 area 0

network 192.168.23.0 0.0.0.255 area 0

MANILA Router:

MANILA#show run | sec ospf
router ospf 1
router-id 3.3.3.3
network 3.3.3.3 0.0.0.0 area 0
network 33.33.33.33 0.0.0.0 area 0
network 192.168.13.0 0.0.0.255 area 0
network 192.168.23.0 0.0.0.255 area 0

As verified the OSPF Neighbors were all formed:

SYDNEY#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/ – 00:00:39 192.168.13.3 Serial3/2
2.2.2.2 0 FULL/ – 00:00:34 192.168.12.2 Serial3/0

TOKYO#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/ – 00:00:37 192.168.23.3 Serial3/1
1.1.1.1 0 FULL/ – 00:00:39 192.168.12.1 Serial3/0
TOKYO#

MANILA#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 0 FULL/ – 00:00:37 192.168.23.2 Serial3/1
1.1.1.1 0 FULL/ – 00:00:34 192.168.13.1 Serial3/2
MANILA#

And as checked the loopback 2 interface were advertised via OSPF. This will be used for IBGP peerings.

TOKYO#show ip ospf route

OSPF Router with ID (2.2.2.2) (Process ID 1)

Base Topology (MTID 0)

Area BACKBONE(0)

Intra-area Route List
* 192.168.12.0/24, Intra, cost 64, area 0, Connected
via 192.168.12.2, Serial3/0
*> 192.168.13.0/24, Intra, cost 1064, area 0
via 192.168.12.1, Serial3/0
via 192.168.23.3, Serial3/1
* 192.168.23.0/24, Intra, cost 64, area 0, Connected
via 192.168.23.2, Serial3/1
*> 1.1.1.1/32, Intra, cost 65, area 0
via 192.168.12.1, Serial3/0
* 2.2.2.2/32, Intra, cost 1, area 0, Connected
via 2.2.2.2, Loopback0
*> 3.3.3.3/32, Intra, cost 65, area 0
via 192.168.23.3, Serial3/1
*> 11.11.11.11/32, Intra, cost 65, area 0
via 192.168.12.1, Serial3/0
* 22.22.22.22/32, Intra, cost 1, area 0, Connected
via 22.22.22.22, Loopback2
*> 33.33.33.33/32, Intra, cost 65, area 0
via 192.168.23.3, Serial3/1
TOKYO#

MANILA#show ip ospf route

OSPF Router with ID (3.3.3.3) (Process ID 1)

Base Topology (MTID 0)

Area BACKBONE(0)

Intra-area Route List
*> 192.168.12.0/24, Intra, cost 128, area 0
via 192.168.23.2, Serial3/1
* 192.168.13.0/24, Intra, cost 1000, area 0, Connected
via 192.168.13.3, Serial3/2
* 192.168.23.0/24, Intra, cost 64, area 0, Connected
via 192.168.23.3, Serial3/1
*> 1.1.1.1/32, Intra, cost 129, area 0
via 192.168.23.2, Serial3/1
*> 2.2.2.2/32, Intra, cost 65, area 0
via 192.168.23.2, Serial3/1
* 3.3.3.3/32, Intra, cost 1, area 0, Connected
via 3.3.3.3, Loopback0
*> 11.11.11.11/32, Intra, cost 129, area 0
via 192.168.23.2, Serial3/1
*> 22.22.22.22/32, Intra, cost 65, area 0
via 192.168.23.2, Serial3/1
* 33.33.33.33/32, Intra, cost 1, area 0, Connected
via 33.33.33.33, Loopback2
MANILA#

SYDNEY#show ip ospf route

OSPF Router with ID (1.1.1.1) (Process ID 1)

Base Topology (MTID 0)

Area BACKBONE(0)

Intra-area Route List

* 192.168.12.0/24, Intra, cost 64, area 0, Connected

via 192.168.12.1, Serial3/0

* 192.168.13.0/24, Intra, cost 1000, area 0, Connected

via 192.168.13.1, Serial3/2

*> 192.168.23.0/24, Intra, cost 128, area 0

via 192.168.12.2, Serial3/0

* 1.1.1.1/32, Intra, cost 1, area 0, Connected

via 1.1.1.1, Loopback0

*> 2.2.2.2/32, Intra, cost 65, area 0

via 192.168.12.2, Serial3/0

*> 3.3.3.3/32, Intra, cost 129, area 0

via 192.168.12.2, Serial3/0

* 11.11.11.11/32, Intra, cost 1, area 0, Connected

via 11.11.11.11, Loopback2

*> 22.22.22.22/32, Intra, cost 65, area 0

via 192.168.12.2, Serial3/0

*> 33.33.33.33/32, Intra, cost 129, area 0

via 192.168.12.2, Serial3/0

SYDNEY#

With the presence of the Loopback 2 addresses into the OSPF routing table , it ensures reachability of BGP TCP sessions required in order to formed BGP neighbors.

Now, I’m configuring the IBGP between routers:

SYDNEY#show run | sec bgp
ipv6 multicast rpf use-bgp
router bgp 1
bgp log-neighbor-changes
neighbor 22.22.22.22 remote-as 1
neighbor 22.22.22.22 update-source Loopback2
neighbor 33.33.33.33 remote-as 1
neighbor 33.33.33.33 update-source Loopback2

SYDNEY#

MANILA#show run | sec bgp
ipv6 multicast rpf use-bgp
router bgp 1
bgp log-neighbor-changes
neighbor 11.11.11.11 remote-as 1
neighbor 11.11.11.11 update-source Loopback2
neighbor 22.22.22.22 remote-as 1
neighbor 22.22.22.22 update-source Loopback2

MANILA#

TOKYO#show run | sec bgp
ipv6 multicast rpf use-bgp
router bgp 1
bgp log-neighbor-changes
neighbor 11.11.11.11 remote-as 1
neighbor 11.11.11.11 update-source Loopback2
neighbor 33.33.33.33 remote-as 1
neighbor 33.33.33.33 update-source Loopback2

