OSPF (Open Shortest Path first)
Mitrabh Shukla
National IP Manager
2 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What Are Some Tips for Deployment?
How Do I Configure OSPF?
How Do I Verify OSPF ?
3 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Why Is It Called a Link State Protocol?
specific link characteristics and state information
4 © Nokia Siemens Networks MPLS / Mitrabh Shukla
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Link State Protocol Operation
Topology Information Is
Kept in a Database
Separate from the Routing
Table
A
B
C
2
13
13
Q
Z
X
X’s Link State
Z
X
YQ
Z’s Link State
Q’s Link State
5 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Advantages of a Link State Protocol
Uses costs to calculate path
Typically displays faster convergence than distance vector routing protocols
Typically more scalable due to hierarchical nature
6 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF Benefits
Uses metrics—path cost
Support for CIDR, VLSM, authentication, multipath, and IP unnumbered
Relatively low, steady state bandwidth requirements
7 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF History
Development began 1987 by IETF
OSPFv2 established in 1991 with RFC 1247
Goal—a link state protocol more efficient and scaleable than RIP
Latest revision is RFC 2328 April 1998
8 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What are some tips for Deployment?
How do I configure OSPF?
How do I verify OSPF ?
9 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF Functions and Definitions
The high-level function of OSPF is
• Discover neighbors and form adjacencies
• Flood Link State Database (LSDB) information
• Compute the shortest path
• Install routes in route forwarding table
This section expands on these functions
Some definitions are needed first
• (See text on the page with this slide)
10 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Let’s exchange information
Discovering Adjacent Neighbors
Discover neighbors with Hello packets
Form Adjacencies with appropriate neighbors
Exchange Link State Database (LSDB) information using Link State Advertisements (LSA)
Hello, I’m B
Hello, I’m A
RID A RID B
I know about these links…
OK
I know about these links…
11 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Adjacency States
Sample Log showing adjacency processP1R1(config-router)#log-adjacency-changes detail
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from DOWN to INIT, Received Hello
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from INIT to 2WAY, 2-Way Received
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from 2WAY to EXSTART, AdjOK?
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from EXSTART to EXCHANGE, Negotiation Done
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from EXCHANGE to LOADING, Exchange Done
6d04h: %OSPF-5-ADJCHG: Process 100, Nbr 10.131.63.251 on
FastEthernet0/0 from LOADING to FULL, Loading Done
12 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Propagate changes to maintain Link State Database synchronization
Flooding can impact performance in large nets
Keep LSDB small!
Flooding Link State Advertisements
Animated
13 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Computing the Shortest Path Tree
The optimal path is determined by thesum of the interface costs: Cost = 108/BW
10
192.213.11.0
222.211.10.0
128.213.0.0
8
10
5
5
10
5
192.213.11.0
222.211.10.0
128.213.0.0
10
10
10
5
5
0
5
Actual Network Shortest Path Tree
14 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Routing TableUpdated
Routing Table
Dijkstra Algorithm
Link State Database
Router 2, Area 1
LSA
ACK
Router 1, Area 1
When a Link Changes State
Every router in an area hears a specific link LSA
Each router computes shortest path routing table
15 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF Areas
Area 10
RIP/RIPv2 World
Area 0
Area 11
Area 12
Area is a group of contiguous hosts and networks
Each area has a topology database
• Invisible outside the area
• Reduction in routing traffic
Backbone area must be contiguous
• All other areas must connect to the backbone
Virtual Links
Area 13
16 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
What Are Virtual Links?
All areas must connect to area 0.0.0.0
Not recommended — So what’s it for?
