LAB: Flooding Reduction

On Area 3 configure routers switches to not participate in the periodic paranoid update LSA flooding.


When the Link State Age reaches MaxAge - the router must attempt to flush the LSA.. by reflooding the MaxAge LSA just as if it was a newly originated LSA.

default maxage value = 3600 seconds or 30 minutes.  LSA will be reflooded every 30 minutes regardless if the topology is stable.

interface command:

ip ospf flood-reduction

this will set the DNA (DoNotAge) bit in the LSA, removing the requirement for the periodic refresh.

verification before applying the command;

Rack1SW4#show ip ospf database

            OSPF Router with ID (223.255.255.255) (Process ID 1)

                Router Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum Link count
150.1.5.5       150.1.5.5       1198        0x80000002 0x00A203 3
150.1.8.8       150.1.8.8       1190        0x80000005 0x007446 4
223.255.255.255 223.255.255.255 1189        0x80000003 0x0046E7 3

                Net Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
155.1.58.5      150.1.5.5       1198        0x80000001 0x00482B
155.1.108.10    223.255.255.255 1190        0x80000001 0x003D82

                Summary Net Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
150.1.1.0       150.1.5.5       1575        0x80000001 0x00211A
150.1.2.0       150.1.5.5       1575        0x80000001 0x00E1EC
150.1.3.0       150.1.5.5       1575        0x80000001 0x00D6F6
150.1.4.0       150.1.5.5       1430        0x80000003 0x001EA7
150.1.6.0       150.1.5.5       1193        0x80000001 0x00CEC9
150.1.7.0       150.1.5.5       1239        0x80000001 0x006C30
150.1.9.0       150.1.5.5       1149        0x80000001 0x0083F8
155.1.0.1       150.1.5.5       1576        0x80000001 0x00D660
155.1.0.2       150.1.5.5       1576        0x80000001 0x009832
155.1.0.3       150.1.5.5       1576        0x80000001 0x008E3B
155.1.0.4       150.1.5.5       1431        0x80000003 0x00D6EA
155.1.0.5       150.1.5.5       1636        0x80000001 0x00CF2A
155.1.7.0       150.1.5.5       1194        0x80000001 0x004E2C
155.1.9.0       150.1.5.5       1149        0x80000001 0x0065F4
155.1.13.0      150.1.5.5       1577        0x80000001 0x00C6C6
155.1.23.0      150.1.5.5       1577        0x80000001 0x00B8FB
155.1.37.0      150.1.5.5       1577        0x80000001 0x00D5A4
155.1.45.0      150.1.5.5       1701        0x80000001 0x001288
155.1.67.0      150.1.5.5       1195        0x80000001 0x00B786
155.1.79.0      150.1.5.5       1196        0x80000001 0x0033FE
155.1.146.0     150.1.5.5       1432        0x80000003 0x007590
192.10.1.0      150.1.5.5       1577        0x80000001 0x00145C

                Summary ASB Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
192.10.1.254    150.1.5.5       1243        0x80000001 0x001060
         
                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
51.51.51.51     192.10.1.254    1690        0x80000001 0x009C6C 0

Note:  for the summaryLSA links after applying the command you need to clear the ospf process to reflect the DNA bit the the show ip ospf database command output.

after applying the command, you will noticed the (DNA) keyword in each LSA type entry.

Rack1SW4#show ip ospf database  

            OSPF Router with ID (223.255.255.255) (Process ID 1)

                Router Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum Link count
150.1.5.5       150.1.5.5       2     (DNA) 0x80000005 0x009C06 3
150.1.8.8       150.1.8.8       212   (DNA) 0x80000008 0x004277 4
223.255.255.255 223.255.255.255 39          0x80000005 0x002EFF 3

                Net Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
155.1.58.5      150.1.5.5       2     (DNA) 0x80000001 0x00482B
155.1.108.8     150.1.8.8       212   (DNA) 0x80000001 0x0055A4

                Summary Net Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
150.1.1.0       150.1.5.5       1906  (DNA) 0x80000001 0x00211A
150.1.2.0       150.1.5.5       1906  (DNA) 0x80000001 0x00E1EC
150.1.3.0       150.1.5.5       1906  (DNA) 0x80000001 0x00D6F6
150.1.4.0       150.1.5.5       1761  (DNA) 0x80000003 0x001EA7
150.1.6.0       150.1.5.5       1523  (DNA) 0x80000001 0x00CEC9
150.1.7.0       150.1.5.5       1569  (DNA) 0x80000001 0x006C30
150.1.9.0       150.1.5.5       1478  (DNA) 0x80000001 0x0083F8
155.1.0.1       150.1.5.5       1906  (DNA) 0x80000001 0x00D660
155.1.0.2       150.1.5.5       1906  (DNA) 0x80000001 0x009832
155.1.0.3       150.1.5.5       1906  (DNA) 0x80000001 0x008E3B
155.1.0.4       150.1.5.5       1761  (DNA) 0x80000003 0x00D6EA
155.1.0.5       150.1.5.5       1966  (DNA) 0x80000001 0x00CF2A
155.1.7.0       150.1.5.5       1524  (DNA) 0x80000001 0x004E2C
155.1.9.0       150.1.5.5       1478  (DNA) 0x80000001 0x0065F4
155.1.13.0      150.1.5.5       1906  (DNA) 0x80000001 0x00C6C6
155.1.23.0      150.1.5.5       1906  (DNA) 0x80000001 0x00B8FB
155.1.37.0      150.1.5.5       1906  (DNA) 0x80000001 0x00D5A4
155.1.45.0      150.1.5.5       2030  (DNA) 0x80000001 0x001288
155.1.67.0      150.1.5.5       1524  (DNA) 0x80000001 0x00B786
155.1.79.0      150.1.5.5       1524  (DNA) 0x80000001 0x0033FE
155.1.146.0     150.1.5.5       1761  (DNA) 0x80000003 0x007590
192.10.1.0      150.1.5.5       1906  (DNA) 0x80000001 0x00145C

                Summary ASB Link States (Area 3)

Link ID         ADV Router      Age         Seq#       Checksum
192.10.1.254    150.1.5.5       1572  (DNA) 0x80000001 0x001060
         
                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
51.51.51.51     192.10.1.254    2019  (DNA) 0x80000001 0x009C6C 0