OSPF Not So Totally Stubby



OSPF Area Types: Not So Totally Stubby

 

This is the last post in a series about OSPF Area Types. Today we’ll go over Not So Totally Stubby Areas. We’ll be using the same topology as the NSSA post, but this time we will inject a specific route (40.40.40.0/24) from the ASBR (R4) instead of a default.
Quick refresher, OSPF Not So Totally Stubby Areas have intra-area routes (Type 2 LSAs) and also external routes in the form of Type 7 LSAs, which are converted to Type 5 LSAs by the ABR. No inter-area routes (Type 3 LSAs) are permitted in a Not So Totally Stubby Area and a default route will be injected by the ABR.
(
Here’s the topology:
I’m not going through the basic OSPF config, so assume everything is configured as the diagram suggests. I’ve redistributed loopbacks on each router (“redistribute connected subnets” under the OSPF process) to give us some external routes, and I added 34.34.34.34/32 to Area 34 so we have an intra-area route to look at. I’ve also added a static route on R4 (40.40.40.0/24) which I’m injecting into OSPF with the “redistribute static subnets” command. Let’s look at some show commands BEFORE we make area 34 a Not So Totally Stubby Area:
First we’ll check out “sh ip route ospf” on R3:
R3#sh ip route ospf
     1.0.0.0/32 is subnetted, 1 subnets
O E2    1.1.1.1 [110/20] via 10.1.123.1, 00:04:20, FastEthernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
O E2    2.2.2.2 [110/20] via 10.1.123.2, 00:04:20, FastEthernet0/0
     4.0.0.0/32 is subnetted, 1 subnets
O E2    4.4.4.4 [110/20] via 10.1.34.4, 00:03:33, Serial0/0
     40.0.0.0/24 is subnetted, 1 subnets
O E2    40.40.40.0 [110/20] via 10.1.34.4, 00:02:57, Serial0/0


Here we see all the loopbacks and the static (40.40.40.0/24) come through as external type 2, which is the default.
Now let’s check out the RIB on R4:
R4#sh ip route
...
Gateway of last resort is not set
     34.0.0.0/32 is subnetted, 1 subnets
O       34.34.34.34 [110/65] via 10.1.34.3, 00:04:51, Serial0/0
     1.0.0.0/32 is subnetted, 1 subnets
O E2    1.1.1.1 [110/20] via 10.1.34.3, 00:04:51, Serial0/0
     2.0.0.0/32 is subnetted, 1 subnets
O E2    2.2.2.2 [110/20] via 10.1.34.3, 00:04:51, Serial0/0
     3.0.0.0/32 is subnetted, 1 subnets
O E2    3.3.3.3 [110/20] via 10.1.34.3, 00:04:51, Serial0/0
     4.0.0.0/32 is subnetted, 1 subnets
C       4.4.4.4 is directly connected, Loopback0
     40.0.0.0/24 is subnetted, 1 subnets
S       40.40.40.0 is directly connected, Null0
     10.0.0.0/24 is subnetted, 2 subnets
C       10.1.34.0 is directly connected, Serial0/0
O IA    10.1.123.0 [110/74] via 10.1.34.3, 00:04:51, Serial0/0

We see one intra-area route (O – LSA 2) to 34.34.34.34/32, one inter-area route (O IA – LSA 3) to 10.1.123.0/23 and three external type 2 (O E2 – LSA 5) routes to the respective loopbacks. Also notice the static (40.40.40.0/24) to null0, which we’re injecting into the OSPF domain.
Now we’ll configure area 34 as not so totally stubby:
R3(config)#router ospf 100
R3(config-router)#area 34 nssa no-summary
 
R4(config)#router ospf 100
R4(config-router)#area 34 nssa
Easy stuff, we configure area 34 with “nssa no-summary” on R3 (ABR), then we configure R4 (ASBR) with “nssa” for area 34.
Let’s examine the new RIB on R4:
R4#sh ip route ospf
     34.0.0.0/32 is subnetted, 1 subnets
O       34.34.34.34 [110/65] via 10.1.34.3, 00:01:50, Serial0/0
     3.0.0.0/32 is subnetted, 1 subnets
O N2    3.3.3.3 [110/20] via 10.1.34.3, 00:01:50, Serial0/0
O*IA 0.0.0.0/0 [110/65] via 10.1.34.3, 00:01:50, Serial0/0
We now have only three OSPF routes, our O (LSA 2) for the 34.34.34.34/32 network, our O*IA default route, which is injected from R3 (ABR) and the N2 (LSA 7) route for R3′s loopback, which is being redistributed with the “redistribute connected subnets” command on R3.
Here’s R4′s OSPF Database:
R4#sh ip ospf d
 
