[c-nsp] OSPF summary LSA - expected behavior

[Chris Cox]

Hello,

Just wondering if anyone could confirm what the expected behavior is when a
router running ospf receives a new summary-lsa with regards to external
routes ?

I have the following in a lab at the moment and find with some versions of
IOS (currently 12.4(1a) but also see this with 12.3(11)T3) that whenever
ABR2 or NSSA-2 receive a sumary-lsa as a result of a route being originated
by NSSA3 then all external routes on ABR2 and and NSSA-2 are recalculated.

NSSA-3 ------ ABR1--<area0>--ABR2-----NSSA-2

Yet if ABR2 and NSSA-2 are running various other versions of IOS including
12.3-8.T8, 12.2(6), 12.1(27a) then this doesn't happen.

I've placed the router config's and some debug output below.

Any idea what's going on here or am I missing something obvious ?

Many Thanks,

Chris Cox


! NSSA 2 - 7204VXR
interface Loopback1
 ip address 10.10.10.10 255.255.255.255
!
interface FastEthernet2/1
 ip address 10.0.0.1 255.255.255.252
 duplex half
!
router ospf 1
 log-adjacency-changes
 area 0.0.0.2 nssa
 redistribute connected subnets
 redistribute static subnets
 network 10.0.0.0 0.0.0.3 area 0.0.0.2

! ABR 2 - 7204VXR
interface Serial1/0
 ip address 10.0.0.5 255.255.255.252
 encapsulation ppp
 serial restart-delay 0
 no fair-queue
!
interface FastEthernet2/0
 ip address 10.0.0.2 255.255.255.252
 duplex half
!
router ospf 1
 log-adjacency-changes
 area 0.0.0.2 nssa
 network 10.0.0.0 0.0.0.3 area 0.0.0.2
 network 10.0.0.4 0.0.0.3 area 0.0.0.0

! ABR1 - 2621
interface FastEthernet0/0
 ip address 10.0.0.9 255.255.255.252
 duplex auto
 speed auto
!
interface Serial0/0
 ip address 10.0.0.6 255.255.255.252
 encapsulation ppp
 clockrate 2000000
 no fair-queue
!
router ospf 1
 log-adjacency-changes
 area 0.0.0.3 nssa
 network 10.0.0.4 0.0.0.3 area 0.0.0.0
 network 10.0.0.8 0.0.0.3 area 0.0.0.3

! NSSA3 - 2610
interface Loopback15
! bouncing this interface causes all external routes
! on ABR2 and NSSA3 to recaculate with certain
! versions of IOS
 ip address 1.1.1.1 255.255.255.255
!
interface Ethernet0/0
 ip address 10.0.0.10 255.255.255.252
!
router ospf 1
 redistribute static subnets
 network 1.1.1.1 0.0.0.0 area 0.0.0.3
 network 10.0.0.8 0.0.0.3 area 0.0.0.3
 area 0.0.0.3 nssa

The output from 'show ip ospf stat' and 'debug ip ospf monitor' on NSSA2
when this happens is as follows.......

OSPF process ID 1
------------------------------------------

  Area 0.0.0.2: SPF algorithm executed 10 times

  Summary OSPF SPF statistic

  SPF calculation time
Delta T   Intra D-Intra Summ    D-Summ  Ext     D-Ext   Total   Reason
19:52:28   0    0       0       0       0       0       0       R,
19:51:43   0    0       0       0       0       0       0       R, N,
19:51:33   0    0       0       0       0       0       4       R, SN, X
19:09:22   0    0       0       0       0       0       0       X
00:47:55   0    0       0       0       0       0       0       X
00:46:06   0    0       0       0       0       0       0       X
00:41:04   0    0       0       0       0       0       0       X
00:39:51   0    0       0       0       0       0       0       X
00:38:54   0    0       0       0       0       0       0       X
00:00:35   0    0       0       0       0       0       0       X

      Change in LS ID 1.1.1.1, LSA type X, spf-type Prefix Recalculation
*Jun 15 10:04:54.610: OSPF: reset throttling to 5000ms
*Jun 15 10:04:54.610: OSPF: schedule SPF: spf_time 21:32:15.428
wait_interval 5000ms
*Jun 15 10:04:59.610: OSPF: Begin SPF at 77540.428ms, process time 100ms
*Jun 15 10:04:59.610:       spf_time 21:32:15.428, wait_interval 5000ms
*Jun 15 10:04:59.610: OSPF: wait_interval 10000ms next wait_interval 10000ms
*Jun 15 10:04:59.610: OSPF: End SPF at 77540.428ms, Total elapsed time 0ms
*Jun 15 10:04:59.610:       Schedule time 21:32:20.428, Next wait_interval
10000ms
*Jun 15 10:04:59.610:       Intra: 0ms, Inter: 0ms, External: 0ms
*Jun 15 10:04:59.610:       R: 0, N: 0, Stubs: 0
*Jun 15 10:04:59.610:       SN: 0, SA: 0, X5: 0, X7: 0
*Jun 15 10:04:59.610:       SPF suspends: 0 intra, 0 total