TOKYO#

Let’s verify the BGP neighbors formed:

TOKYO#show ip bgp summary
BGP router identifier 22.22.22.22, local AS number 1
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
11.11.11.11 4 1 36 36 1 0 0 00:30:27 0
33.33.33.33 4 1 36 36 1 0 0 00:30:28 0
TOKYO#

MANILA#show ip bgp summary

BGP router identifier 33.33.33.33, local AS number 1

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

11.11.11.11 4 1 36 37 1 0 0 00:30:53 0

22.22.22.22 4 1 37 36 1 0 0 00:30:51 0

MANILA#

SYDNEY#show ip bgp summary

BGP router identifier 11.11.11.11, local AS number 1

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

22.22.22.22 4 1 37 37 1 0 0 00:31:13 0

33.33.33.33 4 1 37 37 1 0 0 00:31:15 0

SYDNEY#

The default OSPF cost is calculated as Cost = Reference Bandwidth/Interface Bandwidth . With my set up above, i notice that the default OSPF cost is 64 on all the 3 OSPF neighbors as I’m connecting them via a serial links with a bandwidth of 1.544 Mbps.

Example below from TOKYO router

TOKYO#show ip ospf interface s3/0
Serial3/0 is up, line protocol is up
Internet Address 192.168.12.2/24, Area 0, Attached via Network Statement
Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_POINT, Cost: 64
Topology-MTID Cost Disabled Shutdown Topology Name
0 64 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:03
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 3/3, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 1.1.1.1
Suppress hello for 0 neighbor(s)

TOKYO#show ip ospf interface s3/1
Serial3/1 is up, line protocol is up
Internet Address 192.168.23.2/24, Area 0, Attached via Network Statement
Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_POINT, Cost: 64
Topology-MTID Cost Disabled Shutdown Topology Name
0 64 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:02
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 4/4, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 3.3.3.3
Suppress hello for 0 neighbor(s)

Now, I want to check the traffic path from MANILA to SYDNEY’s Loopback 2 with an OSPF COST of 60 on both ends.

MANILA#traceroute 11.11.11.11
Type escape sequence to abort.
Tracing the route to 11.11.11.11
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.13.1 12 msec 16 msec 16 msec — Direct path
MANILA#

Similarly, I want to check the traffic path from SYDNEY to MANILA’s Loopback 2 with an OSPF COST of 60 on both ends.

SYDNEY#traceroute 33.33.33.33

Type escape sequence to abort.

Tracing the route to 33.33.33.33

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.13.3 32 msec 28 msec 8 msec — Direct path

MANILA#show ip ospf interface s3/2
Serial3/2 is up, line protocol is up
Internet Address 192.168.13.3/24, Area 0, Attached via Network Statement
Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_POINT, Cost: 64
Topology-MTID Cost Disabled Shutdown Topology Name
0 64 no no Base
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:06
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 3/3, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 1.1.1.1
Suppress hello for 0 neighbor(s)

SYDNEY#show ip ospf interface s3/2

Serial3/2 is up, line protocol is up

Internet Address 192.168.13.1/24, Area 0, Attached via Network Statement

Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 64

Topology-MTID Cost Disabled Shutdown Topology Name

0 64 no no Base

Transmit Delay is 1 sec, State POINT_TO_POINT

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

oob-resync timeout 40

Hello due in 00:00:04

Supports Link-local Signaling (LLS)

Cisco NSF helper support enabled

IETF NSF helper support enabled

Index 4/4, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 1, maximum is 1

Last flood scan time is 0 msec, maximum is 4 msec

Neighbor Count is 1, Adjacent neighbor count is 1

Adjacent with neighbor 3.3.3.3

Suppress hello for 0 neighbor(s)

SYDNEY#

Now, I want to change the behavior of SYDNEY traffic path towards MANILA’s loopback 2 by applying higher OSPF cost ( 1000) on the link towards MANILA.

SYDNEY(config-if)#ip ospf cost 1000

SYDNEY(config-if)#^Z

SYDNEY#

SYDNEY#config t

*Apr 30 23:51:19.655: %SYS-5-CONFIG_I: Configured from console by console

SYDNEY#show ip ospf interface s3/2

Serial3/2 is up, line protocol is up

Internet Address 192.168.13.1/24, Area 0, Attached via Network Statement

Process ID 1, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1000

Topology-MTID Cost Disabled Shutdown Topology Name

0 1000 no no Base

Transmit Delay is 1 sec, State POINT_TO_POINT

Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

oob-resync timeout 40

Hello due in 00:00:04

Supports Link-local Signaling (LLS)

Cisco NSF helper support enabled

IETF NSF helper support enabled

Index 4/4, flood queue length 0

Next 0x0(0)/0x0(0)

Last flood scan length is 1, maximum is 1

Last flood scan time is 0 msec, maximum is 4 msec

Neighbor Count is 1, Adjacent neighbor count is 1

Adjacent with neighbor 3.3.3.3

Suppress hello for 0 neighbor(s)

SYDNEY#

How was the traffic flow between SYDNEY towards MANILA? As seen above, path have been routed via TOKYO.

SYDNEY#traceroute 33.33.33.33

Type escape sequence to abort.

Tracing the route to 33.33.33.33

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.12.2 52 msec 20 msec 16 msec

2 192.168.23.3 52 msec 20 msec 44 msec

SYDNEY#

What about the traffic flow between MANILA to SYDNEY? As seen below, the path does not change and still using the direct path towards SYDNEY. This is due to the fact that MANILA OSPF process have seen that in order to get to 11.11.11.11 , it sees that the direct path have lesser OSPF cost than via TOKYO.

MANILA# traceroute 11.11.11.11

Type escape sequence to abort.