• Tunnel ABR summaries to area 0
• Allow areas to connect to areas other than 0
• Repair a discontinuous area 0 (for example, if two companies merge and have backbones)
AREA 20AREA 10 AREA 0
17 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Router Types and Location
Autonomous System Boundary Routers
(ASBR) bordering a ―non-OSPF‖ area
Area Border Routers
Between areasRIP/RIPv2
Network
Area 10
Area 0
Area 11
Area 12
Area 13
Internal Router (IR)
Inside an area
Backbone Router (BR)
Inside the core
18 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VERSION | TYPE | LENGTH
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ROUTER ID
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AREA ID
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CHECKSUM | AuTYPE
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
AUTHENTICATION
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
DATA
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OSPF Routing Protocol Packets
Share a common protocol header
Routing protocol packets are sent withtype of service (TOS) of 0
5 types of routing protocol packets (see text)
19 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Common Types of Link State Advertisements (LSAs)
Router link (LSA type 1)
Network link (LSA type 2)
Network summary (LSA type 3)
ASBR Summary (LSA type 4)
External (LSA type 5)
NSSA external (LSA type 7)
20 © Nokia Siemens Networks MPLS / Mitrabh Shukla
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Opaque Link State Advertisements (LSAs)
RFC 2370
• Used for distribution for applications
Opaque link-local (LSA type 9)
Opaque area-local (LSA type 10)
• First Cisco implementation with RSVP
Opaque AS (LSA type 11)
• Similar to type 5
21 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
RIP Network
Simplified Example of Different LSAs
RIP Network
Area 10
Area 0
Area 11
External (type 5)
ASBR IR
ABR
ASBR
ABR
DR
ABR Summary (type 3)
IR ABR IR
Router link (type 1)
IR IR
External
ASBRExternal (type 7)
ASBR IR
(only in NSSA)
Animated
Network link (type 2)
DR IR
ASBR Summary (type 4)
ABR IR (about ASBR)ASBR
Note: only one example of each LSA type
exchange is demonstrated in this graphic
22 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
DRBDR
DRBDR
Multi-Access Media
Gig/Fast/Ethernet, FDDI, Token Ring
Multicast
DR and BDR for each network
23 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Uses IP Multicast for Sending/Receiving Updates
On Broadcast networks
• DR and BDR —> AllSPFRouters (224.0.0.5)
• All other routers —> AllDRRouters (224.0.0.6)
Hello packets sent to All SPFRouters (Unicast on point-to-point and virtual links)
24 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What Are Some Tips for Deployment?
How Do I Configure OSPF?
How Do I Verify OSPF ?
25 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Backbone
Router
Using Areas
Area 1
Area 4
Area 0
Area 2 Area 3
Internal
Router
Area
Border
Router
Autonomous
System (AS)
Border Router
Internet
26 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Regular Area Flooding
Backbone Area 0
x.x.x.1
2.x.x.x
3.x.x.x
External
X.X.X.1
TokenRing
TokenRing
3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
2.2.4.0
2.2.4.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
TokenRing
TokenRing
1.1.4.0
1.1.4.0
1.1.3.0
1.1
.1.0
x.x.x.1
1.x.x.x
2.x.x.x
x.x.x.1
1.x.x.x
3.x.x.x
ASBR
x.x.x.1
27 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Stub Area Flooding
Backbone Area 0
Default
2.x.x.x
3.x.x.x
External
X.X.X.1
TokenRing
TokenRing
3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
2.2.4.0
2.2.4.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
TokenRing
TokenRing
1.1.4.0
1.1.4.0
1.1.3.0
1.1
.1.0
x.x.x.1
1.x.x.x
2.x.x.x
x.x.x.1
1.x.x.x
3.x.x.x
ASBR
x.x.x.1
28 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Totally Stubby Area Flooding
Backbone Area 0
Default
External
X.X.X.1
TokenRing
TokenRing
3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
2.2.4.0
2.2.4.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
TokenRing
TokenRing
1.1.4.0
1.1.4.0
1.1.3.0
1.1
.1.0
x.x.x.1
1.x.x.x
2.x.x.x
x.x.x.1
1.x.x.x
3.x.x.x
ASBR
x.x.x.1
area x stub no-summary
area x stub
29 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Not So Stubby Areas (NSSA) Flooding
Backbone Area 0
External
X.X.X.1
TokenRing
TokenRing
3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
2.2.4.0
2.2.4.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
TokenRing
TokenRing
1.1.4.0
1.1.4.0
1.1.3.0
1.1
.1.0
Default
x.x.x.1
x.x.x.2
1.x.x.x
2.x.x.x
Default
x.x.x.1
x.x.x.2
1.x.x.x
3.x.x.x
ASBR
x.x.x.1
External
X.X.X.2
x.x.x.2
x.x.x.2
LSA Type
Default must be
manually configured
Default
2.x.x.x
3.x.x.x
30 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Summarization
Route summarization is the consolidation of advertised addresses
Instead of advertising many specific prefixes, advertise only one summary prefix
• Area range command on ABR to summarize type 3 LSAs
