Thursday, March 09, 2006

 

IS-IS DIS identification. (Question #32)

Given the following output from a show isis database command on a Cisco router, can you identify
  1. the Designated Intermediate Systems (DIS) in the network
  2. the hostname of the router where this command was issued


IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R2.00-00 * 0x0000008E 0xE8BB 819 1/0/0
R3.00-00 0x0000007C 0x710E 704 0/0/0
R4.00-00 0x00000079 0x3FD3 691 0/0/0
R5.00-00 0x00000076 0x0D99 879 0/0/0
R5.01-00 0x00000080 0xA481 644 0/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R1.00-00 0x00000080 0x4DED 971 0/0/0
R2.00-00 * 0x0000007F 0xBCA2 732 0/0/0
R6.00-00 0x0000005A 0xFE20 838 0/0/0
R6.01-00 0x00000057 0xA2B2 717 0/0/0
R8.00-00 0x0000005A 0x6AE7 1048 0/0/0


Comments:
Under the LSPID column... the second from right byte (3-4th character) is the pseudonode ID... It is none zero for the DIS.

So
Level-1 has R5 as the DIS.
Level-2 has R6 as the DIS.

The * indicates the router that the command was run on. The Router hostname is also taken from the LSPID and in this case is.. R2...
 
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