Tracing the route to 11.11.11.11

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.13.1 76 msec 52 msec 52 msec

MANILA#

I have enabled debug ip ospf lsa-generation and ip ospf flooding on SYDNEY router when I change the OSPF cost value to 1000 and notice 1 LSA were regenerated.

SYDNEY(config-if)#ip ospf cost 1000

SYDNEY(config-if)#

*May 1 00:25:53.675: OSPF-1 LSGEN: Scheduling rtr LSA for area 0

*May 1 00:25:54.179: OSPF-1 LSGEN: Build router LSA for area 0, router ID 1.1.1.1, seq 0x8000000E

*May 1 00:25:54.179: OSPF-1 FLOOD Se3/2: Add Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E to 3.3.3.3 retransmission list

*May 1 00:25:54.183: OSPF-1 FLOOD Se3/2: Add Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E to flood list

*May 1 00:25:54.183: OSPF-1 FLOOD Se3/2: Flooding update to 224.0.0.5 Area 0

*May 1 00:25:54.187: OSPF-1 FLOOD Se3/2: Send Type 1, LSID 1.1.1.1, Adv rtr 1.1.1.1, age 1, seq 0x8000000E (0)

*May 1 00:25:54.187: OSPF-1 FLOOD Se3/2: Remove Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E flood list

*May 1 00:25:54.191: OSPF-1 FLOOD Se3/2: Stop flood timer

*May 1 00:25:54.191: OSPF-1 FLOOD Se3/0: Add Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E to 2.2.2.2 retransmission list

*May 1 00:25:54.195: OSPF-1 FLOOD Se3/0: Add Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E

SYDNEY(config-if)# to flood list

*May 1 00:25:54.195: OSPF-1 FLOOD Se3/0: Flooding update to 224.0.0.5 Area 0

*May 1 00:25:54.199: OSPF-1 FLOOD Se3/0: Send Type 1, LSID 1.1.1.1, Adv rtr 1.1.1.1, age 1, seq 0x8000000E (0)

*May 1 00:25:54.199: OSPF-1 FLOOD Se3/0: Remove Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E flood list

*May 1 00:25:54.203: OSPF-1 FLOOD Se3/0: Stop flood timer

SYDNEY(config-if)#

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/0: Received ACK from 2.2.2.2

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/0: Rcv Ack Type 1, LSID 1.1.1.1, Adv rtr 1.1.1.1, age 1, seq 0x8000000E

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/0: Remove Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E from 2.2.2.2 retransmission list

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/2: Received ACK from 3.3.3.3

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/2: Rcv Ack Type 1, LSID 1.1.1.1, Adv rtr 1.1.1.1, age 1, seq 0x8000000E

*May 1 00:25:56.783: OSPF-1 FLOOD Se3/2: Remove Type 1 LSA ID 1.1.1.1 Adv rtr 1.1.1.1 Seq 8000000E from 3.3.3.3 retransmission list

SYDNEY(config-if)#

Results of debug ip ospf spf

SYDNEY(config-if)#ip ospf cost 1000

SYDNEY(config-if)#

*May 1 00:32:43.991: OSPF-1 MON : Schedule Full SPF in area 0, change in LSID 1.1.1.1, LSA type R

*May 1 00:32:43.991: OSPF-1 MON : reset throttling to 5000ms next wait-interval 10000ms

SYDNEY(config-if)#

*May 1 00:32:48.995: OSPF-1 INTRA: Running SPF for area 0, SPF-type Full

*May 1 00:32:48.995: OSPF-1 INTRA: Initializing to run spf

*May 1 00:32:48.999: OSPF-1 INTRA: spf_intra() – rebuilding the tree

*May 1 00:32:48.999: OSPF-1 INTRA: It is a router LSA 1.1.1.1. Link Count 6

*May 1 00:32:49.003: OSPF-1 INTRA: Processing link 0, id 1.1.1.1, link data 255.255.255.255, type 3

*May 1 00:32:49.003: OSPF-1 SPF : Add better path to LSA ID 1.1.1.1, gateway 1.1.1.1, dist 1

*May 1 00:32:49.007: OSPF-1 SPF : Add path: next-hop 1.1.1.1, interface Loopback0

*May 1 00:32:49.007: OSPF-1 INTRA: Processing link 1, id 11.11.11.11, link data 255.255.255.255, type 3

*May 1 00:32:49.007: OSPF-1 SPF : Add better path to LSA ID 11.11.11.11, gateway 11.11.11.11, dist 1

*May 1 00:32:49.011: OSPF-1 SPF : Add path: next-hop 11.11.11.11, interface Loopback2

*May 1 00:32:49.011: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.13.1, type 1

*Ma

SYDNEY(config-if)#y 1 00:32:49.015: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 192.168.13.3, dist 1000

*May 1 00:32:49.015: OSPF-1 INTRA: Putting LSA on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3

*May 1 00:32:49.019: OSPF-1 SPF : Add path: next-hop 192.168.13.3, interface Serial3/2

*May 1 00:32:49.019: OSPF-1 INTRA: Processing link 3, id 192.168.13.0, link data 255.255.255.0, type 3

*May 1 00:32:49.023: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 1000

*May 1 00:32:49.023: OSPF-1 SPF : Add path: next-hop 192.168.13.1, interface Serial3/2

*May 1 00:32:49.027: OSPF-1 INTRA: Processing link 4, id 2.2.2.2, link data 192.168.12.1, type 1

*May 1 00:32:49.027: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 192.168.12.2, dist 64

*May 1 00:32:49.027: OSPF-1 INTRA: Putting LSA on the clist LSID 2.2.2.2, Type 1, Adv Rtr. 2.2.2.2

*May 1 00:32:49.031: OSPF-1 INTRA: Upheap LSA ID 2.2.2.2, Type

SYDNEY(config-if)# 1, Adv 2.2.2.2 on clist from index 2 to 1

*May 1 00:32:49.031: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.031: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3

