Integrated IS - IS
1: What is an intermediate system?
** An Intermediate System is the ISO term for a router.
2: What is a network protocol data unit?
** A Network Protocol Data Unit is the ISO term for a packet.
3: What is the difference between an L1, an L2, and an L1/L2 router?
** An L1 router has no direct connections to another area. An L2 router only routes inter-area traffic. An L1/L2 router routes both inter-area and intra-area traffic and acts as an inter-area gateway for L1 routers.
4: Explain the basic difference between an IS-IS area and an OSPF area.
** The borders of IS-IS areas are between routers, on links. The borders of OSPF areas are defined by the routers themselves.
5: What is a network entity title (NET)?
** The Network Entity Title is an address by which a router identifies both itself and the area in which it resides.
6: To what value must the NSAP Selector be set in a NET?
** The NSAP Selector should be set to 0x00 in a NET.
7: What is the purpose of a System ID?
** The System ID uniquely identifies a router within an IS-IS domain.
8: How does a router determine what area it is in?
** The portion of the NET preceding the last seven octets is the area address.
9: Does IS-IS elect a Backup Designated Router on a broadcast subnetwork?
** IS-IS does not elect a BDR.
10: What is the purpose of the Pseudonode ID?
** The Pseudonode ID is the last octet of a LAN ID. Its purpose is to distinguish LAN IDs which are originated by a single router which is the DR on multiple LANs.
11: What is the maximum age (MaxAge) of an IS-IS LSP?
** The MaxAge of an IS-IS LSP is 1200 seconds (20 minutes).
12: What is the basic difference between the way OSPF ages its LSAs and the way IS-IS ages its LSPs?
** OSPF increments the age up to MaxAge; IS-IS decrements the age down to 0. A new OSPF LSA has an age of 0, whereas a new IS-IS LSP has an age of MaxAge.
13: How often does an IS-IS router refresh its LSPs?
** The refresh rate of an IS-IS router is 900 seconds (15 minutes).
14: What is a Complete Sequence Number Packet (CSNP)? How is it used?
** A Complete Sequence Number Packet contains a full listing of all LSPs in a database. A CSNP is periodically sent by the Designated Router on a broadcast network to maintain database synchronization.
15: What is a Partial Sequence Number Packet (PSNP)? How is it used?
** A Partial Sequence Number Packet contains a listing of one or more LSPs. It has two uses: On point-to-point networks, it is used to acknowledge the receipt of LSPs. On broadcast networks, it is used to request LSPs.
** An Intermediate System is the ISO term for a router.
2: What is a network protocol data unit?
** A Network Protocol Data Unit is the ISO term for a packet.
3: What is the difference between an L1, an L2, and an L1/L2 router?
** An L1 router has no direct connections to another area. An L2 router only routes inter-area traffic. An L1/L2 router routes both inter-area and intra-area traffic and acts as an inter-area gateway for L1 routers.
4: Explain the basic difference between an IS-IS area and an OSPF area.
** The borders of IS-IS areas are between routers, on links. The borders of OSPF areas are defined by the routers themselves.
5: What is a network entity title (NET)?
** The Network Entity Title is an address by which a router identifies both itself and the area in which it resides.
6: To what value must the NSAP Selector be set in a NET?
** The NSAP Selector should be set to 0x00 in a NET.
7: What is the purpose of a System ID?
** The System ID uniquely identifies a router within an IS-IS domain.
8: How does a router determine what area it is in?
** The portion of the NET preceding the last seven octets is the area address.
9: Does IS-IS elect a Backup Designated Router on a broadcast subnetwork?
** IS-IS does not elect a BDR.
10: What is the purpose of the Pseudonode ID?
** The Pseudonode ID is the last octet of a LAN ID. Its purpose is to distinguish LAN IDs which are originated by a single router which is the DR on multiple LANs.
11: What is the maximum age (MaxAge) of an IS-IS LSP?
** The MaxAge of an IS-IS LSP is 1200 seconds (20 minutes).
12: What is the basic difference between the way OSPF ages its LSAs and the way IS-IS ages its LSPs?
** OSPF increments the age up to MaxAge; IS-IS decrements the age down to 0. A new OSPF LSA has an age of 0, whereas a new IS-IS LSP has an age of MaxAge.
13: How often does an IS-IS router refresh its LSPs?
** The refresh rate of an IS-IS router is 900 seconds (15 minutes).
14: What is a Complete Sequence Number Packet (CSNP)? How is it used?
** A Complete Sequence Number Packet contains a full listing of all LSPs in a database. A CSNP is periodically sent by the Designated Router on a broadcast network to maintain database synchronization.
15: What is a Partial Sequence Number Packet (PSNP)? How is it used?
** A Partial Sequence Number Packet contains a listing of one or more LSPs. It has two uses: On point-to-point networks, it is used to acknowledge the receipt of LSPs. On broadcast networks, it is used to request LSPs.
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