Equal cost paths from separate OSPF Processes

I came across a quirk in 12.0(23) where OSPF will permit the installation of
equal cost routes (default in this case) from two separate processes &
areas. You can see in a couple of places that all interfaces encompassed by
the network statements are valid in all OSPF processes. 12.2(12a) does not
behave in the same manner. Assuming this was either a 'feature' in 12.0, or
perhaps a defect?

In this lab 0.0.0.0/0 is originated from two hops away from the access
router (two routers in the core, the distribution layer router are adjacent
to the access router).

Is there a way to toggle this behaviour in 12.2+? Comparison of the
behaviours below (same router & config, different images).

Thx
mosfet


interface Serial0.300 point-to-point
description p2p pvc to dist router 1 ospf test
bandwidth 2000
ip address 192.168.4.2 255.255.255.240
no ip redirects
no ip directed-broadcast
ip ospf authentication-key 7 12345678
ip ospf priority 0
frame-relay interface-dlci 300
!
interface Serial0.301 point-to-point
description p2p pvc to dist router 2 ospf test
bandwidth 2000
ip address 192.168.5.2 255.255.255.240
no ip redirects
ip directed-broadcast
ip ospf authentication-key 7 12345678
ip ospf priority 0
frame-relay interface-dlci 301
!
router ospf 5
log-adjacency-changes
area 192.168.4.0 authentication
redistribute connected subnets
redistribute static subnets
network 192.168.4.0 0.0.0.15 area 192.168.4.0
distribute-list permit-default in
!
router ospf 10
log-adjacency-changes
area 192.168.5.0 authentication
redistribute connected subnets
redistribute static subnets
network 192.168.5.0 0.0.0.15 area 192.168.5.0
distribute-list permit-default in
!
ip access-list standard permit-default
permit 0.0.0.0
deny any


router#sh ver
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-I-L), Version 12.0(23), RELEASE SOFTWARE (fc1)
...

router#sh ip ospf neigh

Neighbor ID Pri State Dead Time Address Interface
172.21.254.154 99 FULL/ - 00:00:30 192.168.4.1
Serial0.300
172.21.254.153 99 FULL/ - 00:00:33 192.168.5.1
Serial0.301

router#sh ip route ospf
O*E1 0.0.0.0/0 [110/76] via 192.168.4.1, 00:02:34, Serial0.300
[110/76] via 192.168.5.1, 00:02:42, Serial0.301

router#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 5", distance 110, metric 76, candidate default path
Tag 5, type extern 1
Redistributing via ospf 5
Last update from 192.168.4.1 on Serial0.300, 00:08:15 ago
Routing Descriptor Blocks:
* 192.168.4.1, from 172.21.254.156, 00:08:15 ago, via Serial0.300
Route metric is 76, traffic share count is 1
192.168.5.1, from 172.21.254.156, 00:08:24 ago, via Serial0.301
Route metric is 76, traffic share count is 1

router#sh ip ospf 5 nei de
Neighbor 172.21.254.154, interface address 192.168.4.1
In the area 192.168.4.0 via interface Serial0.300
Neighbor priority is 99, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options 66
Dead timer due in 00:00:35
Neighbor 172.21.254.153, interface address 192.168.5.1
In the area 192.168.5.0 via interface Serial0.301
Neighbor priority is 99, State is FULL, 12 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options 66
Dead timer due in 00:00:34

router#sh ip ospf 10 nei de
Neighbor 172.21.254.154, interface address 192.168.4.1
In the area 192.168.4.0 via interface Serial0.300
Neighbor priority is 99, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options 66
Dead timer due in 00:00:34
Neighbor 172.21.254.153, interface address 192.168.5.1
In the area 192.168.5.0 via interface Serial0.301
Neighbor priority is 99, State is FULL, 12 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options 66
Dead timer due in 00:00:34

router#sh ip ospf
Routing Process "ospf 10" with ID 192.168.5.2
Supports only single TOS(TOS0) routes
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
<snip>
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Area 192.168.5.0
Number of interfaces in this area is 1
Area has simple password authentication
SPF algorithm executed 5 times
<snip>