*May 1 00:32:49.031: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 64

*May 1 00:32:49.035: OSPF-1 SPF : Add path: next-hop 192.168.12.1, interface Serial3/0

*May 1 00:32:49.035: OSPF-1 INTRA: Downheap LSA ID 3.3.3.3, Type 1, Adv 3.3.3.3 on clist from index 1 to 1

*May 1 00:32:49.035: OSPF-1 INTRA: It is a router LSA 2.2.2.2. Link Count 6

*May 1 00:32:49.035: OSPF-1 INTRA: Processing link 0, id 2.2.2.2, link data 255.255.255.255, type 3

*May 1 00:32:49.035: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 2.2.2.2, dist 65

*May 1 00:32:49.035: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.035: OSPF-1 INTRA: Processing lin

SYDNEY(config-if)#k 1, id 22.22.22.22, link data 255.255.255.255, type 3

*May 1 00:32:49.035: OSPF-1 SPF : Add better path to LSA ID 22.22.22.22, gateway 22.22.22.22, dist 65

*May 1 00:32:49.035: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.035: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.23.2, type 1

*May 1 00:32:49.035: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 192.168.23.3, dist 128

*May 1 00:32:49.035: OSPF-1 INTRA: Improving LSA position on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3

*May 1 00:32:49.035: OSPF-1 INTRA: LSA already on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3

*May 1 00:32:49.035: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.035: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3

*May 1 00:32:49.035: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist

SYDNEY(config-if)# 128

*May 1 00:32:49.035: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.035: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.12.2, type 1

*May 1 00:32:49.035: OSPF-1 INTRA: Ignore newdist 128 olddist 0

*May 1 00:32:49.035: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3

*May 1 00:32:49.035: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 128

*May 1 00:32:49.039: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.039: OSPF-1 INTRA: Downheap LSA ID 3.3.3.3, Type 1, Adv 3.3.3.3 on clist from index 1 to 1

*May 1 00:32:49.039: OSPF-1 INTRA: It is a router LSA 3.3.3.3. Link Count 6

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 0, id 3.3.3.3, link data 255.255.255.255, type 3

*May 1 00:32:49.039: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 3.3.3.3, dist 129

*May 1 00:3

SYDNEY(config-if)#2:49.039: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 1, id 33.33.33.33, link data 255.255.255.255, type 3

*May 1 00:32:49.039: OSPF-1 SPF : Add better path to LSA ID 33.33.33.33, gateway 33.33.33.33, dist 129

*May 1 00:32:49.039: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 2, id 2.2.2.2, link data 192.168.23.3, type 1

*May 1 00:32:49.039: OSPF-1 INTRA: Ignore newdist 192 olddist 64

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3

*May 1 00:32:49.039: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist 192

*May 1 00:32:49.039: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.13.3, type 1

*May 1 00:32:49

SYDNEY(config-if)#.039: OSPF-1 INTRA: Ignore newdist 192 olddist 0

*May 1 00:32:49.039: OSPF-1 INTRA: Processing link 5, id 192.168.13.0, link data 255.255.255.0, type 3

*May 1 00:32:49.039: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 192

*May 1 00:32:49.039: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0

*May 1 00:32:49.039: OSPF-1 INTRA: Adding Stub nets

*May 1 00:32:49.039: OSPF-1 INTRA: Route update succeeded for 1.1.1.1/255.255.255.255, metric 1, Next Hop: Loopback0/1.1.1.1 area 0

*May 1 00:32:49.043: OSPF-1 INTRA: Route update succeeded for 2.2.2.2/255.255.255.255, metric 65, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.043: OSPF-1 INTRA: Route update succeeded for 3.3.3.3/255.255.255.255, metric 129, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.043: OSPF-1 INTRA: Route update succeeded for 11.11.11.11/255.255.255.255, metric 1, Next Hop: Loopback2/11.11.11.11 area 0

*May 1 00:32:4

SYDNEY(config-if)#9.043: OSPF-1 INTRA: Route update succeeded for 22.22.22.22/255.255.255.255, metric 65, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.043: OSPF-1 INTRA: Route update succeeded for 33.33.33.33/255.255.255.255, metric 129, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.047: OSPF-1 INTRA: Route update succeeded for 192.168.12.0/255.255.255.0, metric 64, Next Hop: Serial3/0/192.168.12.1 area 0

*May 1 00:32:49.047: OSPF-1 INTRA: Route update succeeded for 192.168.13.0/255.255.255.0, metric 192, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.047: OSPF-1 INTRA: Route update succeeded for 192.168.23.0/255.255.255.0, metric 128, Next Hop: Serial3/0/192.168.12.2 area 0

*May 1 00:32:49.047: OSPF-1 INTRA: Entered intra-area route sync for area 0

*May 1 00:32:49.051: OSPF-1 INTRA: Entered intra-area route sync for area 0

*May 1 00:32:49.051: OSPF-1 INTER: Check and generate summary LSA into all areas

*May 1 00:32:49.055: OSPF-1 INTER: Running spf for summaries area 0

*May 1 00:32:49.055: OSPF-1 INTER: Entered inter-area route sync for area 0

*May 1 00:32:49.059: OSPF-1 INTER: Entered inter-area route sync for area 0

*May 1 00:32:49.059: OSPF-1 EXTER: Started Building Type 5 External Routes

*May 1 00:32:49.059: OSPF-1 EXTER: Started Building Type 7 External Routes

*May 1 00:32:49.063: OSPF-1 EXTER: Entered External route sync for area dummy area

*May 1 00:32:49.063: OSPF-1 EXTER: Entered NSSA route sync for area 0

*May 1 00:32:49.067: OSPF-1 EXTER: Entered NSSA route sync for area 0

*May 1 00:32:49.067: OSPF-1 MON : Setting next wait-interval to 10000ms

SYDNEY(config-if)#

Now, I will also costed out MANILA link to SYDNEY.

