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Issue NSSA like ASBR with Default Route

Created: Apr 13, 2020 16:59:12Latest reply: Apr 22, 2020 07:11:44 775 15 0 0 0
  Rewarded HiCoins: 0 (problem resolved)

Dear Community,


In these days i'm make some labs to refresh my knowledge on OSPF unfortunately i have the issue on NSSA ABR in specific scenario.


I have2 Area


AREA 0 (Backbone) AREA 1 ( NSSA )


R1 is in AREA 0

R2 is ABR with Interface gi0/0/0 in AREA 0 and gi0/0/1 in AREA1

R3 is in AREA 1

R4 is ASBR in AREA 1


the configuration under ospf 1 process on the ABR and ASBR is the same


R2 ABR

ospf 1

area 0.0.0.1

nssa


R3 NSSA Router

ospf 1

area 0.0.0.1

nssa


R4 ASBR

ospf 1

area 0.0.0.1

nssa


now, in R3 and R4  receive the default route automatically generated by ABR without issue, i already tried to import the static route

on the R4 with success, all networks are reacheable from all routers.

Now i tried to use the ASBR to redistribute the default route to simulate the internet connession

the configuration changes on the R4 like below



ospf 1

area 0.0.0.1

nssa default-route-originate


ip route 0.0.0.0 0.0.0.0 x.x.x.x


unfortunately the default route originated from R2 (ABR) wins on R3, therefore it forward the packet to "internet" to R2 and discard the traffic.

Could you remember me if there is some limitations about this configuration?

let me know


Best regards


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Featured Answers
chenhui
Admin Created Apr 22, 2020 06:51:57

Posted by rcavezzale at 2020-04-21 22:28 Sorry sapte :( In these day I have some problem I share with you ASAP
I think in your situation, all work fine as expected. I'm not sure if you are trying to get the ABR to advertise a LSA type 3 default route into the NSSA area.
Kindly let us know if I understand your thoughts correctly.
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rcavezzale
rcavezzale Created Apr 22, 2020 08:54:52 (0) (0)
No i cannot try to generate or advertise LSA type 3 in NSSA area.
My goal is advertise the default router type 7 from the ASBR and translate it from the ABR in type 5 to Area 0

after many tentative i think that is not possible.  
All Answers
DDSN
DDSN Admin Created Apr 14, 2020 02:16:20

Hi,rcavezzale
OSPF default routes are used in the following situations:
An ABR advertises Type 3 LSAs to instruct routers in the same area to forward packets between areas.
ASBRs advertise Type 5 LSAs or Type 7 LSAs to instruct routers in the OSPF routing domain to forward packets outside the OSPF routing domain.
The preference of the default route in Type 3 LSAs is higher than that of the route in Type 5 or Type 7 LSAs.
Therefore, on R3, the default route of R2 is preferred.
I hope it helps!
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Sapte
Sapte Created Apr 14, 2020 09:38:06


hi @rcavezzale

A router in an OSPF domain receives default route informations from differet respectively LSA3 >LSA 5 or 7

In order to solve your problem you should use use " nssa no-summary" command instead "nssa" in routers
Totally NSSA will remove the Type 3 LSAs,so there will be just LSA Type 1,2 and 7

Test and inform us please

Have a nice day
and your ABR will change LSA Type 7 to LSA Type 5
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rcavezzale
rcavezzale Created Apr 14, 2020 11:06:54

Thanks for response, but I wanted to knew if there is one method to use the normal NSSA, unfortunately , from yours feedbacks there is no.


I'm checking with Huawei HCIE v3.0 official documentation, at page 224 there is a summary of the area types, under NSSA  and Totally NSSA is written:


NSSA:


an ABR automatically generates a default type 7 LSA and advertises it whitin the entire NSSA.


Manually configure ASBR to generate a type 7 LSA and advertises it whitin the entire NSSA.


Totally NSSA:


 an ABR automatically generates a default type 3 LSA and advertises it whitin the entire NSSA.


in my case on NSSA area, ABR generate the default route with LSA 7, infact in database DB on all router i shows NSSA 0.0.0.0 x.x.x.x.

futherover in routing table the tag is O_NSSA.


when I try to generate the defaul route from R4 (ASBR)... in routing table of all routers NSSA except R2, I shows both defaults with precedence 150 e cost 1 type external 2


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chenhui
chenhui Admin Created Apr 15, 2020 02:49:59

Posted by rcavezzale at 2020-04-14 11:06 Thanks for response, but I wanted to knew if there is one method to use the normal NSSA, unfortunate ...
Hi,
I'm not clear what you mean use the normal NSSA, maybe you are available to explain that.
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rcavezzale
rcavezzale Created Apr 15, 2020 12:24:31 (0) (0)
Normale NSSA = NSSA  
Sapte
Sapte Created Apr 15, 2020 11:55:05

Hi @rcavezzale


Which command do you use for creation default route,i think you refer about cisco command,you can use nssa command for huawei to advertise default route if there is

Also you can advertse default-route by default-route-advertise command

As another question can you please share with us whole configuration in your routers and ping & trace test result

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rcavezzale
rcavezzale Created Apr 15, 2020 12:51:58


Configuration ABR:

[NSSA_ABR]disp c c ospf
[V200R003C00]
#
ospf 1 
 area 0.0.0.0 
  network 10.0.0.0 0.255.255.255 
 area 0.0.0.1 
  network 192.168.0.0 0.0.255.255 
  nssa
#


Output Command ABR:

[NSSA_ABR]disp ip routing-table protocol ospf
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : OSPF
         Destinations : 1        Routes : 1        
OSPF routing table status : <Active>
         Destinations : 1        Routes : 1
Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface
        1.1.1.1/32  O_NSSA  150  101         D   192.168.2.5     GigabitEthernet
0/0/1
OSPF routing table status : <Inactive>
         Destinations : 0        Routes : 0
[NSSA_ABR]disp ospf lsdb
 OSPF Process 1 with Router ID 10.1.2.2
 Link State Database 
         Area: 0.0.0.0
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    10.1.2.2        10.1.2.2            13  36    8000008B       1
 Router    10.1.2.1        10.1.2.1            15  36    80000060       1
 Network   10.1.2.1        10.1.2.1            15  32    80000007       0
 Sum-Net   192.168.2.0     10.1.2.2            14  28    80000050       1
 
         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    192.168.2.3     192.168.2.3         21  36    80000310       1
 Router    192.168.2.5     192.168.2.5         23  36    800002DB       1
 Router    192.168.2.4     192.168.2.4         25  36    8000047B       1
 Router    10.1.2.2        10.1.2.2            22  36    8000018B       1
 Network   192.168.2.5     192.168.2.5         23  40    80000024       0
 Sum-Net   10.1.2.0        10.1.2.2            42  28    80000034       1
 NSSA      0.0.0.0         10.1.2.2            14  36    80000001       1
 NSSA      0.0.0.0         192.168.2.5        589  36    80000056       1
 NSSA      1.1.1.1         192.168.2.5       1512  36    80000033     100
 
 AS External Database
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 External  1.1.1.1         10.1.2.2            14  36    80000006     100


Configuration ASBR:


[NSSA_ASBR]disp c c ospf
#
ospf 1
 import-route static cost 100 type 1
 area 0.0.0.1
  network 192.168.0.0 0.0.255.255
  nssa default-route-advertise
#


Output Command ASBR:


[NSSA_ASBR]disp ospf lsdb
 OSPF Process 1 with Router ID 192.168.2.5
 Link State Database 
         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    192.168.2.3     192.168.2.3        548  36    80000310       1
 Router    192.168.2.5     192.168.2.5        550  36    800002DB       1
 Router    192.168.2.4     192.168.2.4        553  36    8000047B       1
 Router    10.1.2.2        10.1.2.2           551  36    8000018B       1
 Network   192.168.2.5     192.168.2.5        550  40    80000024       0
 Sum-Net   10.1.2.0        10.1.2.2           571  28    80000034       1
 NSSA      0.0.0.0         192.168.2.5       1116  36    80000056       1
 NSSA      1.1.1.1         192.168.2.5        239  36    80000034     100
 NSSA      0.0.0.0         10.1.2.2           543  36    80000001       1
 
[NSSA_ASBR]disp ip routing pro ospf
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : OSPF
         Destinations : 1        Routes : 1        
OSPF routing table status : <Active>
         Destinations : 1        Routes : 1
Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface
       10.1.2.0/24  OSPF    10   2           D   192.168.2.2     GigabitEthernet
0/0/1
OSPF routing table status : <Inactive>
         Destinations : 0        Routes : 0


Configuration NSSA ROUTER:


[NSSA_ROUTER]disp c c ospf
#
ospf 1
 area 0.0.0.1
  network 192.168.0.0 0.0.255.255
  nssa
#


Output Command NSSA ROUTER:


[NSSA_ROUTER]disp ospf lsdb 
 OSPF Process 1 with Router ID 192.168.2.4
 Link State Database 
         Area: 0.0.0.1
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric
 Router    192.168.2.3     192.168.2.3        656  36    80000310       1
 Router    192.168.2.5     192.168.2.5        659  36    800002DB       1
 Router    192.168.2.4     192.168.2.4        660  36    8000047B       1
 Router    10.1.2.2        10.1.2.2           659  36    8000018B       1
 Network   192.168.2.5     192.168.2.5        659  40    80000024       0
 Sum-Net   10.1.2.0        10.1.2.2           680  28    80000034       1
 NSSA      0.0.0.0         192.168.2.5       1225  36    80000056       1
 NSSA      0.0.0.0         10.1.2.2           651  36    80000001       1
 NSSA      1.1.1.1         192.168.2.5        348  36    80000034     100
 
[NSSA_ROUTER]disp ip routin pro ospf
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Public routing table : OSPF
         Destinations : 3        Routes : 4        
OSPF routing table status : <Active>
         Destinations : 3        Routes : 4
Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface
        0.0.0.0/0   O_NSSA  150  1           D   192.168.2.5     GigabitEthernet
0/0/1
                    O_NSSA  150  1           D   192.168.2.2     GigabitEthernet
0/0/1
        1.1.1.1/32  O_NSSA  150  101         D   192.168.2.5     GigabitEthernet
0/0/1
       10.1.2.0/24  OSPF    10   2           D   192.168.2.2     GigabitEthernet
0/0/1
OSPF routing table status : <Inactive>
         Destinations : 0        Routes : 0


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Sapte
Sapte Created Apr 15, 2020 18:11:35

hi @rcavezzale

Please be sure there is no external route advertisement in OSPF are except NSSA area,also I've tested topology for NSSA and imported static route.

If there is a 2 default route information on ABR,router will select lsa type 3 router default route instead type 7,

In order to analyze your structure and help you,could you please share your topology via GitHub or mailbox ?
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rcavezzale
rcavezzale Created Apr 15, 2020 19:08:21

There is no the LSA type 3 for default route in NSSA area.
The ABR generate default route with LSA Type 7 like Huawei documentation/output configuration

However I send you all detail on github ASAP
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chenhui
chenhui Admin Created Apr 16, 2020 02:22:05

Posted by rcavezzale at 2020-04-15 19:08 There is no the LSA type 3 for default route in NSSA area. The ABR generate default route with LSA T ...
So, you are trying to get the ABR to advertise a LSA type 3 default route into the NSSA area?
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