ISIS

Question 1

What is the maximum and minimum length of the NET address

Answer 1

Maximum 20 bytes, minimum 8 bytes

Question 2

What are the two levels of adjacency?

Answer 2

L1 and L2

Question 3

Cisco IOS supports ISIS virtual link

Answer 3

False

Question 4

In level 1 redistribution is allowed

Answer 4

True

Question 5

Is Level 1 equivalent to OSPF stub area?

Answer 5

False, because in the stub area there are no external routes, Level 1 is equivalent to Totally not so stub area: Default route, Intra routes, Redistributed routes

Question 6

In practice the L1/L2 router does not announce default route at level 1

Answer 6

True, it only sets the attached bit in the Link state Packets LSP

Question 7

In the L1/L2 router there are two LSDBs, by default 1 per level

Answer 7

True

Question 8

In a network with routers configured as default, SPF is executed only once

Answer 8

False, by default routers are L1/L2 so SPF is executed once for each level

Question 9

L1 routes leak to L2 but L2 routes do not leak to L1 by default

Answer 9

True

Question 10

ISIS supports the same types of interfaces as OSPF

Answer 10

False, only Broadcast and P2P

Question 11

ISIS elects DIS and Backup DIS

Answer 11

False, there is no backup DIS

Question 12

Once DIS is elected there is the possibility of preemption

Answer 12

True, it occurs by high priority of the interface, or by SNPA which is basically the MAC address of the ISIS process

Question 13

Only one election occurs for both levels

Answer 13

False, two

Question 14

DIS is elected on both types of interfaces

Answer 14

False, only in Broadcast

Question 15

Adjacencies do not form in IP IP tunnels

Answer 15

True

Question 16

Areas must match only in L2 adjacencies

Answer 16

False, in L1 areas

Question 17

ISIS forms adjacencies on links of different network types

Answer 17

False

Question 18

ISIS forms adjacencies on links of different MTU types

Answer 18

False

Question 19

Default link cost is 10 and L2 routes are preferred over L1 routes

Answer 19

True, False

Question 20

Metric style wide is default and required for MPLS TE

Answer 20

False, narrow. True

Question 21

TLVs are used to encode metrics

Answer 21

True

Question 22

ISIS by default does not support MPLS TE

Answer 22

True, due to narrow metrics

Question 23

In case of metric style mismatch the adjacency does not come up

Answer 23

False, it comes up but the routes are not processed and do not appear in the RIB

Question 24

Metric style wide is mandatory for IPv6 support

Answer 24

True

Question 25

Neighbors running single and multi topology are compatible

Answer 25

False, adjacencies come up in IPv4 the routes are okay but the IPv6 routes are not

Question 26

In single topology it is possible to have different costs for IPv6 and IPv4

Answer 26

False, in multitopology

Question 27

In multitopology SPF is calculated twice

Answer 27

True

Question 28

The NET address 00.0000.0000.0001.00 is invalid

Answer 28

False, it is valid

Question 29

Passive interface lo0 without the ip router isis command allows the interface to be advertised

Answer 29

True

Question 30

Check the syntax redistribute isis level-2 into level-1 route-map PERMIT-ANY

Answer 30

missing ip parameter as below: redistribute isis ip level-2 into level-1 route-map PERMIT-ANY

Question 31

4 types of PDUs

Answer 31

•Hello PDU o ESH - End System Hello - Announces End Systems to an Intermediate system o ISH - Intermediate system Hello - Announces an Intermediate System (routers) to an End System o IS-IS Hello - Announcement between IS IS for adjacency formation • LSP PDU - Used to distribute link-state information • PSNP - Partial Sequence Number PDU - Used to ack missing parts of link state information • CSNP - Complete Sequence Number PDU :: Used to describe a complete list of LSP in the LSDB of a router

Question 32

LSP on P2P links are sent as ______, on broadcast networks are sent as _______

Answer 32

Unicast, Broadcast

Question 33

Level 1 and Level 2 adjacencies are not maintained via IIH o Default interval: ____ for non-DIS IS o For DIS the hello timer is ____ faster  To quickly detect DIS failures

Answer 33

10s, 3x

Question 34

If an LSP is valid and newer than the current one in the LSDB then it is accepted and timer set to ____ secs The timer is decremented sec by sec, when the value reaches 0 it is held for another ___ secs before being distributed as expired

Answer 34

1200, 60

Question 35

2 types of Sequence Number PDUs (SNPs): _____  Contains a summary of the entire LSDB  Routers exchange CSNP to compare their LSDBs  Periodically multicast every 10 Secs by the DIS on the LAN  On ptp links they are sent only initially after that only update LSPs which are acked by ______ o ______  Contains only a subset of LSP entries (like DBD?)  Are used to request transmission of missing or new LSPs

Answer 35

CSNP, PSNP, PSNP

Question 36

In single Topology the router does a consistent check and if the router does not have both address families configured then the v6 prefixes are not exchanged

Answer 36

True