MANILA(config-if)#ip ospf cost 1000
MANILA(config-if)#
*May 1 00:38:10.939: OSPF-1 LSGEN: Scheduling rtr LSA for area 0
*May 1 00:38:11.443: OSPF-1 LSGEN: Build router LSA for area 0, router ID 3.3.3.3, seq 0x80000009
*May 1 00:38:11.447: OSPF-1 MON : Schedule Full SPF in area 0, change in LSID 3.3.3.3, LSA type R
*May 1 00:38:11.451: OSPF-1 MON : reset throttling to 5000ms next wait-interval 10000ms
MANILA(config-if)#
*May 1 00:38:16.451: OSPF-1 INTRA: Running SPF for area 0, SPF-type Full
*May 1 00:38:16.451: OSPF-1 INTRA: Initializing to run spf
*May 1 00:38:16.455: OSPF-1 INTRA: spf_intra() – rebuilding the tree
*May 1 00:38:16.455: OSPF-1 INTRA: It is a router LSA 3.3.3.3. Link Count 6
*May 1 00:38:16.459: OSPF-1 INTRA: Processing link 0, id 3.3.3.3, link data 255.255.255.255, type 3
*May 1 00:38:16.459: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 3.3.3.3, dist 1
*May 1 00:38:16.463: OSPF-1 SPF : Add path: next-hop 3.3.3.3, interface Loopback0
*May 1 00:38:16.463: OSPF-1 INTRA: Processing link 1, id 33.33.33.33, link data 255.255.255.255, type 3
*May 1 00:38:16.467: OSPF-1 SPF : Add better path to LSA ID 33.33.33.33, gateway 33.33.33.33, dist 1
*May 1 00:38:16.467: OSPF-1 SPF : Add path: next-hop 33.33.33.33, interface Loopback2
*May 1 00:38:16.467: OSPF-1 INTRA: Processing link 2, id 2.2.2.2, link data 192.168.23.3, type 1
*Ma
MANILA(config-if)#y 1 00:38:16.471: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 192.168.23.2, dist 64
*May 1 00:38:16.471: OSPF-1 INTRA: Putting LSA on the clist LSID 2.2.2.2, Type 1, Adv Rtr. 2.2.2.2
*May 1 00:38:16.475: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.475: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3
*May 1 00:38:16.479: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist 64
*May 1 00:38:16.479: OSPF-1 SPF : Add path: next-hop 192.168.23.3, interface Serial3/1
*May 1 00:38:16.483: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.13.3, type 1
*May 1 00:38:16.483: OSPF-1 SPF : Add better path to LSA ID 1.1.1.1, gateway 192.168.13.1, dist 1000
*May 1 00:38:16.487: OSPF-1 INTRA: Putting LSA on the clist LSID 1.1.1.1, Type 1, Adv Rtr. 1.1.1.1
*May 1 00:38:16.487: OSPF-1 INTRA: Upheap LSA ID 1.1.1.1, Type 1
MANILA(config-if)#, Adv 1.1.1.1 on clist from index 2 to 2
*May 1 00:38:16.487: OSPF-1 SPF : Add path: next-hop 192.168.13.1, interface Serial3/2
*May 1 00:38:16.491: OSPF-1 INTRA: Processing link 5, id 192.168.13.0, link data 255.255.255.0, type 3
*May 1 00:38:16.491: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 1000
*May 1 00:38:16.495: OSPF-1 SPF : Add path: next-hop 192.168.13.3, interface Serial3/2
*May 1 00:38:16.495: OSPF-1 INTRA: Downheap LSA ID 1.1.1.1, Type 1, Adv 1.1.1.1 on clist from index 1 to 1
*May 1 00:38:16.499: OSPF-1 INTRA: It is a router LSA 2.2.2.2. Link Count 6
*May 1 00:38:16.499: OSPF-1 INTRA: Processing link 0, id 2.2.2.2, link data 255.255.255.255, type 3
*May 1 00:38:16.499: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 2.2.2.2, dist 65
*May 1 00:38:16.499: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.499: OSPF-1 INTRA: Processing lin
MANILA(config-if)#k 1, id 22.22.22.22, link data 255.255.255.255, type 3
*May 1 00:38:16.503: OSPF-1 SPF : Add better path to LSA ID 22.22.22.22, gateway 22.22.22.22, dist 65
*May 1 00:38:16.503: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.503: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.23.2, type 1
*May 1 00:38:16.503: OSPF-1 INTRA: Ignore newdist 128 olddist 0
*May 1 00:38:16.503: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3
*May 1 00:38:16.503: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist 128
*May 1 00:38:16.503: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.503: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.12.2, type 1
*May 1 00:38:16.503: OSPF-1 SPF : Add better path to LSA ID 1.1.1.1, gateway 192.168.12.1, dist 128
*May 1 00:38:16.503: OSPF-1 INTRA: Impro
MANILA(config-if)#ving LSA position on the clist LSID 1.1.1.1, Type 1, Adv Rtr. 1.1.1.1
*May 1 00:38:16.503: OSPF-1 INTRA: LSA already on the clist LSID 1.1.1.1, Type 1, Adv Rtr. 1.1.1.1
*May 1 00:38:16.503: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.503: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3
*May 1 00:38:16.503: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 128
*May 1 00:38:16.503: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.503: OSPF-1 INTRA: Downheap LSA ID 1.1.1.1, Type 1, Adv 1.1.1.1 on clist from index 1 to 1
*May 1 00:38:16.503: OSPF-1 INTRA: It is a router LSA 1.1.1.1. Link Count 6
*May 1 00:38:16.503: OSPF-1 INTRA: Processing link 0, id 1.1.1.1, link data 255.255.255.255, type 3
*May 1 00:38:16.503: OSPF-1 SPF : Add better path to LSA ID 1.1.1.1, gateway 1.1.1.1, dist 129
*May 1 00:3
MANILA(config-if)#8:16.503: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.507: OSPF-1 INTRA: Processing link 1, id 11.11.11.11, link data 255.255.255.255, type 3
*May 1 00:38:16.507: OSPF-1 SPF : Add better path to LSA ID 11.11.11.11, gateway 11.11.11.11, dist 129
*May 1 00:38:16.507: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.507: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.13.1, type 1
*May 1 00:38:16.507: OSPF-1 INTRA: Ignore newdist 1128 olddist 0
*May 1 00:38:16.507: OSPF-1 INTRA: Processing link 3, id 192.168.13.0, link data 255.255.255.0, type 3
*May 1 00:38:16.507: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 1128
*May 1 00:38:16.507: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.507: OSPF-1 INTRA: Processing link 4, id 2.2.2.2, link data 192.168.12.1, type 1
*May 1 00:38:1
MANILA(config-if)#6.507: OSPF-1 INTRA: Ignore newdist 192 olddist 64
*May 1 00:38:16.507: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3
*May 1 00:38:16.507: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 192
*May 1 00:38:16.507: OSPF-1 SPF : Add path: next-hop 192.168.23.2, interface Serial3/1
*May 1 00:38:16.507: OSPF-1 INTRA: Adding Stub nets
*May 1 00:38:16.507: OSPF-1 INTRA: Route update succeeded for 1.1.1.1/255.255.255.255, metric 129, Next Hop: Serial3/1/192.168.23.2 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 2.2.2.2/255.255.255.255, metric 65, Next Hop: Serial3/1/192.168.23.2 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 3.3.3.3/255.255.255.255, metric 1, Next Hop: Loopback0/3.3.3.3 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 11.11.11.11/255.255.255.255, metric 129, Next Hop: Serial3/1/192.168.23.2 area 0
*May 1 00
MANILA(config-if)#:38:16.511: OSPF-1 INTRA: Route update succeeded for 22.22.22.22/255.255.255.255, metric 65, Next Hop: Serial3/1/192.168.23.2 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 33.33.33.33/255.255.255.255, metric 1, Next Hop: Loopback2/33.33.33.33 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 192.168.12.0/255.255.255.0, metric 128, Next Hop: Serial3/1/192.168.23.2 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 192.168.13.0/255.255.255.0, metric 1000, Next Hop: Serial3/2/192.168.13.3 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Route update succeeded for 192.168.23.0/255.255.255.0, metric 64, Next Hop: Serial3/1/192.168.23.3 area 0
*May 1 00:38:16.511: OSPF-1 INTRA: Entered intra-area route sync for area 0
*May 1 00:38:16.519: OSPF-1 INTRA: Entered intra-area route sync for area 0
*May 1 00:38:16.519: OSPF-1 INTER: Check and generate summary LSA into all areas
*May 1 00:38:16.523: OSPF-1 INTER: Running
MANILA(config-if)#spf for summaries area 0
*May 1 00:38:16.523: OSPF-1 INTER: Entered inter-area route sync for area 0
*May 1 00:38:16.523: OSPF-1 INTER: Entered inter-area route sync for area 0
*May 1 00:38:16.527: OSPF-1 EXTER: Started Building Type 5 External Routes
*May 1 00:38:16.527: OSPF-1 EXTER: Started Building Type 7 External Routes
*May 1 00:38:16.527: OSPF-1 EXTER: Entered External route sync for area dummy area
*May 1 00:38:16.531: OSPF-1 EXTER: Entered External route sync for area dummy area
*May 1 00:38:16.531: OSPF-1 EXTER: Entered NSSA route sync for area 0
*May 1 00:38:16.535: OSPF-1 EXTER: Entered NSSA route sync for area 0
*May 1 00:38:16.535: OSPF-1 MON : Setting next wait-interval to 10000ms
MANILA(config-if)#

