Hello
I would like to share with you a problem concerning OSPF NSSA :
I have always figured myself that in a NSSA area with 2 routers, only one is supposed to perform translation.
A NSSA translator is supposed to be elected, and only this router will perform LSA7 to LSA5 translations.
I have an example where this rule seems to be broken, 2 cisco 7600 routers are connected to a NSSA area(33)
an both are performing translations.
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WAN_7604_1#sh ip ospf
Routing Process "ospf 100" with ID 10.255.255.101
Start time: 1d00h, Time elapsed: 4d20h
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
Event-log enabled, Maximum number of events: 1000, Mode: cyclic
It is an area border and autonomous system boundary router
Redistributing External Routes from,
Router is not originating router-LSAs with maximum metric
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 2. Checksum Sum 0x00F729
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
Number of areas transit capable is 0
External flood list length 0
IETF NSF helper support enabled
Cisco NSF helper support enabled
Reference bandwidth unit is 100 mbps
Area BACKBONE(0)
Number of interfaces in this area is 11
Area has no authentication
SPF algorithm last executed 00:48:36.856 ago
SPF algorithm executed 10 times
Area ranges are
Number of LSA 44. Checksum Sum 0x1CA836
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 33
Number of interfaces in this area is 1
It is a NSSA area
Perform type-7/type-5 LSA translation
Area has no authentication
SPF algorithm last executed 20:35:03.876 ago
SPF algorithm executed 9 times
Area ranges are
192.168.0.0/16 Passive Advertise
Number of LSA 23. Checksum Sum 0x0CBAE8
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
WAN_7604_1#sh ip ospf database nssa-external
OSPF Router with ID (10.255.255.101) (Process ID 100)
Type-7 AS External Link States (Area 33)
Routing Bit Set on this LSA in topology Base with MTID 0
LS age: 156
Options: (No TOS-capability, Type 7/5 translation, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 172.20.4.242
LS Seq Number: 80000026
Checksum: 0x79B3
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.33.1
External Route Tag: 65333
WAN_7604_1#sh ip ospf database external
OSPF Router with ID (10.255.255.101) (Process ID 100)
Type-5 AS External Link States
LS age: 149
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 10.255.255.101
LS Seq Number: 80000026
Checksum: 0xD3AB
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.33.1
External Route Tag: 65333
LS age: 1113
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 10.255.255.102
LS Seq Number: 80000002
Checksum: 0x237E
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.34.1
External Route Tag: 65333
WAN_7604_1#
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WAN_7604_2#sh ip ospf
Routing Process "ospf 100" with ID 10.255.255.102
Start time: 1d20h, Time elapsed: 01:43:19.924
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
Event-log enabled, Maximum number of events: 1000, Mode: cyclic
It is an area border and autonomous system boundary router
Redistributing External Routes from,
Router is not originating router-LSAs with maximum metric
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 2. Checksum Sum 0x02A67B
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
Number of areas transit capable is 0
External flood list length 0
IETF NSF helper support enabled
Cisco NSF helper support enabled
Reference bandwidth unit is 100 mbps
Area BACKBONE(0)
Number of interfaces in this area is 13
Area has no authentication
SPF algorithm last executed 00:49:20.432 ago
SPF algorithm executed 3 times
Area ranges are
Number of LSA 44. Checksum Sum 0x280C92
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 33
Number of interfaces in this area is 1
It is a NSSA area
Perform type-7/type-5 LSA translation
Area has no authentication
SPF algorithm last executed 00:51:19.104 ago
SPF algorithm executed 2 times
Area ranges are
Number of LSA 23. Checksum Sum 0x0E4655
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
WAN_7604_2#sh ip ospf database nssa-external
OSPF Router with ID (10.255.255.102) (Process ID 100)
Type-7 AS External Link States (Area 33)
Routing Bit Set on this LSA in topology Base with MTID 0
LS age: 1505
Options: (No TOS-capability, Type 7/5 translation, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 172.20.4.243
LS Seq Number: 80000004
Checksum: 0xC488
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.34.1
External Route Tag: 65333
WAN_7604_2#sh ip os
WAN_7604_2#sh ip ospf
WAN_7604_2#sh ip ospf d
WAN_7604_2#sh ip ospf database ex
WAN_7604_2#sh ip ospf database external
OSPF Router with ID (10.255.255.102) (Process ID 100)
Type-5 AS External Link States
LS age: 196
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 10.255.255.101
LS Seq Number: 80000026
Checksum: 0xD3AB
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.33.1
External Route Tag: 65333
LS age: 1158
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 217.0.1.0 (External Network Number )
Advertising Router: 10.255.255.102
LS Seq Number: 80000002
Checksum: 0x237E
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 100
Forward Address: 10.0.34.1
External Route Tag: 65333
WAN_7604_2#
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Thanks to enlight me, I am doubting of my IOS version
Regards