OSPF Summarisation of Redistributed Static Routes

[ryan-barton]

Hi I have the following topology in GNS3:

Currently only concerned with R1/2/3 which are all in area 0, I have created static routes on R1 as below:

ip route 77.1.0.0 255.255.255.0 66.1.1.2
ip route 77.1.1.0 255.255.255.0 66.1.1.2
ip route 77.1.2.0 255.255.255.0 66.1.1.2
ip route 77.1.3.0 255.255.255.0 66.1.1.2

I have redistributed these into OSPF and have the below config:

router ospf 1
router-id 1.1.1.1
auto-cost reference-bandwidth 100000
area 123 nssa no-summary
summary-address 77.1.0.0 255.255.252.0
redistribute static metric-type 1 subnets
passive-interface default
no passive-interface GigabitEthernet1/0
no passive-interface Loopback0

I want to summarise the 77.1.0.0, 71.1.2.0 and 71.1.3.0 into the summary address summary-address 77.1.0.0 255.255.252.0 but still want to have a specific route to the 71.1.1.0 network, how can i do this?

[ryan-barton]

Sorry I meant R1/2/3 are all in area 123 not area 0

[MHM Cisco World]

You need two router to add NSSA area to topology then redistrubte static to ASBR of NSSA area then summary these prefix.

MHM

[ryan-barton]

Thanks MHM,

already have NSSA area configured on R3 aswell as below:

router ospf 1
router-id 3.3.3.3
auto-cost reference-bandwidth 100000
area 123 nssa no-summary
redistribute static metric-type 1 subnets
passive-interface default
no passive-interface GigabitEthernet1/0
no passive-interface GigabitEthernet2/0
no passive-interface GigabitEthernet3/0
no passive-interface Loopback0

I can also see the summary route on R3:

O N1 77.1.0.0/22 [110/121] via 192.168.13.1, 00:02:32, GigabitEthernet1/0

Just unsure how to also ensure the more specific 71.1.1.0 route is also shown

[MHM Cisco World]

Got it' 

I will check how we can get summary and only one prefix

MHM

[MHM Cisco World]

sorry I can not find solution 
you can use 
summary-add <> not-adv 
to prevent ABR of NSSA to translate some prefix but 
make summary and prevent translate that not work 

MHM

[paul driver]

Hello @MHM Cisco World 

Remove those existing summary's and add the following:

summary address 1.0.0.0 255.0.0.0
summary address 1.1.0.0 255.255.0.0

[MHM Cisco World]

Friend this not work 

When you summary to 1.0.0.0 255.0.0.0

All prefix within this range will not advertise i.e. 1.1.0.0 255.255.0.0 and 1.2.0.0 and so on

That why I answer him, he can not get both use summary abd prevent some prefix 

MHM

[paul driver]

Hello

---

@MHM Cisco World wrote:

That why I answer him, he can not get both use summary abd prevent some prefix 

---

This IS possible, you just need two summary's, one being more specific related to the "leaked" route, in your OP you have the summarys statements incorrect

[MHM Cisco World]

friend share lab to make it short for all 
as I mention again I have three 1.1.0.0 1.2.0.0 1.3.0.0 I can make ABR not translate LSA7 into LSA5 for only 1.1.0.0 that it 
I can not summary three prefix into one 1.0.0.0/8 and advertise two 1.2.0.0 and 1.3.0.0

that all 
Thanks

MHM

[paul driver]

---

@MHM Cisco World wrote:

All prefix within this range will not advertise i.e. 1.1.0.0 255.255.0.0 and 1.2.0.0 and so on

---

correct as it is a summary! -  however is you wish to "LEAK" a specific route from that summary from an ASBR you just need to add an additional summary which is more specific to the route you wish to advertise.

[MHM Cisco World]

and He ask how we can do this leak 
I answer I couldnt found solution
if you have answer him with lab 
simple lab three routers 
MHM

[paul driver]

Hello @MHM Cisco World @ryan-barton 
I have not labbed this, not access to at this time anyway, but i believe I dont need to the ASBR summary's as I explained should work ...

Based on the  OP the cfg I have previously posed also should work accordingly 

[paul driver]

Hello

R1 = ASBR
R3 = ABR of the ASBR

So if you make r3 a NSSA ( so NOT a  not-to-totally stubby area)  R3 should receive all the specific routes as well of all the other internal rtrs to area 123 whilst the all other areas just receive a summary

EDITED

R1 (ASBR 123)
router opsf 1
summary-address 77.1.0.0 255.255.252.0
summary-address 77.1.1.0 255.255.255.0
area 123 nssa

R3 (ABR for area 123)
router ospf 1
area 123 nssa no-summary
summary-address 77.1.0.0 255.255.252.0

[ryan-barton]

Hello Paul,

Thanks for your feedbcak, is there a reason the 2 routers cannot be totally NSSA in this scenario?

Kind Regards,
Ryan