Logs captured on SYDNEY router when the OSPF cost is applied on the MANILA link,

SYDNEY#
*May 1 00:38:11.575: OSPF-1 SPF : Detect change in LSA type 1, LSID 3.3.3.3 from 3.3.3.3 area 0
*May 1 00:38:11.579: OSPF-1 MON : Schedule Full SPF in area 0, change in LSID 3.3.3.3, LSA type R
*May 1 00:38:11.579: OSPF-1 MON : reset throttling to 5000ms next wait-interval 10000ms
SYDNEY#
*May 1 00:38:16.579: OSPF-1 INTRA: Running SPF for area 0, SPF-type Full
*May 1 00:38:16.579: OSPF-1 INTRA: Initializing to run spf
*May 1 00:38:16.583: OSPF-1 INTRA: spf_intra() – rebuilding the tree
*May 1 00:38:16.583: OSPF-1 INTRA: It is a router LSA 1.1.1.1. Link Count 6
*May 1 00:38:16.587: OSPF-1 INTRA: Processing link 0, id 1.1.1.1, link data 255.255.255.255, type 3
*May 1 00:38:16.587: OSPF-1 SPF : Add better path to LSA ID 1.1.1.1, gateway 1.1.1.1, dist 1
*May 1 00:38:16.591: OSPF-1 SPF : Add path: next-hop 1.1.1.1, interface Loopback0
*May 1 00:38:16.591: OSPF-1 INTRA: Processing link 1, id 11.11.11.11, link data 255.255.255.255, type 3
*May 1 00:38:16.595: OSPF-1 SPF : Add better path to LSA ID 11.11.11.11, gateway 11.11.11.11, dist 1
*May 1 00:38:16.595: OSPF-1 SPF : Add path: next-hop 11.11.11.11, interface Loopback2
*May 1 00:38:16.595: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.13.1, type 1
*Ma
SYDNEY#y 1 00:38:16.599: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 192.168.13.3, dist 1000
*May 1 00:38:16.599: OSPF-1 INTRA: Putting LSA on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3
*May 1 00:38:16.603: OSPF-1 SPF : Add path: next-hop 192.168.13.3, interface Serial3/2
*May 1 00:38:16.603: OSPF-1 INTRA: Processing link 3, id 192.168.13.0, link data 255.255.255.0, type 3
*May 1 00:38:16.607: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 1000
*May 1 00:38:16.607: OSPF-1 SPF : Add path: next-hop 192.168.13.1, interface Serial3/2
*May 1 00:38:16.611: OSPF-1 INTRA: Processing link 4, id 2.2.2.2, link data 192.168.12.1, type 1
*May 1 00:38:16.611: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 192.168.12.2, dist 64
*May 1 00:38:16.611: OSPF-1 INTRA: Putting LSA on the clist LSID 2.2.2.2, Type 1, Adv Rtr. 2.2.2.2
*May 1 00:38:16.615: OSPF-1 INTRA: Upheap LSA ID 2.2.2.2, Type
SYDNEY# 1, Adv 2.2.2.2 on clist from index 2 to 1
*May 1 00:38:16.615: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.619: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3
*May 1 00:38:16.619: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 64
*May 1 00:38:16.619: OSPF-1 SPF : Add path: next-hop 192.168.12.1, interface Serial3/0
*May 1 00:38:16.619: OSPF-1 INTRA: Downheap LSA ID 3.3.3.3, Type 1, Adv 3.3.3.3 on clist from index 1 to 1
*May 1 00:38:16.619: OSPF-1 INTRA: It is a router LSA 2.2.2.2. Link Count 6
*May 1 00:38:16.619: OSPF-1 INTRA: Processing link 0, id 2.2.2.2, link data 255.255.255.255, type 3
*May 1 00:38:16.619: OSPF-1 SPF : Add better path to LSA ID 2.2.2.2, gateway 2.2.2.2, dist 65
*May 1 00:38:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing lin
SYDNEY#k 1, id 22.22.22.22, link data 255.255.255.255, type 3
*May 1 00:38:16.623: OSPF-1 SPF : Add better path to LSA ID 22.22.22.22, gateway 22.22.22.22, dist 65
*May 1 00:38:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 2, id 3.3.3.3, link data 192.168.23.2, type 1
*May 1 00:38:16.623: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 192.168.23.3, dist 128
*May 1 00:38:16.623: OSPF-1 INTRA: Improving LSA position on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3
*May 1 00:38:16.623: OSPF-1 INTRA: LSA already on the clist LSID 3.3.3.3, Type 1, Adv Rtr. 3.3.3.3
*May 1 00:38:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3
*May 1 00:38:16.623: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist
SYDNEY# 128
*May 1 00:38:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.12.2, type 1
*May 1 00:38:16.623: OSPF-1 INTRA: Ignore newdist 128 olddist 0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 5, id 192.168.12.0, link data 255.255.255.0, type 3
