| SNA pr subnetwork point of attachment | |
| Packet or PDUs Protocol Data Unit | Link |
Type 1: IS-IS hello (IIH) PDUs | Broadcast to discover the identity of neighboring IS-IS systems and to determine whether the neighbors are Level 1 or Level 2 intermediate systems
|
Level 1: 01:80:C2:00:00:14 Level 2: 01:80:C2:00:00:15 | |
| Link-state PDUs | Contain information about the state of adjacencies to neighboring IS-IS systems. on PtP links ack by CSNPs |
| Complete sequence number PDUs (CSNPs) | Contain a complete list of all link-state PDUs in the IS-IS database. |
| Partial sequence number PDUs (PSNPs) | Sent multicast by a receiver when it detects that it is missing a link-state PDU (when its link-state PDU database is out of date) |
| DIS Election on Broadcast & multi-access | ptp the priority = 0 |
router with the higher priority Default priority: 64 [ 0 to 127 ] Priority = 0 >> ineligible | |
| Highest priority | |
| priority tie >>> highest SNAP or Mac@ | |
| No backup DIS in IS-IS | |
| pseudo-node ( Bcst Network = router ) | on Broadcast & multi-access |
| all router adv a single link ( not all the adj ) to the pseudo-node | |
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