            OSPF Router with ID (4.4.4.4) (Process ID 100)
 
                Router Link States (Area 34)
 
Link ID         ADV Router      Age         Seq#       Checksum Link count
3.3.3.3         3.3.3.3         255         0x80000006 0x00A1D5 3
4.4.4.4         4.4.4.4         252         0x80000009 0x0025E4 2
 
                Summary Net Link States (Area 34)
 
Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         3.3.3.3         272         0x80000001 0x00DE4B
 
                Type-7 AS External Link States (Area 34)
 
Link ID         ADV Router      Age         Seq#       Checksum Tag
3.3.3.3         3.3.3.3         271         0x80000001 0x00E69F 0
4.4.4.4         4.4.4.4         256         0x80000001 0x0090B4 0
40.40.40.0      4.4.4.4         256         0x80000001 0x00A339 0

We see the router LSAs for R3 and R4, which are normal. Next we see the Type 3 LSA for the default route R3 is injecting and finally we see three Type 7 LSAs, one for each external network injected into area 34.
Last we’ll look at R1′s RIB so we can see how Not So Totally Stubby Areas affect the OSPF domain:

R1#sh ip route ospf
     34.0.0.0/32 is subnetted, 1 subnets
O IA    34.34.34.34 [110/11] via 10.1.123.3, 00:14:31, FastEthernet0/0
     2.0.0.0/32 is subnetted, 1 subnets
O E2    2.2.2.2 [110/20] via 10.1.123.2, 00:15:24, FastEthernet0/0
     3.0.0.0/32 is subnetted, 1 subnets
O E2    3.3.3.3 [110/20] via 10.1.123.3, 00:14:31, FastEthernet0/0
     4.0.0.0/32 is subnetted, 1 subnets
O E2    4.4.4.4 [110/20] via 10.1.123.3, 00:05:40, FastEthernet0/0
     40.0.0.0/24 is subnetted, 1 subnets
O E2    40.40.40.0 [110/20] via 10.1.123.3, 00:05:40, FastEthernet0/0
     10.0.0.0/24 is subnetted, 2 subnets
O IA    10.1.34.0 [110/74] via 10.1.123.3, 00:14:31, FastEthernet0/0

The table looks normal. The important thing to note here is that the external routes from R4 are showing up as O E2 (LSA 5s), which we know is caused by R3 converting them from the Type 7s which only exist in NSSAs to Type 5s, which are allowed in normal areas.
Not So Totally Stubby Areas sound odd, and I’ve never seen them in the real world, but they are fair game on the CCIE lab, and you may come across them in a real network. The key concepts are simply that LSA Type 5s are not allowed in Not So Totally Stubby Areas, external routes will show as N (LSA 7s) in the RIB and are converted to Type 5s on the ABR before leaving the area. Also remember that the ABR injects a default route like a normal Totally Stubby Area.

0 comments:

About US

Network Bulls is Best Institute for Cisco CCNA, CCNA Security, CCNA Voice, CCNP, CCNP Security, CCNP Voice, CCIP, CCIE RS, CCIE Security Version 4 and CCIE Voice Certification courses in India. Network Bulls is a complete Cisco Certification Training and Course Coaching Institute in Gurgaon/Delhi NCR region in India. Network Bulls has Biggest Cisco Training labs in India. Network Bulls offers all Cisco courses on Real Cisco Devices. Network Bulls has Biggest Team of CCIE Trainers in North India, with more than 90% of passing rate in First Attempt for CCIE Security Version 4 candidates.
  • Biggest Cisco Training Labs in India
  • More than 90% Passing Rate in First Attempt
  • CCIE Certified Trainers for All courses
  • 24x7 Lab Facility
  • 100% Job Guaranteed Courses
  • Awarded as Best Network Security Institute in 2011 by Times
  • Only Institute in India, to provide CCIE Security Version 4.0 Training
  • CCIE Security Version 4 Training available
  • Latest equipments available for CCIE Security Version 4

