OcNOS-RON-6.3.1 : Layer 3 Guide : Layer 3 Unicast Configuration Guide : OSPFv2 : OSPF Stub Router Advertisement
OSPF Stub Router Advertisement
The OSPF Stub router feature lets you to prevent a new router in any network from being used as a transit router.
This feature enables the new router to originate link-state advertisement(LSAs) with a maximum metric, thereby causing other routers in the network to prefer alternate-paths instead of using the new router as a transit path to forward traffic. Thereby this feature allows switching and routing functions to be up and running and routing tables to converge before transit traffic is routed again through this new router
Also a startup timer can be configured on this new router enabling it to advertise a maximum metric when the router is started or reloaded
The configuration given below enables the router R3 to advertise router-LSAs/summary-LSAs with maximum metric two routers in Area 0 connecting to network 10.10.10.0/24.
Note: Configure one interface so that it belongs to only one area. It is possible, however, to configure different interfaces on a router to belong to different areas.
Topology
Figure 4-24: OSPF Stub Router Advertisement Topology
 
 
Configuration
R1
 
#configure terminal
Enter configure mode
(config)#router ospf 1
Configure the routing process, and specify the Process ID (1). The Process ID should be a unique positive integer identifying the routing process.
(config)#ospf router-id 1.1.1.1
Configure the OSPF router-id
(config-router)#network 10.1.2.0/24 area 0
Define the interface (10.1.2.0/24) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area).
(config-router)#network 10.1.3.0/24 area 0
Define the interface (10.1.3.0/24) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area).
(config-router)#exit
Exit router mode
(config)#interface eth1
Enter the interface configuration mode for interface eth1
(config-if)#ip ospf cost 10
Configure the OSPF cost for the interface
(config-if)#exit
Exit the interface configuration mode
(config)#commit
Commit the candidate configuration to the running configuration.
R2
 
#configure terminal
Enter configure mode
(config)#router ospf 1
Configure the routing process, and specify the Process ID (1). The Process ID should be a unique positive integer identifying the routing process.
(config)#ospf router-id 1.1.1.2
Configure the OSPF router-id
(config-router)#network 10.1.2.0/24 area 0
Define the interface (10.1.2.0/24) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area).
(config-router)#network 10.2.4.0/24 area 1
Define the interface (10.2.4.0/24) on which OSPF runs, and associate the area ID (1) with the interface
(config-router)#exit
Exit router mode
(config)#commit
Commit the candidate configuration to the running configuration.
R3
 
#configure terminal
Enter configure mode
(config)#router ospf 1
Configure the routing process, and specify the Process ID (1). The Process ID should be a unique positive integer identifying the routing process.
(config)#ospf router-id 1.1.1.3
Configure the OSPF router-id
(config-router)#network 1.1.1.3/32 area 0
Define the interface (1.1.1.3/32) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area).
(config-router)#network 10.1.3.0/24 area 0
Define the interface (10.1.3.0/24) on which OSPF runs, and associate the area ID (0) with the interface (area ID 0 specifies the backbone area).
(config-router)#network 10.3.4.0/24 area 1
Define the interface (10.3.4.0/24) on which OSPF runs, and associate the area ID (1) with the interface
(config-router)#max-metric router-lsa include-stub summary-lsa 100
Configure the router to advertise max-metric for router-LSAs, for stub-networks of router-LSAs and to advertise a metric value of 100 for summary-LSAs
(config-router)# max-metric router-lsa on-startup 300 include-stub summary-lsa 222
Configure the router to advertise max-metric for router-LSAs, for stub-networks of router-LSAs and to advertise a metric value of 222 for summary-LSAs on-startup
(config-router)#exit
Exit router mode
(config)#commit
Commit the candidate configuration to the running configuration.
R4
 
#configure terminal
Enter configure mode
(config)#router ospf 1
Configure the routing process, and specify the Process ID (1). The Process ID should be a unique positive integer identifying the routing process.
(config)#ospf router-id 1.1.1.4
Configure the OSPF router-id
(config-router)#network 10.2.4.0/24 area 1
Define the interface (10.2.4.0/24) on which OSPF runs, and associate the area ID (1) with the interface
(config-router)#network 10.3.4.0/24 area 1
Define the interface (10.3.4.0/24) on which OSPF runs, and associate the area ID (1) with the interface
(config-router)#network 200.1.1.0/24 area 1
Define the interface (200.1.1.0/24) on which OSPF runs, and associate the area ID (1) with the interface
(config-router)#exit
Exit router mode
(config)#commit
Commit the candidate configuration to the running configuration.
Validation
R3
R3#show running-config ospf
!
router ospf 1
ospf router-id 1.1.1.3
max-metric router-lsa include-stub summary-lsa 100
max-metric router-lsa on-startup 300 include-stub summary-lsa 222
network 1.1.1.3/32 area 0.0.0.0
network 10.1.3.0/24 area 0.0.0.0
network 10.3.4.0/24 area 0.0.0.1
!
R3#
 
