LSA for filtering Type 3 in the OSPF environment-test
Test-filter LSA of Type 3 that enters area 0 on R1
R1 (config-router) # area 0 filter-list prefix lsa3in in
View the R1 Database
- R1#show ip ospf database
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- OSPF Router with ID (1.1.1.1) (Process ID 1)
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- Router Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 1348 0x80000004 0x0010BC 1
- 2.2.2.2 2.2.2.2 1348 0x80000002 0x00D5EF 1
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- Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 10.1.1.2 2.2.2.2 1349 0x80000001 0x002CEB
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- Summary Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.4.0 2.2.2.2 1680 0x80000001 0x00794D
- 192.168.5.0 2.2.2.2 1680 0x80000001 0x006E57
- 192.168.6.0 2.2.2.2 1680 0x80000001 0x006361
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- Router Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 1489 0x80000004 0x00CFF1 3
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- Summary Net Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.4.0 1.1.1.1 1335 0x80000001 0x001A70
It is found that there are only three LSA entries in Type 3 of Region 0, because only one entry of 192.168.4.0/24 is allowed in the prefix list, so three entries of Region 0 are entered from R1, 192.168.1.0/24, 192.168.2.0/24, and 192.168.3.0/24 cannot enter area 0.
Test-filter LSA of Type 3 advertised from Area 1 on R1
In R1, the LSA of Type 3 advertised from Area 1 is filtered. Only 192.168.1.0/24 is allowed.
- R1(config)#ip prefix-list lsa3out permit 192.168.1.0/24
- R1(config-router)#area 1 filter-list prefix lsa3out out
View the R1 Database
- R1#show ip ospf database
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- OSPF Router with ID (1.1.1.1) (Process ID 1)
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- Router Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 27 0x80000005 0x000EBD 1
- 2.2.2.2 2.2.2.2 1902 0x80000002 0x00D5EF 1
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- Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 10.1.1.2 2.2.2.2 1903 0x80000001 0x002CEB
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- Summary Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.4.0 2.2.2.2 365 0x80000002 0x00774E
- 192.168.5.0 2.2.2.2 365 0x80000002 0x006C58
- 192.168.6.0 2.2.2.2 365 0x80000002 0x006162
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- Router Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 27 0x80000005 0x00CDF2 3
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- Summary Net Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.4.0 1.1.1.1 30 0x80000002 0x001871
We found that there are only three items in Area 0 because only 192.168.4.0/24 is allowed in the LSA filter of area 0 just made on R1, in this way, even if 192.168.1.0/24 is allowed in the outbound stack of Area 1, it still cannot enter area 0. Therefore, you must allow 192.168.1.0/24 in the prefix list.
R1 (config) # ip prefix-list lsa3in permit 192.168.1.0/24
View the OSPF database of R1
- R1#show ip ospf database
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- OSPF Router with ID (1.1.1.1) (Process ID 1)
-
- Router Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 27 0x80000005 0x000EBD 1
- 2.2.2.2 2.2.2.2 1902 0x80000002 0x00D5EF 1
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- Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 10.1.1.2 2.2.2.2 1903 0x80000001 0x002CEB
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- Summary Net Link States (Area 0)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.1.0 1.1.1.1 4 0x80000001 0x00B815
- 192.168.4.0 2.2.2.2 365 0x80000002 0x00774E
- 192.168.5.0 2.2.2.2 365 0x80000002 0x006C58
- 192.168.6.0 2.2.2.2 365 0x80000002 0x006162
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- Router Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum Link count
- 1.1.1.1 1.1.1.1 27 0x80000005 0x00CDF2 3
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- Summary Net Link States (Area 2)
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- Link ID ADV Router Age Seq# Checksum
- 192.168.4.0 1.1.1.1 30 0x80000002 0x001871
The LSA of Type 3 of area 0 has an additional IP Address 192.168.1.0/24.
View route table on R2
R2 # show ip route ospf
O ia 192.168.1.0/24 [110/65] via 10.1.1.1, 00:05:08, Serial0
There is only one CIDR route for 192.168.1.0/24.
LSA of Type 3 in the OSPF environment-Summary
The LSA function provided by OSPF in the ABR filtering Type 3 allows you to filter a specific area in the in or out direction on the ABR. That is, LSA of Type 3 that is allowed to enter or exit the region.
Filtering LSA 1 of Type 3 on the ABR in OSPF environment)
Filtering LSA 2 of Type 3 on the ABR in OSPF environment)
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