Network Bulls Institute Gurgaon

Network Bulls Institute in Gurgaon is one of the best Cisco Certifications Training Centers in India. Network Bulls has Biggest Networking Training and Networking courses labs in North India. Network Bulls is offering Cisco Training courses on real Cisco Routers and Switches. Labs of Network Bulls Institute are 24x7 Available. There are many coaching Centers in Delhi, Gurgaon, Chandigarh, Jaipur, Surat, Mumbai, Bangalore, Hyderabad and Chennai, who are offering Cisco courses, but very few institutes out of that big list are offering Cisco Networking Training on real Cisco devices, with Live Projects. Network Bulls is not just an institute. Network Bulls is a Networking and Network Security Training and consultancy company, which is offering Cisco certifications Training as well support too. NB is awarded in January 2012, by Times, as Best Network Security and Cisco Training Institute for the year 2011. Network Bulls is also offering Summer Training in Gurgaon and Delhi. Network Bulls has collaboration with IT companies, from which Network Bulls is offering Networking courses in Summer Training and Industrial Training of Btech BE BCA MCA students on real Live projects. Job Oriented Training and Industrial Training on Live projects is also offered by network bulls in Gurgaon and Delhi NCR region. Network Bulls is also providing Cisco Networking Trainings to Corporates of Delhi, Gurgaon, bangalore, Jaipur, Nigeria, Chandigarh, Mohali, Haryana, Punjab, Bhiwani, Ambala, Chennai, Hyderabad.
Cisco Certification Exams are also conducted by Network Bulls in its Gurgaon Branch.
Network Bulls don't provide any Cisco CCNA, CCNP simulations for practice. They Provide High End Trainings on Real topologies for high tech troubleshooting on real Networks. There is a list of Top and best Training Institutes in India, which are providing CCNA and CCNP courses, but NB has a different image from market. Many students has given me their feedbacks and reviews about Network bulls Institute, but there were no complaints about any fraud from this institute. Network Bulls is such a wonderful place to get trained from Industry expert Trainers, under guidance of CCIE Certified Engineers.

About Blog

This Blog Contains Links shared by sites: Cisco Guides, Dumps collection, Exam collection, Career Cert, Ketam Mehta, GodsComp.co.cc.

NB

NB
Cisco Networking Certifications Training

Cisco Training in Delhi

ccna training in gurgaon. ccnp course institute in gurgaon, ccie coaching and bootcamp training near gurgaon and delhi. best institute of ccna course in delhi gurgaon india. network bulls provides ccna,ccnp,ccsp,ccie course training in gurgaon, new delhi and india. ccsp training new delhi, ccie security bootcamp in delhi.

Testimonials : Network Bulls

My Name is Rohit Sharma and i Have done CCNA and CCNP Training in Gurgaon Center of Network Bulls and it was a great experience for me to study in Network Bulls.

Cisco Networking Certifications

Myself Komal Verma and i took CCSP Training from Network Bulls in Gurgaon. The day i joined Network Bulls, the day i get addicted with Networking Technologies and I thank Mr. Vikas Sheokand for this wonderful session of Networking. :)
I must say that Network Bulls is Best Institute of CCNA CCNP CCSP CCIE Course Training in Gurgaon, New Delhi and in India too.
Komal Verma

About a wonderfull CCIE Training Institute in Gurgaon

I am Kiran shah from New Delhi. I have recently completed my CCNA CCNP & CCIE Training in Gurgaon from Network Bulls and i recommend Network Bulls for Cisco Training in India.

Kiran Shah

Cisco Coaching and Learning Center

Disclaimer: This site does not store any files on its server. I only index and link to content provided by other sites. If you see any file on server that is against copy right you can inform me at (sidd12341 [at] gmail.com). I will delete that materials within two days. This Website is not official Website of any Institute like INE, Network Bulls, IP Expert. Thanks

CCIE Security Version 4

Cisco Finally updated CCIE Security Lab exam blueprint. WSA Ironport and ISE devices are added in CCIE Security Version 4 Lab Exam Syllabus Blueprint. In Updated CCIE Security Version 4 Syllabus blueprint, new technologies like Mobile Security, VoIP Security and IPV6 Security along with Network Security, are added. As in CCIE Security Version 3 blueprint, Cisco had focused on Network Security only, but now as per market demand, Cisco is looking forward to produce Internet gear Security Engineer, not only Network Security engineers.
In CCIE Security Version 4 Bluerpint, Lab Exam is going to be more interested than before. What is Difference in CCIE Security Version 3 and Version 4? Just go through the CCIE Security Version 4 Lab Equipment and Lab Exam Syllabus Blueprints and find out!