9 good questions and answers about "IS-IS Operation over Broadcast Links"

What are the selection criteria for a DIS?
-Router with highest interface priority
-In case of tie; Router with highest SNPA (Sub network Point of Attachment)
-In case SNPAs are not comparable (frame relay/ATM) Router with highest system ID.
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What is the command to configure the DIS priority?
What are the priority values ?
What priority value is better?
router isis WORD

priority
priority [level] 0 127
higher is better
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What is the DIS responsible for?
-Helping routers on a broadcast segment to synchronize
-Representing the broadcast segment in the link-state database as a standalone object; the Pseudonode
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What are the possibilities when a router recieves a CSNP packet from a DIS? 3
-Router has LSP with same LSPID in its linkstate database==> no action performed
-Router does not have an LSP with the indicated LSPID in its link-state database or sequence number on DIS is higher
-Router has an LSP with the same LSPID in its link-state database but its sequence number on the DIS is lower or the DIS not advertise this LSPID.
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What is the action when a Router does not have an LSP with the indicated LSPID in its link-state database or sequence number on DIS is higher?
The router needs to download the LSP from the DIS by creating a PSNP requesting the LSP in question and forwarding it onto the segment. The DIS will recieve the PSNP and flood the requested LSP.
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What is the action when the PSNP or LSP get lost during transmission?
It wil be send again.
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Who is responsible to orginate and flood the Pseudonode LSP on a broadcast network?
DIS
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What will happen when the DIS fails? 4
-Another router will be elected.
-No additional adjacency necessary ( all routers are fully adjacent)
-Pseudonode LSP will be replaced by the new elected DIS
-Routers will update their LSPs to point toward the new Pseudonode LSP
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What is the difference between a network LSP or a router LSP?
-Network LSP or Pseudonode LSP, the System ID is the ID of the DIS and the Pseudonode ID is set to the LOCAL Circuit ID of the DIS's interface network.

-Router LSP , the System-ID carries the ID of the router and the Pseudonode is set to 0
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