Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

OSPF questions NSSA area's

The cisco document OSPF NSSA areas doesnt specify that an abr will become a ASBR when NSS area is

configured on it the other router in the NSSA that connects to other AS or redistributes conneced/static also is ASBR.

Comments

###R2 is the internal backbone router

r5Area1<------>#r1Area1-R1Area0#<------>r2<----->#r3Area0-r3Area3#<----->R4a3

Ip address r1 1.1.1.2 ---r2 1.1.1.1

Ip address r2 2.2.2.1 ---r3 2.2.2.2

Ip address r1 5.5.5.1 ---r5 5.5.5.2

Ip address r3 3.3.3.3 ---r4 3.3.3.4

routers R5 LO 192.168.x.x and R4LO 44.44.x.x have loopbacks getting redistributed into OSPF.

R1 did

have a loopback 200.x.x.x which I remove later to stop confusion (RID) when looking at lSA's

At the moment Area 1 and area 3 are NSSA this is the Ip ospf database output from R2 the internal

area backbone router.

#####################################################################

OSPF Router with ID (2.2.2.1) (Process ID 200)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

2.2.2.1 2.2.2.1 1018 0x80000003 0x007408 4

3.3.3.1 3.3.3.1 511 0x80000017 0x0075EC 2

200.200.200.1 200.200.200.1 52 0x8000001C 0x00B010 2

Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

3.3.3.0 3.3.3.1 1023 0x80000011 0x0031A8

5.5.0.0 200.200.200.1 1019 0x8000000D 0x00DD25

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

44.44.0.0 3.3.3.1 464 0x80000001 0x00ED43 0

192.168.0.0 200.200.200.1 32 0x80000001 0x002E9C 0

r2#

Below is the output of the Show ip ospf to verify that these ABR's R1 and R2 become ABR/ASBR's

once NSSA is configuerd on them.

You can see that when their areas 1 and 3 respectivly are configured as NSSA's that they R1 & R2

are indeed no ABR/ASBR's as apposed to just ABR's before.!!!!!!!!!

I only posted R3's output, for the sake of space. r1 is exactly the same!!!

You can also see from the Ip ospf database output above from R2

That their are no ASBR type 4's (summary ASA link states)in the DB.

######

Question ?

as r1 and R3 are now generating the type 5's they are abr/asbr so there is no need to send type 4

to back bone beacuse its now an ABR/asbr that is generating the type 5 is this corrrect ?

In other circumstanes the ABR would do it but when its ABR/ASBR it doesnt need to.

Also the types 5's are advertised by the directly connected routers i.e. R1 and R3 which is

correct....they take the lsa type 7 and pump in lsa type 5's --->BB

hubr3#sh ip ospf

Routing Process "ospf 100" with ID 3.3.3.1

Supports only single TOS(TOS0) routes

Supports opaque LSA

Supports Link-local Signaling (LLS)

####It is an area border and autonomous system boundary router####

Redistributing External Routes from,

Initial SPF schedule delay 5000 msecs

Minimum hold time between two consecutive SPFs 10000 msecs

Maximum wait time between two consecutive SPFs 10000 msecs

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 2. Checksum Sum 0x011BDF

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. 1 normal 0 stub 1 nssa

External flood list length 0

Area BACKBONE(0)

Number of interfaces in this area is 1

Area has no authentication

SPF algorithm last executed 00:00:11.192 ago

SPF algorithm executed 48 times

Area ranges are

Number of LSA 5. Checksum Sum 0x02A8D1

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

Area 3

Number of interfaces in this area is 1

It is a NSSA area

Perform type-7/type-5 LSA translation

Area has message digest authentication

SPF algorithm last executed 00:00:18.484 ago

SPF algorithm executed 50 times

Area ranges are

Number of LSA 7. Checksum Sum 0x02CDAF

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

##################################################################################################

####################

The Areas are no longer NSSA

Link ID ADV Router Age Seq# Checksum

44.44.180.1 3.3.3.1 264 0x80000001 0x009152

192.168.21.50 5.5.5.1 197 0x80000001 0x00EF4B

OSPF Router with ID (2.2.2.1) (Process ID 200)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

