OSPF Area Range - Passive Advertise (not Passive-Interface)

[ramiller]

I have been trying to figure why a summary route using the Area Range command goes into a Passive Advertise state under the OSPF process... Can anyone shed light on this..... Thanks in advance......

[Richard Burts]

Robert

It would be helpful if you could provide some details of this situation: the OSPF config, what is the topology and who are the neighbors. Do the routes exist that you are trying to summarize?

HTH

Rick

[ilya.varlashkin]

It's likely that you have situation where there are no routes in the routing table matching that range. Summarisation is the way to aggregate routes which are already in the routing table. This is done to at least partially mitigate "brain split" problem where area has several ABR and one of them got actually disconnected from the area. If summary would be advertised anyway, then traffic could be blackhole'd.

[ramiller]

The 6509-1 and 6509-2 have gigethernet between them.

6509-1 has DS3 to RR-6509

6509-2 has DS3 to SH-6509

the issue:

the DS3 link between 6509-2 and SH-6509 has been dropping.

When this happens, the summary route 172.21.0.0 on 6509-1 goes into a "passive advertised" state and no longer advertises to RR-6509.

To test, I verified all routing was correct and all links up. All Ospf neighbors are in proper state

I manually shutdown the interface on 6509-2 to SH-6509. Again, the summary route on 6509-1 went into a "passive advertised" state. I manually brought the summary route active on 6509-1 by re-inputting the Area Range command. Then I brought the DS3 interface on 6509-2 back up. When I did this, the summary route on 6509-1 went into a "passive advertise" again

Ospf configs and abbreviated ip table is included:

6509-1#sh run | beg router ospf

router ospf 1

router-id 172.21..1.2

ispf

log-adjacency-changes

auto-cost reference-bandwidth 1000

area 172 range 172.21.0.0 255.255.0.0

network 172.20.40.220 0.0.0.3 area 0

network 172.21.0.0 0.0.255.255 area 172

6509-1#sh ip route connected

172.21.0.0/16 is variably subnetted, 440 subnets, 13 masks

C 172.21.102.0/24 is directly connected, Vlan102

C 172.21.100.0/24 is directly connected, Vlan100

C 172.21.110.0/24 is directly connected, Vlan110

C 172.21.104.0/22 is directly connected, Vlan104

C 172.21.118.0/24 is directly connected, Vlan118

6509-1#sh ip route 172.21.0.0

Routing entry for 172.21.0.0/16

Known via "ospf 1", distance 110, metric 0, type intra area

Routing Descriptor Blocks:

* directly connected, via Null0

Route metric is 0, traffic share count is 1

6509-1#sh ip ospf

Routing Process "ospf 1" with ID 172.21.1.2

(Area 0 - text removed)

Area 172

Number of interfaces in this area is 23

Area has no authentication

SPF algorithm last executed 03:53:45.684 ago

SPF algorithm executed 3 times

Area ranges are

172.21.0.0/16 Active(1) Advertise

6509-2#sh run | beg router ospf

router ospf 1

router-id 172.21.1.3

ispf

log-adjacency-changes

auto-cost reference-bandwidth 1000

area 172 range 172.21.0.0 255.255.0.0

network 172.20.40.224 0.0.0.3 area 0

network 172.21.0.0 0.0.255.255 area 172

6509-2#sh ip route connected

172.21.0.0/16 is variably subnetted, 440 subnets, 13 masks

C 172.21.102.0/24 is directly connected, Vlan102

C 172.21.100.0/24 is directly connected, Vlan100

C 172.21.110.0/24 is directly connected, Vlan110

C 172.21.104.0/22 is directly connected, Vlan104

C 172.21.118.0/24 is directly connected, Vlan118

6509-2#sh ip route 172.21.0.0

Routing entry for 172.21.0.0/16

Known via "ospf 1", distance 110, metric 0, type intra area

Routing Descriptor Blocks:

* directly connected, via Null0

Route metric is 0, traffic share count is 1

6509-2#sh ip ospf

Routing Process "ospf 1" with ID 172.21.1.3

(Area 0 text removed)

Area 172

Number of interfaces in this area is 23

Area has no authentication

SPF algorithm last executed 03:55:01.672 ago

SPF algorithm executed 5 times

Area ranges are

172.21.0.0/16 Active(1) Advertise

[Richard Burts]

Robert

The additional detail that you have provided is helpful but is not quite enough. In particular we need to know about the connection between 6509-1 and 6509-2. Given that both routers seem to share 172.21.100.0, 172.21.102.0, 172.21.104.0, 172.21.110.0, and 172.21.118.0 in area 172 do we assume that they are connected on each of these? Where is area 0 on these routers? Similarly it would be helpful to know about the connection to RR-6509 and SH-6509. What areas are they in?

HTH

Rick

[ramiller]

6509-1 <> RR-6509 DS3 Area 0 172.20.40.220/30

6509-2 <> SH-6509 DS3 Area 0 172.20.40.224/30

6509-1 <> 6509-2 (GigE L2 Trunk / L3 HSRP for each Vlan) Area 172 172.21.0.0/16

[sivam siva]

Hello 

If there is no subnet (type 1 or type 2 LSA in LSDB ) exist in that summarized range, then the router wont advertise the summarized route ( as type 3 LSA ) , so the status of that configured summary route will get into " Passive Advertise " state.