4A0-112 Nokia IS-IS Routing Protocol Questions and Answers

In IPv6, consecutive sections of zeros can be abbreviated with a double colon (::) once in an address. Also, leading zeros in each hextet (group of four hexadecimal digits) can be removed.

The original address is2001:0da8:0000:0000:0024:0000:4ab9:0300.

Removing leading zeros and applying the abbreviation:

0da8becomesda8.

0000becomes0(and multiple consecutive 0000 sections can be represented by ::).

The final result becomes2001:da8::24:0:4ab9:300, which matches option A when properly formatted.

While configuring areference bandwidth(which is used to calculate link costs) can be useful, it is not strictly required for IS-IS to run. IS-IS uses default bandwidth values to calculate costs, and it can function without explicitly configuring a reference bandwidth.

When a router receives a CSNP (Complete Sequence Number PDU) that references an older LSP (Link-State PDU) than the one in its local database, it indicates that the neighbor is missing newer information.

In response, the router sends back a PSNP (Partial Sequence Number PDU) to the neighbor, which includes a copy of the LSPs it has in its local database that the neighbor may not yet have. This helps to synchronize the link-state information between routers.

In IS-IS, the Designated Intermediate System (DIS) is responsible for certain tasks on broadcast networks, such as generating link-state advertisements and acting as the central point for flooding information.

Typically, interfaces on a Nokia 7750 SR router are not configured in pairs on the same subnet for redundancy. Instead, redundancy is achieved through mechanisms like Virtual Router Redundancy Protocol (VRRP) or other high availability protocols, not by simply using interfaces in pairs on the same subnet.

From the output, we can see that theusagecolumn indicates whether a router is operating as an L1 or L2 router:

RoutersR1andR2have a usage ofL2, meaning they are L2 routers.

RoutersR3andR4have a usage ofL1, meaning they are L1 routers.

TheL1/L2designations refer to whether the routers participate in both Level 1 and Level 2 of IS-IS:

L1 routersonly communicate within their own area.

L2 routerscommunicate between areas.

In this case,R1andR2are L2 routers, andR3andR4are L1 routers.

In IPv6, the Neighbor Discovery Protocol (NDP) replaces the Address Resolution Protocol (ARP) used in IPv4. NDP is responsible for several functions, including resolving IP addresses to MAC addresses (similar to ARP), detecting duplicate IP addresses, and discovering other devices on the network.

IS-IS routers must have matching authentication settings to establish an adjacency. If one router is configured with authentication and the other is not, the routers will not be able to establish an adjacency because their authentication parameters do not match.

When an IS-IS router receives a newer LSP (Link-State PDU) than the one already in its database, it takes the following actions:

Updates its link-state database with the new LSP.

Acknowledges the LSP with a PSNP (Partial Sequence Number PDU), which is sent to the router that originated the LSP, confirming the receipt of the newer LSP.

Floods a copy of the updated LSP to its neighbors on other interfaces to ensure all routers in the network have the updated topology information.