2.2.2.1 2.2.2.1 1063 0x80000008 0x0001C1 4

3.3.3.1 3.3.3.1 287 0x80000009 0x008BE6 2

5.5.5.1 5.5.5.1 248 0x80000003 0x00BEB3 2

Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

3.3.3.0 3.3.3.1 1071 0x80000002 0x004F99

5.5.0.0 5.5.5.1 1420 0x80000002 0x000ED3

Summary ASB Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

44.44.180.1 3.3.3.1 264 0x80000001 0x009152

192.168.21.50 5.5.5.1 197 0x80000001 0x00EF4B

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

--->3.3.3.1 44.44.180.1 273 0x80000001 0x008BFC 0

--->44.44.0.0 44.44.180.1 274 0x80000001 0x00B188 0

192.168.0.0 192.168.21.50 219 0x80000001 0x00691D 0

r2#

Question ?

I dont know why I'm getting the first entry under type 5 and not getting one that says adv router

192.168.21.50 with a link Id of 5.5.5.1 as I'm getting two advertised from 44.44.180.1 shouldnt

their be another ?

This is confusing because the only diference in the whole topology is the link from R1--R5 is a

frame-relay point-point wheres the link from r3--R4 is ppp refer to top for router layout this

shouldnt make any difference ?

Why dont I see it ?

Every address is in all routing tables and connectivity if good I can ping 44.44.180.1 from L0

192.168.1.1 in another Area.

And their is no router link state 1.1.1.1 1.1.1.1

which their should be everything is working fine apart form the cosmetic issue any reason why ?

4 REPLIES
Gold

Re: OSPF questions NSSA area's

From what you've written here, I'd say that what you are seeing is the rule that only a single ABR in an NSSA area will do the type 7 to 5 translation. Generally, when an ABR receives a type 7 from an NSSA area, it will check to make certain another ABR isn't translating this same type 7 into a type 5 before doing the translation. The router ID is used to determine which ABR will do the translation.

Russ.W

New Member

Re: OSPF questions NSSA area's

Russ,

I'm sorry your answers are lifeless they have little substance.Your stating the obvious.

Do you try to confuse people.

I'm aware of RID and LSA's etc etc thats not the issue here is it !!!

The link id 1.1.1.1 why isnt this showing up!!!!!

Can you explain this behaviour without going of on another tangent.

The Areas are no longer NSSA a1--a0---a3

Two areas each on different sides of area0 abviously with the same configs apart from IP's the very top of my first post has the topology.

Link ID ADV Router Age Seq# Checksum

44.44.180.1 3.3.3.1 264 0x80000001 0x009152

192.168.21.50 5.5.5.1 197 0x80000001 0x00EF4B

OSPF Router with ID (2.2.2.1) (Process ID 200)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

2.2.2.1 2.2.2.1 1063 0x80000008 0x0001C1 4

3.3.3.1 3.3.3.1 287 0x80000009 0x008BE6 2

5.5.5.1 5.5.5.1 248 0x80000003 0x00BEB3 2

Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

3.3.3.0 3.3.3.1 1071 0x80000002 0x004F99

5.5.0.0 5.5.5.1 1420 0x80000002 0x000ED3

Summary ASB Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

44.44.180.1 3.3.3.1 264 0x80000001 0x009152

192.168.21.50 5.5.5.1 197 0x80000001 0x00EF4B

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

--->3.3.3.1 44.44.180.1 273 0x80000001 0x008BFC 0

--->44.44.0.0 44.44.180.1 274 0x80000001 0x00B188 0

192.168.0.0 192.168.21.50 219 0x80000001 0x00691D 0

r2#

Question ?

I dont know why I'm getting the first entry under type 5 and not getting one that says adv router

192.168.21.50 with a link Id of 5.5.5.1 as I'm getting two advertised from 44.44.180.1 shouldnt

their be another ?

This is confusing because the only diference in the whole topology is the link from R1--R5 is a

frame-relay point-point wheres the link from r3--R4 is ppp refer to top for router layout this

shouldnt make any difference ?

Why dont I see it ?

Every address is in all routing tables and connectivity if good I can ping 44.44.180.1 from L0

192.168.1.1 in another Area.

And their is no router link state 1.1.1.1 1.1.1.1

which their should be everything is working fine apart form the cosmetic issue any reason why ?

New Member

Re: OSPF questions NSSA area's

Good approach dude. Piss people off that are trying to make an honest attempt to help you out. Good luck !

