R3 and R4 share the same Ethernet segment 172.12.34.0 via their fastethernet0/1 interfaces
Router IDs:
R3 = 3.3.3.3
R4 = 4.4.4.4
R4 has the following LSAs from R3:
R4# show ip ospf database adv-router 3.3.3.3
OSPF Router with ID (4.4.4.4) (Process ID 1)
Router Link States (Area 345)
Link ID ADV Router Age Seq# Checksum Link count
3.3.3.3 3.3.3.3 7 0x80000012 0x00C568 2
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
172.12.123.0 3.3.3.3 550 0x8000000C 0x00D381 0
On R3 we enter the following command:
R3(config)#int f0/1
R3(config-if)#ip ospf database-filter all out
R3(config-if)#
*Mar 1 04:41:41.162: %OSPF-5-ADJCHG: Process 1, Nbr 4.4.4.4 on FastEthernet0/1
from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 04:41:41.382: %OSPF-5-ADJCHG: Process 1, Nbr 4.4.4.4 on FastEthernet0/1
from LOADING to FULL, Loading Done
Notice the adjacency bounced. However, R4 still has LSAs from R3 in it's database (they haven't been aged):
R4# show ip ospf database adv-router 3.3.3.3
OSPF Router with ID (4.4.4.4) (Process ID 1)
Router Link States (Area 345)
Link ID ADV Router Age Seq# Checksum Link count
3.3.3.3 3.3.3.3 59 0x80000012 0x00C568 2
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
172.12.123.0 3.3.3.3 603 0x8000000C 0x00D381 0
We must clear the ospf process on R4:
R4#clear ip ospf process
Reset ALL OSPF processes? [no]: yes
Mar 1 04:52:47.442: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on FastEthernet0/1 f
rom FULL to DOWN, Neighbor Down: Interface down or detached
Mar 1 04:52:47.806: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on FastEthernet0/1 f
rom LOADING to FULL, Loading Done
Now the type 1 router LSA from R3 is gone from R4's LSDB:
R4# show ip ospf database adv-router 3.3.3.3
OSPF Router with ID (4.4.4.4) (Process ID 1)
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
172.12.123.0 3.3.3.3 674 0x8000000C 0x00D381 0
But the type 5 LSA still exists...Why? Don't know yet, stay tuned...
Saturday, June 14, 2008
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I know you may be already knowing all this now as you already own CCIE # .. But I think this will be a good ref for me.. So I don't want to miss the chance to add my findings and your input is also welcome...
ReplyDelete1st = You were needed to clear Adj before 3.0.0.0 disappeared from R4's routing table, As Neighbor Rel'ship was still there when we configured LSA Filtering.. and No change in network 3.0.0.0 so no LSA Flooding.. but this change just reset the LSA Age to zero
In short, R4 will not remove this 3.0.0.0 until 30 min - Default LSA Refresh Timer.
But I am unable to reproduce symptom you had faced - leaving type-5 lsa in ospf database on R4... Strange.
Thanks for the post! This was such a long time ago I did this, I never did revisit the scenario. I wonder if there something wrong in the way I labbed this. Anyways, I always recommend to lab for yourself and see :)
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