When 4 x 0 != 0

As we all know, OSPF area ID is a 32-bit quantity that can be written as a decimal number or as a dotted decimal (although I never really understood the need for dotted decimal support). You would expect both representations to behave identically (after all, it’s a 32 bit number we’re talking about) and most often they do. However, Murali reported an interesting bug: some show commands do not understand that 4 times zero still equals zero.

If you execute the show ip ospf process 0 database self-originate command, you’ll get the list of LSAs the router originates into the backbone area. The show ip ospf process 0.0.0.0 database self-originate command does not display any LSAs (tested on 12.2(33)SRC4).

C2#show ip ospf 1 0 database self-originate 

            OSPF Router with ID (10.0.1.7) (Process ID 1)

Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
10.0.1.7        10.0.1.7        203         0x80000003 0x009303 4

Summary Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
10.0.1.5        10.0.1.7        204         0x80000001 0x003EA9
10.0.1.6        10.0.1.7        170         0x80000002 0x009645
10.0.7.8        10.0.1.7        204         0x80000001 0x00B7F8
10.0.7.16       10.0.1.7        204         0x80000001 0x007169
10.0.7.32       10.0.1.7        204         0x80000001 0x00D0F9
10.2.1.0        10.0.1.7        204         0x80000001 0x00B22F

Type-10 Opaque Link Area Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Opaque ID
1.0.0.0         10.0.1.7        215         0x80000001 0x005EAF 0       
1.0.0.3         10.0.1.7        35          0x80000002 0x00765B 3       
1.0.0.4         10.0.1.7        212         0x80000001 0x00B54A 4       
C2#show ip ospf 1 0.0.0.0 database self-originate

            OSPF Router with ID (10.0.1.7) (Process ID 1)

4 comments:

  1. Doesnt work on a 3745 and 12.4(15)T5 either :-D

    ReplyDelete
  2. Same behaviour on 12.4(22)T1 (1841) and 12.2(50)SE1 (3550)... :)

    ReplyDelete
  3. Piotr Wojciechowski24 July, 2009 18:31

    Still exist in 12.2(33)SXI2 Funny bug :)

    ReplyDelete

You don't have to log in to post a comment, but please do provide your real name/URL. Anonymous comments might get deleted.

Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.