• Summary-address command on ASBR to summarize type 5 LSAs
LSDB is smaller and more stable
Drawback is possible suboptimal routing
31 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Inter-Area Route Summarization - Area Range
ABRs will advertise networks in one area into another area
By default ABRs do not always summarize routes between areas
Advertise a summary route that covers as many individual networks within the area as possible (requires good address design)
On the ABR (Summarizes routes before injecting them into different area)
• Router(config-router)#area <area-id> range<network-address> <subnet-mask>
32 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
External Route Summarization - summary-address
Each route, redistributed into OSPF from other protocols, is advertised individually with an external link state advertisement (LSA)
To reduce the size of the OSPF link state database configure a summary for external routes that are covered by a specified network address and mask
On the ASBR only (Summarizes external routes before injecting them into the OSPF domain)
• Router(config-router)# summary-address <network-address> <subnet-mask>
33 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Not Summarized: Specific Links
Backbone
Area 0
2.2.2.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
1.1
.1.0
1.1.2.0 1.1.3.0
TokenRing
1.1.4.0
TokenRing
TokenRing
TokenRing 3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
1.1.1.0
1.1.2.0
1.1.3.0
1.1.4.0
3.3.1.0
3.3.2.0
3.3.3.0
3.3.4.0
2.2.1.0
2.2.2.0
2.2.3.0
Normal LSA flooding across area boundaries
Link state changes propagate out
34 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
2.2.2.0
2.2.3.0
2.2
.1.0
TokenRing
TokenRing
Summarized: Summary Links
Only summary LSA flooding across area boundaries
Link-state changes NOT propagated out
Backbone
Area 0
1.1
.1.0
1.1.2.0 1.1.3.0
TokenRing
1.1.4.0
TokenRing
TokenRing
TokenRing 3.3.4.0
3.3.4.0
3.3.3.0
3.3
.1.0
1.0.0.0
2.0.0.0
3.0.0.0
35 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Area 0If R1 and R1 advertise the 11.1/16 subnet into area 0, suboptimal routing could occur
Use the area range command and divide the /16 into two /17s
Configure on Both ABRs
• area 10 range 11.1.0 /17
area 10 range 11.1.128 /17
Cost to Range 1:
• Via ABR1: 30 (R1-R3-R5) Via ABR2: 60 (R2-R4-R5)
Cost to Range 2:
• Via ABR1: 60 (R1-R3-R6) Via ABR2: 30 (R2-R4-R6)
11.1/16
ABR1 ABR2
10
505020 20
11.1.1/24
11.1.2/24 11.1.130/24
11.1.129/24
10
Preventing Suboptimal Summarization
R6
Area 10R4
R2R1
R3
R5
Range 2Range 1
36 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Area 3
network 131.108.0.0
subnets 49-63
range 255.255.240.0
Area 1
network 131.108.0.0
subnets 17-31
range 255.255.240.0
Area 2
network 131.108.0.0
subnets 33-47
range 255.255.240.0
Area 0
network 192.117.49.0
range 255.255.255.0
Addressing
Assign contiguous ranges of subnets per area to facilitate summarization
37 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What Are Some Tips for Deployment?
How do I configure OSPF?
How do I verify OSPF ?
38 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
IP Backbone
USA
FranceGermany
Japan
OSPF 1
BGP 1
Brazil Canada
OSPF 1
BGP 1
OSPF 1
BGP 1OSPF 1
BGP 1
OSPF 1
BGP 1
OSPF 1
BGP 1OSPF 1
BGP 1
Service Provider Deployment Characteristics
SPs will have only one instance of IGP running throughout network
BGP carries external reachability
No Redistribution
39 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Service Provider OSPF Features
OSPF features ISPs should consider
• OSPF logging neighbor changes
• OSPF reference cost
• OSPF Router ID Command
• OSPF Process Clear/Restart
• OSPF Authentication
40 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What Are Some Tips for Deployment?
How Do I Configure OSPF?
How Do I Verify OSPF ?
41 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Configure OSPF Steps
Configure OSPF Process
• Enable OSPF routing, which places you in router configuration mode
– router OSPF process-id
Define networks to advertise
• Network Statement or Redistribution
Configure OSPF Interfaces
42 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF - Adding Networks(Specific Network Statements)
Specific network statements
• Every interface participating in OSPF requires a network statement
– router OSPF 100
– network 192.168.1.1 0.0.0.3 area 51
– network 192.168.1.5 0.0.0.3 area 51
43 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF - Adding Networks(Redistribution)
redistribute connected subnets
• Works for all connected interfaces on the router but networks are not summarized
– router OSPF 100
– redistribute connected subnets
Not recommended
44 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Router Sub-commands
NETWORK <n.n.n.n> <mask> AREA <area-id>
AREA <area-id> STUB {no-summary}
AREA <area-id> AUTHENTICATION
AREA <area-id> DEFAULT_COST <cost>
AREA <area-id> VIRTUAL-LINK <router-id>...
