LSA refresh timer.

I have read that there is a 30 minutes LSA refresh timer.

So the LSA originating router has to refresh the LSA at 1800 secs..right?

R3#sh ip os da

            OSPF Router with ID (3.3.3.3) (Process ID 100)

                Router Link States (Area 1)

Link ID         ADV Router      Age         Seq#       Checksum Link count
2.2.2.2         2.2.2.2         315         0x8000002E 0x002C7A 2
3.3.3.3         3.3.3.3         388         0x80000036 0x0021F9 4
4.4.4.4         4.4.4.4         1959        0x80000026 0x00CEB1 2

I am wondering why here I am seeing a LSA age to 1959? Isn't that to be refreshed at 1800?

Comments

  • I see the same in LSA type-2 also.

     

                    Net Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum
    23.1.1.2        3.3.3.3         1124        0x80000021 0x007866
    34.1.1.2        4.4.4.4         1853        0x8000002B 0x000BB2

  • Maybe LSA pacing is the reason. The maxage is 3600, until then, the LSA is valid. 

  • I was continously capturing the LSDB. I have seen that one LSA refreshed after 1989.



                OSPF Router with ID (3.3.3.3) (Process ID 100)

                    Router Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum Link count
    2.2.2.2         2.2.2.2         1989        0x80000034 0x002080 2
    3.3.3.3         3.3.3.3         77          0x8000003D 0x001301 4
    4.4.4.4         4.4.4.4         1576        0x8000002D 0x00C0B8 2

                    Net Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum
    23.1.1.2        3.3.3.3         77          0x80000023 0x007468
    34.1.1.2        4.4.4.4         808         0x8000002D 0x0007B4

                    Summary Net Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum
    1.1.1.0         2.2.2.2         1494        0x8000001C 0x000A8A
    1.1.1.129       2.2.2.2         1742        0x80000007 0x002286
    12.1.1.0        2.2.2.2         244         0x8000001B 0x006F9C
    15.1.1.0        2.2.2.2         1494        0x8000001A 0x0054B4
    25.1.1.0        2.2.2.2         244         0x8000001E 0x00BF3C
    45.1.1.0        2.2.2.2         245         0x8000001D 0x00C621

                    Summary ASB Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum
    5.5.5.5         2.2.2.2         245         0x8000001D 0x002AD8

                    Type-5 AS External Link States

    Link ID         ADV Router      Age         Seq#       Checksum Tag
    5.5.5.0         5.5.5.5         1457        0x8000002E 0x00458A 0
    5.5.5.128       5.5.5.5         1457        0x80000018 0x006CF8 0
    R3#sh ip os da

                OSPF Router with ID (3.3.3.3) (Process ID 100)

                    Router Link States (Area 1)

    Link ID         ADV Router      Age         Seq#       Checksum Link count
    2.2.2.2         2.2.2.2         2           0x80000035 0x001E81 2
    3.3.3.3         3.3.3.3         80          0x8000003D 0x001301 4
    4.4.4.4         4.4.4.4         1579        0x8000002D 0x00C0B8 2


    I believe that it is related to the group pacing timer which is 240 sec. But still wondering it didn't refresh at 2040(1800+240). [:O]

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