*May 1 00:38:16.623: OSPF-1 SPF : Add better path to LSA ID 192.168.12.255, gateway 192.168.12.0, dist 128
*May 1 00:38:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Downheap LSA ID 3.3.3.3, Type 1, Adv 3.3.3.3 on clist from index 1 to 1
*May 1 00:38:16.623: OSPF-1 INTRA: It is a router LSA 3.3.3.3. Link Count 6
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 0, id 3.3.3.3, link data 255.255.255.255, type 3
*May 1 00:38:16.623: OSPF-1 SPF : Add better path to LSA ID 3.3.3.3, gateway 3.3.3.3, dist 129
*May 1 00:3
SYDNEY#8:16.623: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.623: OSPF-1 INTRA: Processing link 1, id 33.33.33.33, link data 255.255.255.255, type 3
*May 1 00:38:16.627: OSPF-1 SPF : Add better path to LSA ID 33.33.33.33, gateway 33.33.33.33, dist 129
*May 1 00:38:16.627: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.627: OSPF-1 INTRA: Processing link 2, id 2.2.2.2, link data 192.168.23.3, type 1
*May 1 00:38:16.627: OSPF-1 INTRA: Ignore newdist 192 olddist 64
*May 1 00:38:16.627: OSPF-1 INTRA: Processing link 3, id 192.168.23.0, link data 255.255.255.0, type 3
*May 1 00:38:16.627: OSPF-1 SPF : Add better path to LSA ID 192.168.23.255, gateway 192.168.23.0, dist 192
*May 1 00:38:16.627: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.627: OSPF-1 INTRA: Processing link 4, id 1.1.1.1, link data 192.168.13.3, type 1
*May 1 00:38:16
SYDNEY#.627: OSPF-1 INTRA: Ignore newdist 1128 olddist 0
*May 1 00:38:16.627: OSPF-1 INTRA: Processing link 5, id 192.168.13.0, link data 255.255.255.0, type 3
*May 1 00:38:16.627: OSPF-1 SPF : Add better path to LSA ID 192.168.13.255, gateway 192.168.13.0, dist 1128
*May 1 00:38:16.627: OSPF-1 SPF : Add path: next-hop 192.168.12.2, interface Serial3/0
*May 1 00:38:16.627: OSPF-1 INTRA: Adding Stub nets
*May 1 00:38:16.627: OSPF-1 INTRA: Route update succeeded for 1.1.1.1/255.255.255.255, metric 1, Next Hop: Loopback0/1.1.1.1 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 2.2.2.2/255.255.255.255, metric 65, Next Hop: Serial3/0/192.168.12.2 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 3.3.3.3/255.255.255.255, metric 129, Next Hop: Serial3/0/192.168.12.2 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 11.11.11.11/255.255.255.255, metric 1, Next Hop: Loopback2/11.11.11.11 area 0
*May 1 00:38
SYDNEY#:16.631: OSPF-1 INTRA: Route update succeeded for 22.22.22.22/255.255.255.255, metric 65, Next Hop: Serial3/0/192.168.12.2 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 33.33.33.33/255.255.255.255, metric 129, Next Hop: Serial3/0/192.168.12.2 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 192.168.12.0/255.255.255.0, metric 64, Next Hop: Serial3/0/192.168.12.1 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 192.168.13.0/255.255.255.0, metric 1000, Next Hop: Serial3/2/192.168.13.1 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Route update succeeded for 192.168.23.0/255.255.255.0, metric 128, Next Hop: Serial3/0/192.168.12.2 area 0
*May 1 00:38:16.631: OSPF-1 INTRA: Entered intra-area route sync for area 0
*May 1 00:38:16.635: OSPF-1 INTRA: Entered intra-area route sync for area 0
*May 1 00:38:16.635: OSPF-1 INTER: Check and generate summary LSA into all areas
*May 1 00:38:16.635: OSPF-1 INTER: Running
SYDNEY#spf for summaries area 0
*May 1 00:38:16.635: OSPF-1 INTER: Entered inter-area route sync for area 0
*May 1 00:38:16.635: OSPF-1 INTER: Entered inter-area route sync for area 0
*May 1 00:38:16.635: OSPF-1 EXTER: Started Building Type 5 External Routes
*May 1 00:38:16.635: OSPF-1 EXTER: Started Building Type 7 External Routes
*May 1 00:38:16.635: OSPF-1 EXTER: Entered External route sync for area dummy area
*May 1 00:38:16.635: OSPF-1 EXTER: Entered External route sync for area dummy area
*May 1 00:38:16.635: OSPF-1 EXTER: Entered NSSA route sync for area 0
*May 1 00:38:16.635: OSPF-1 EXTER: Entered NSSA route sync for area 0
*May 1 00:38:16.635: OSPF-1 MON : Setting next wait-interval to 10000ms
SYDNEY#