AREA <area-id> RANGE <address mask>
45 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF - Passive Interface
For interfaces that should not participate in OSPF set them as passive
– router OSPF 100
– passive-interface Serial 1/0
46 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF - Default Passive Interface
Sets all interfaces as passive by default
Activate interfaces that need to have adjacencies set
• router OSPF 100
• passive-interface default
• no passive-interface POS 4/0
47 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF - Virtual Links
The virtual link is between router ID 1.1.1.1 and router ID 2.2.2.2
on router 1.1.1.1 – area 10 virtual-link 2.2.2.2
on router 2.2.2.2
• area 10 virtual-link 1.1.1.1
AREA 20AREA 0AREA 10
48 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Interface Subcommands
IP OSPF COST <cost>
IP OSPF PRIORITY <8-bit-number>
IP OSPF HELLO-INTERVAL <number-of-seconds>
IP OSPF DEAD-INTERVAL <number-of-seconds>
IP OSPF AUTHENTICATION-KEY <8-bytes-of-password>
49 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Agenda
What is a Link State Protocol?
How Does OSPF Work?
How Do I Scale OSPF?
What Are Some Tips for Deployment?
How Do I Configure OSPF?
How Do I Verify OSPF ?
50 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Verify Configuration
P1R1#show ip protocols
Routing Protocol is "ospf 100"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Router ID 10.131.31.251
It is an area border router
Number of areas in this router is 2. 2 normal 0 stub 0 nssa
Maximum path: 4
Routing for Networks:
10.131.31.224 0.0.0.3 area 0
10.131.31.228 0.0.0.3 area 110
10.131.31.240 0.0.0.3 area 0
10.131.31.251 0.0.0.0 area 0
10.131.255.224 0.0.0.3 area 0
Passive Interface(s):
Ethernet2/0
Ethernet3/0
Loopback0
Routing Information Sources:
Gateway Distance Last Update
10.131.31.251 110 00:00:13
Distance: (default is 110)
51 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF Verification (Routes)
Are routes getting old?
• show ip route
• OSPF routes should get old
Is the number of routes stable?
• If you have the luxury, fail a link, allow the network to converge then restore the link and let the network converge
– Are convergence times appropriate for the protocol
– Remember to account for differentials in convergence time
52 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip route ospf
P1R1#show ip route ospf
10.0.0.0/8 is variably subnetted, 24 subnets, 4 masks
O IA 10.131.63.254/32 [110/31] via 10.131.31.226, 2d19h, E1/0
O IA 10.131.63.252/32 [110/21] via 10.131.31.226, 2d19h, E1/0
O IA 10.131.63.253/32 [110/31] via 10.131.31.226, 2d19h, E1/0
O 10.131.63.251/32 [110/11] via 10.131.31.226, 2d19h, E1/0
O IA 10.131.63.228/30 [110/20] via 10.131.31.226, 2d19h, E1/0
O 10.131.63.224/30 [110/20] via 10.131.31.226, 2d19h, E1/0
O IA 10.131.63.236/30 [110/30] via 10.131.31.226, 2d19h, E1/0
O IA 10.131.63.232/30 [110/30] via 10.131.31.226, 2d19h, E1/0
O 10.131.31.254/32 [110/21] via 10.131.31.230, 2d19h, E0/0
O 10.131.31.252/32 [110/11] via 10.131.31.230, 2d19h, E0/0
O IA 10.131.31.253/32 [110/21] via 10.131.31.230, 2d19h, E0/0
O 10.131.31.236/30 [110/20] via 10.131.31.230, 2d19h, E0/0
O IA 10.131.31.232/30 [110/20] via 10.131.31.230, 2d19h, E0/0
O 10.131.223.240/30 [110/20] via 10.131.31.226, 2d19h, E1/0
AGE
53 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
OSPF Verification (neighbors)
Do I have all the neighbors I should have?
Are neighbors in the ―FULL‖ state?