 
R3#show ip ospf
Routing Process "ospf 1" with ID 1.1.1.3
Process uptime is 1 hour 20 minutes
Process bound to VRF default
Conforms to RFC2328, and RFC1583 Compatibility flag is disabled
Supports only single TOS(TOS0) routes
Supports opaque LSA
Originating router-LSAs with maximum metric
Condition: always State: active
Advertise stub links with maximum metric in router-LSAs
Advertise summary-LSAs with metric 100
Condition: on start-up for 300 seconds State: Inactive
Advertise stub links with maximum metric in router-LSAs
Advertise summary-LSAs with metric 222
Supports Graceful Restart
This router is an ABR, ABR Type is Alternative Cisco (RFC3509)
SPF schedule delay initial 0 secs 500 msecs
SPF schedule delay min 0 secs 500 msecs
SPF schedule delay max 50 secs 0 msecs
Refresh timer 10 secs
Number of incoming current DD exchange neighbors 0/64
Number of outgoing current DD exchange neighbors 0/64
Initial LSA throttle delay 0 secs 0 msecs
Minimum hold time for LSA throttle 5 secs 0 msecs
Maximum wait time for LSA throttle 5 secs 0 msecs
Minimum LSA arrival 1 secs 0 msecs
Number of external LSA 0. Checksum 0x000000
Number of opaque AS LSA 0. Checksum 0x000000
Number of non-default external LSA 0
External LSA database is unlimited.
Number of LSA originated 17
Number of LSA received 98
IPFRR per-prefix tiebreakers:
Name Index
Primary path 20
Node Protecting 30
Interface disjoint 60
Broadcast interface disjoint 70
Downstream path 90
Secondary path 255
LFA termination hold-on timer : 0 secs 600 msecs
Number of areas attached to this router: 2
MemPool - struct ospf lsa : (0-38) | Total (38/100000) blk_size:168
MemPool - struct rxmt : | Total (0/0) blk_size:8
MemPool - OSPF RIB msg4 : | Total (0/0) blk_size:2920
MemPool - OSPF RIB msg4 nh 1 : | Total (0/0) blk_size:24
MemPool - OSPF RIB msg4 nh 2 : | Total (0/0) blk_size:48
MemPool - OSPF RIB msg4 nh 4 : | Total (0/0) blk_size:96
MemPool - OSPF RIB msg4 nh 8 : | Total (0/0) blk_size:192
MemPool - OSPF RIB msg4 nh 16 : | Total (0/0) blk_size:384
MemPool - OSPF RIB msg4 nh 32 : | Total (0/0) blk_size:768
MemPool - OSPF RIB msg4 nh 64 : | Total (0/0) blk_size:1536
MemPool - OSPF RIB msg4 nh 128 : | Total (0/0) blk_size:3072
MemPool - OSPF RIB msg4 nh 255 : | Total (0/0) blk_size:6120
Area 0.0.0.0 (BACKBONE)
Number of interfaces in this area is 2(2)
Number of fully adjacent neighbors in this area is 1
Area has no authentication
SPF algorithm last executed 00:03:05.287 ago
SPF algorithm executed 12 times
Number of LSA 18. Checksum 0x070234
Area 0.0.0.1
Number of interfaces in this area is 1(1)
Number of fully adjacent neighbors in this area is 1
Number of fully adjacent virtual neighbors through this area is 0
Area has no authentication
SPF algorithm last executed 00:03:34.838 ago
SPF algorithm executed 7 times
Number of LSA 18. Checksum 0x09c738
 
R3#
 
 
R3#show ip ospf database router self-originate
 
OSPF Router with ID (1.1.1.3) (Process ID 1 VRF default)
 
Router Link States (Area 0.0.0.0)
 
LS age: 188
Options: 0x22 (-|-|DC|-|-|-|E|-)
Flags: 0x1 : ABR
LS Type: Router-LSA
Link State ID: 1.1.1.3
Advertising Router: 1.1.1.3
LS Seq Number: 8000000b
Checksum: 0x9c4b
Length: 48
Number of Links: 2
 
Link connected to: Stub Network
(Link ID) Network/subnet number: 1.1.1.3
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metric: 65535
 
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.1.3.1
(Link Data) Router Interface address: 10.1.3.2
Number of TOS metrics: 0
TOS 0 Metric: 65535
 
 
Router Link States (Area 0.0.0.1)
 
LS age: 188
Options: 0x22 (-|-|DC|-|-|-|E|-)
Flags: 0x1 : ABR
LS Type: Router-LSA
Link State ID: 1.1.1.3
Advertising Router: 1.1.1.3
LS Seq Number: 8000000c
Checksum: 0xc531
Length: 36
Number of Links: 1
 
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.3.4.2
(Link Data) Router Interface address: 10.3.4.1
Number of TOS metrics: 0
TOS 0 Metric: 65535
 
R3#
 
 
R3#show ip ospf database summary self-originate
 
OSPF Router with ID (1.1.1.3) (Process ID 1 VRF default)
 
Summary Link States (Area 0.0.0.0)
 
LS age: 204
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 10.2.4.0 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 80000009
Checksum: 0x7446
Length: 28
Network Mask: /24
TOS: 0 Metric: 100
 
LS age: 204
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 10.3.4.0 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 80000008
Checksum: 0x6a50
Length: 28
Network Mask: /24
TOS: 0 Metric: 100
 
LS age: 204
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 200.1.1.0 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 80000009
Checksum: 0xf10e
Length: 28
Network Mask: /24
TOS: 0 Metric: 100
 
 
Summary Link States (Area 0.0.0.1)
 
LS age: 204
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 1.1.1.3 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 80000008
Checksum: 0xfaca
Length: 28
Network Mask: /32
TOS: 0 Metric: 100
 
LS age: 203
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 10.1.2.0 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 8000000c
Checksum: 0x902a
Length: 28
Network Mask: /24
TOS: 0 Metric: 100
 
LS age: 204
Options: 0x22 (-|-|DC|-|-|-|E|-)
LS Type: Summary-LSA
Link State ID: 10.1.3.0 (summary Network Number)
Advertising Router: 1.1.1.3
LS Seq Number: 80000008
Checksum: 0x8d30
Length: 28
Network Mask: /24
TOS: 0 Metric: 100
 
R3#
 
Last modified date: 07-13-2023