Routing Process "ospf 5" with ID 172.21.254.155
Supports only single TOS(TOS0) routes
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
<snip>
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Area 192.168.4.0
Number of interfaces in this area is 1
Area has simple password authentication
SPF algorithm executed 4 times
<snip>


router#ping ip
Target IP address: 192.168.2.5
Repeat count [5]: 2
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]: R
Number of hops [ 9 ]:
Loose, Strict, Record, Timestamp, Verbose[RV]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 2, 100-byte ICMP Echos to 192.168.2.5, timeout is 2 seconds:
Packet has IP options: Total option bytes= 39, padded length=40
Record route: <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)

Reply to request 0 (8 ms). Received packet has options
Total option bytes= 40, padded length=40
Record route:
(192.168.4.2)
(192.168.2.6)
(192.168.2.5)
(192.168.2.5)
(192.168.4.1)
(192.168.4.2) <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
End of list

Reply to request 1 (12 ms). Received packet has options
Total option bytes= 40, padded length=40
Record route:
(192.168.5.2)
(192.168.2.2)
(192.168.2.5)
(192.168.2.1)
(192.168.5.1)
(192.168.5.2) <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
End of list

Success rate is 100 percent (2/2), round-trip min/avg/max = 8/10/12 ms


--


router#sh ver | inc IOS
IOS (tm) 2500 Software (C2500-JS-L), Version 12.2(12a), RELEASE SOFTWARE
(fc1)

router#sh ip ospf neigh

Neighbor ID Pri State Dead Time Address Interface
172.21.254.153 99 FULL/ - 00:00:37 192.168.5.1
Serial0.301
172.21.254.154 99 FULL/ - 00:00:38 192.168.4.1
Serial0.300

router#sh ip route ospf
O*E1 0.0.0.0/0 [110/76] via 192.168.4.1, 00:00:10, Serial0.300

router#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 5", distance 110, metric 76, candidate default path
Tag 5, type extern 1
Last update from 192.168.4.1 on Serial0.300, 00:03:39 ago
Routing Descriptor Blocks:
* 192.168.4.1, from 172.21.254.156, 00:03:39 ago, via Serial0.300
Route metric is 76, traffic share count is 1

router#sh ip ospf 5 nei de
Neighbor 172.21.254.154, interface address 192.168.4.1
In the area 192.168.4.0 via interface Serial0.300
Neighbor priority is 99, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x42
Dead timer due in 00:00:31
Neighbor is up for 00:01:48
Index 1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec

router#sh ip ospf 10 nei de
Neighbor 172.21.254.153, interface address 192.168.5.1
In the area 192.168.5.0 via interface Serial0.301
Neighbor priority is 99, State is FULL, 6 state changes
DR is 0.0.0.0 BDR is 0.0.0.0
Options is 0x42
Dead timer due in 00:00:36
Neighbor is up for 00:01:53
Index 1/1, retransmission queue length 0, number of retransmission 0
First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
Last retransmission scan length is 0, maximum is 0
Last retransmission scan time is 0 msec, maximum is 0 msec

router#sh ip ospf
Routing Process "ospf 10" with ID 192.168.5.2
Supports only single TOS(TOS0) routes
Supports opaque LSA
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
<snip>
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Area 192.168.5.0
Number of interfaces in this area is 1
Area has simple password authentication
SPF algorithm executed 3 times
<snip>

Routing Process "ospf 5" with ID 172.21.254.155
Supports only single TOS(TOS0) routes
Supports opaque LSA
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
<snip>
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Area 192.168.4.0
Number of interfaces in this area is 1
Area has simple password authentication
SPF algorithm executed 3 times
<snip>

router#ping ip
Target IP address: 192.168.2.5
Repeat count [5]: 2
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]: R
Number of hops [ 9 ]:
Loose, Strict, Record, Timestamp, Verbose[RV]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 2, 100-byte ICMP Echos to 192.168.2.5, timeout is 2 seconds:
Packet has IP options: Total option bytes= 39, padded length=40
Record route: <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)

Reply to request 0 (12 ms). Received packet has options
Total option bytes= 40, padded length=40
Record route:
(192.168.4.2)
(192.168.2.6)
(192.168.2.5)
(192.168.2.5)
(192.168.4.1)
(192.168.4.2) <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
End of list

Reply to request 1 (12 ms). Received packet has options
Total option bytes= 40, padded length=40
Record route:
(192.168.4.2)
(192.168.2.6)
(192.168.2.5)
(192.168.2.5)
(192.168.4.1)
(192.168.4.2) <*>
(0.0.0.0)
(0.0.0.0)
(0.0.0.0)
End of list

Success rate is 100 percent (2/2), round-trip min/avg/max = 12/12/12 ms


.

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