P1R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.131.63.251 1 FULL/DR 00:00:37 10.131.31.226 E1/0
10.131.31.252 1 FULL/DR 00:00:31 10.131.31.230 E0/0
54 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Other OSPF Show Commands
show ip OSPF
show ip OSPF interface
show ip OSPF database
show ip OSPF virtual-links
show ip OSPF border-routers
show ip OSPF flood-list
show ip OSPF request-list
show ip OSPF retransmission-list
show ip OSPF summary-address
55 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip ospf (1 of 2)
P1R1#sh ip ospf
Routing Process "ospf 100" with ID 10.131.31.251
Supports only single TOS(TOS0) routes
Supports opaque LSA
It is an area border router
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 2. 2 normal 0 stub 0 nssa
External flood list length 0
56 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip ospf (2 of 2)
Area BACKBONE(0)
Number of interfaces in this area is 5
Area has no authentication
SPF algorithm executed 5 times
Area ranges are
Number of LSA 27. Checksum Sum 0x0D12B3
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 14
Flood list length 0
Area 110
Number of interfaces in this area is 1
Area has no authentication
SPF algorithm executed 4 times
Area ranges are
Number of LSA 38. Checksum Sum 0x126275
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
57 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF interface
P1R1#show ip OSPF interface
Ethernet2/0 is up, line protocol is up
Internet Address 10.131.255.226/30, Area 0
PID 100, Router ID 10.131.31.251, Net Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 10.131.31.251, address 10.131.255.226
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
No Hellos (Passive interface)
Index 5/6, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Loopback0 is up, line protocol is up
Internet Address 10.131.31.251/32, Area 0
PID 100, Router ID 10.131.31.251, Net Type LOOPBACK, Cost: 1
Loopback interface is treated as a stub Host
===========================snip===============================
58 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF database
P1R1#show ip OSPF database
OSPF Router with ID (10.131.31.251) (Process ID 100)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link
count
10.131.31.251 10.131.31.251 1872 0x80000060 0x00DF2F 5
10.131.31.252 10.131.31.252 1 (DNA) 0x80000002 0x00B0E3 1
===========================snip==============================Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.131.31.226 10.131.63.251 107 0x8000005F 0x0040D4
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.131.31.228 10.131.31.251 1872 0x80000060 0x00F0AB
10.131.31.228 10.131.31.252 5 (DNA) 0x80000001 0x00A951
===========================snip==============================Summary ASB Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.131.31.252 10.131.31.251 1876 0x8000005E 0x00087A
10.131.63.252 10.131.63.251 110 0x8000005F 0x00C37D
Continues with other areas
59 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF virtual-links
P1R1#show ip OSPF virtual-links
Virtual Link OSPF_VL0 to router 10.131.31.252 is up
Run as demand circuit
DoNotAge LSA allowed.
Transit area 110, via interface Ethernet0/0, Cost of using 10
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:06
Adjacency State FULL (Hello suppressed)
Index 2/3, retransmission queue length 0, number of retransmission
2
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 1, maximum is 1
Last retransmission scan time is 0 msec, maximum is 0 msec
60 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
Chapter Summary
You should now be able to:
Describe the functional characteristics of OSPF
Discuss OSPF scalability practices
Configure basic OSPF routing
Configure OSPF areas
Verify OSPF functionality
61 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF flood-list
P1R1#show ip OSPF flood-list
OSPF Router with ID (10.131.31.251) (Process ID 100)
Interface Ethernet2/0, Queue length 0
Interface Loopback0, Queue length 0
Interface Ethernet3/0, Queue length 0
Interface Ethernet1/0, Queue length 0
Interface Ethernet0/0, Queue length 0
62 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF request-list
P1R1#show ip OSPF request-list
OSPF Router with ID (10.131.31.251) (Process ID 100)
Neighbor 10.131.63.251, interface E1/0 address 10.131.31.226
Type LS ID ADV RTR Seq NO Age Checksum
Neighbor 10.131.31.252, interface E0/0 address 10.131.31.230
Type LS ID ADV RTR Seq NO Age Checksum
63 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF retransmission-list
P1R1#show ip OSPF retransmission-list
OSPF Router with ID (10.131.31.251) (Process ID 100)
Neighbor 10.131.63.251, interface E1/0 address 10.131.31.226
Neighbor 10.131.31.252, interface E0/0 address 10.131.31.230
64 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF summary-address
P1R1#show ip OSPF summary-address
OSPF Process 100, Summary-address
Not configured
65 © Nokia Siemens Networks MPLS / Mitrabh Shukla
For internal use
show ip OSPF border-routers
P1R1#show ip OSPF border-routers
OSPF Process 100 internal Routing Table
Codes: i - Intra-area route, I - Inter-area route
i 10.131.63.251 [10] via 10.131.31.226, E1/0, ABR, Area 0, SPF 5
i 10.131.63.252 [20] via 10.131.31.226, E1/0, ABR/ASBR, Area 0, SPF 5
i 10.131.31.252 [10] via 10.131.31.230, E0/0, ABR/ASBR, Area 0, SPF 5
i 10.131.31.252 [10] via 10.131.31.230, E0/0, ABR/ASBR, Area 110, SPF 4
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