New Member

Re: OSPF questions NSSA area's

Hey Chum !!!

Its called being honest straight up!!!

Hey Buddy Russ has aswered a question for me before and he is very Vague not precise with his answers.

As far as my posts go.

If I were a CCIE that worked at Cisco which obviously I'm not.

I would explain the situation and answer the questions precisly or not at all!!

If i part explained it I would say i dont know why you are experiencing the other issues.If it s causing issues open a TAC case for investigation dah dah dah.

This would be a complete post.

And I'm sure the preson would be very happy with the response for explaining what they new and being honest about the rest.

The question pertaining i.e the link state questions.

Russ did not do this so perhaps in this case he shouldnt bother either that or he misunderstood

I'm the one putting in hours every evening when i get home from work to all hours of the moring and i try to help myself before I ask here believe me!!!

All the info is in my original post with regards to no link state showing up on R1 with a directly connected PPP interface to R2 1.1.1.1 the other serial interface on R2 shows the link state 2.2.2.2

Russ gave an answer about TWO abr's in one NSSA area whats that relate too its not in my post therfor it is completely irellevant isnt it !!!!

And my question was why isnt it showing up.

That question wasnt answered was it ?

I ask you MR CCIE to give me a answer as to why this would happen all routers are the same running the same IOS.

I dont want to be rude its probably frustration.

But you must admit Russ didnt even touch on that question and what he did say wasnt related to anything I said was it.

I dont think he looked at the topology at the top.

I'm sure he's trying to do the right thing but his post didnt help!!!!

R2 has ABR on either side it is an internal backbone router the ABR's are coneected to 1 other router each which is A NSSS ASBR redisributing connected routes area 1 has tw routers and area 3 has two routers The ABR has 2 area 1 obviously connected to the back bone!!!.

Now I redistributed connected on the edge routers which are loacted in different areas on either side of the backbone router R2!! This Made the Abr's ABr/ASBR routers the routers on the edge

that are redidtributing are also ASBR sh ip ospf says this.

What i want to now is related to the output and LSA on R2 the Backbone router.There shouldnt be any more LSA of any description for 1 side or the other the topology is the same.But thsi is not the case.

but the sh ip ospf database is not showing the link state 1.1.1.1 directly connected.

Network connectivity is fine.

This was the question down the bottom of the POST.

And i wanted domeone to help clear this up ....

You saw Russ aswer that question didnt you ?

So buddy "CCIE"I challenge you to Answer the Bottom two questions.

All the output you require is their go on Challenge youself!!!!

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count

2.2.2.1 2.2.2.1 1063 0x80000008 0x0001C1 4

3.3.3.1 3.3.3.1 287 0x80000009 0x008BE6 2

5.5.5.1 5.5.5.1 248 0x80000003 0x00BEB3 2

Summary Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

3.3.3.0 3.3.3.1 1071 0x80000002 0x004F99

5.5.0.0 5.5.5.1 1420 0x80000002 0x000ED3

Summary ASB Link States (Area 0)

Link ID ADV Router Age Seq# Checksum

44.44.180.1 3.3.3.1 264 0x80000001 0x009152

192.168.21.50 5.5.5.1 197 0x80000001 0x00EF4B

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

--->3.3.3.1 44.44.180.1 273 0x80000001 0x008BFC 0

--->44.44.0.0 44.44.180.1 274 0x80000001 0x00B188 0

192.168.0.0 192.168.21.50 219 0x80000001 0x00691D 0

r2#

Question ?

I dont know why I'm getting the first entry under type 5 and not getting one that says adv router

192.168.21.50 with a link Id of 5.5.5.1 as I'm getting two advertised from 44.44.180.1 shouldnt

their be another ?

This is confusing because the only diference in the whole topology is the link from R1--R5 is a

frame-relay point-point wheres the link from r3--R4 is ppp refer to top for router layout this

shouldnt make any difference ?

Why dont I see it ?

Every address is in all routing tables and connectivity if good I can ping 44.44.180.1 from L0

192.168.1.1 in another Area.

And their is no router link state 1.1.1.1 1.1.1.1

which their should be everything is working fine apart form the cosmetic issue any reason why ?

209
Views
0
Helpful
4
Replies
CreatePlease to create content