Traffic flow from SYDNEY TO MANILA :

SYDNEY#traceroute 33.33.33.33

Type escape sequence to abort.

Tracing the route to 33.33.33.33

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.12.2 52 msec 16 msec 16 msec

2 192.168.23.3 52 msec 16 msec 24 msec

SYDNEY#

Traffic Flow from MANILA to SYDNEY is now via TOKYO.

MANILA#traceroute 11.11.11.11

Type escape sequence to abort.

Tracing the route to 11.11.11.11

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.23.2 52 msec 20 msec 12 msec

2 192.168.12.1 12 msec 48 msec 16 msec

MANILA#

As also notice, BGP were NOT resetted.

SYDNEY#show ip bgp summary

BGP router identifier 11.11.11.11, local AS number 1

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

22.22.22.22 4 1 111 111 1 0 0 01:38:41 0

33.33.33.33 4 1 111 111 1 0 0 01:38:43 0

SYDNEY#

MANILA#show ip bgp summary

BGP router identifier 33.33.33.33, local AS number 1

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

11.11.11.11 4 1 112 112 1 0 0 01:39:13 0

22.22.22.22 4 1 112 112 1 0 0 01:39:11 0

MANILA#

In Summary:

1. OSPF cost applied on interface is uni-directional. This means that when a OSPF links were applied with higher OSPF cost manually, the router will NOT used this link to send out OSPF Hello packets but the neighboring OSPF router will still continue to send packet via the direct link as it sees a lower OSPF cost.

As seen the 33.33.33.33 were learned via OSPF via TOKYO.

SYDNEY#show ip route ospf
Codes: L – local, 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, H – NHRP, l – LISP
+ – replicated route, % – next hop override

Gateway of last resort is not set

2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/65] via 192.168.12.2, 01:49:34, Serial3/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/129] via 192.168.12.2, 00:04:24, Serial3/0
22.0.0.0/32 is subnetted, 1 subnets
O 22.22.22.22 [110/65] via 192.168.12.2, 01:49:34, Serial3/0
33.0.0.0/32 is subnetted, 1 subnets
O 33.33.33.33 [110/129] via 192.168.12.2, 00:04:24, Serial3/0
O 192.168.23.0/24 [110/128] via 192.168.12.2, 01:49:34, Serial3/0
SYDNEY#

2. This is causing an assymetric routing between MANILA and SYDNEY as seen from the traceroutes below:

SYDNEY#traceroute 33.33.33.33
Type escape sequence to abort.
Tracing the route to 33.33.33.33
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.12.2 52 msec 16 msec 16 msec
2 192.168.23.3 52 msec 16 msec 24 msec
SYDNEY#

MANILA#traceroute 11.11.11.11

Type escape sequence to abort.

Tracing the route to 11.11.11.11

VRF info: (vrf in name/id, vrf out name/id)

1 192.168.13.1 68 msec 80 msec 32 msec

MANILA is learning the loopback 2 address of SYDNEY via the direct link.

MANILA#show ip route ospf

Codes: L – local, 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, H – NHRP, l – LISP

+ – replicated route, % – next hop override

Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets

O 1.1.1.1 [110/65] via 192.168.13.1, 00:01:17, Serial3/2

2.0.0.0/32 is subnetted, 1 subnets

O 2.2.2.2 [110/65] via 192.168.23.2, 00:01:17, Serial3/1

11.0.0.0/32 is subnetted, 1 subnets

O 11.11.11.11 [110/65] via 192.168.13.1, 00:01:17, Serial3/2

22.0.0.0/32 is subnetted, 1 subnets

O 22.22.22.22 [110/65] via 192.168.23.2, 00:01:17, Serial3/1

O 192.168.12.0/24 [110/128] via 192.168.23.2, 00:01:17, Serial3/1

[110/128] via 192.168.13.1, 00:01:17, Serial3/2

NETWORK LESSON