4A0-100 Exam Dumps - Nokia IP Networksand Services Fundamentals

VLAN Stacking, also known asQ-in-Q tunneling, is a technology that allowsmultiple customers to use overlapping VLAN IDswhile being transported over ashared service provider network.

Key Concepts:

Customer VLAN (C-VLAN):The VLAN used by the customer in their own network.

Service VLAN (S-VLAN):The VLAN used by the service provider to encapsulate the customer VLAN.

When VLAN stacking is applied:

A customer's Ethernet frame already tagged with aC-VLANisencapsulated with an additional outer S-VLAN tag.

This way,multiple customers can use the same C-VLAN ID, but remain isolated by theunique S-VLANassigned to them by the service provider.

Why Other Options Are Incorrect:

A. VLAN Trunking:Used to carry multiple VLANs over a single physical link but doesn’t allow reuse of VLAN IDs across customers.

C. VLAN Tagging:Refers to the general process of adding a VLAN tag; it doesn't provide the isolation needed across shared infrastructure.

D. VLAN Routing:Refers to Layer 3 routing between VLANs, not to ID reuse or transport over a shared provider backbone.

Thesystem interfacein Nokia SR OS is aloopback-style logical interfacethat represents therouter itself. It is used for:

Router ID assignment (if not manually set)

Source IP for control-plane protocols (OSPF, BGP)

Reachability testing

Important properties:

It istype loopback✔

Itexists by default✔

If router ID is unset, it uses thesystem IP address✔

Butthe IP address on the system interfacedoes not need to be /32❌

It can haveother prefix lengths, especially in service provider scenarios.

Thus, Option B is FALSE.

In MPLS architecture, theIngress LER (Label Edge Router)is responsible for:

Pushing labelsonto unlabeled packets and injecting them into the MPLS domain.

Acting as thestarting point of the Label Switched Path (LSP).

From the diagram:

R1is thestarting point (Ingress LER)for both LSP A and LSP B.

R4is theEgress LER, which wouldpopthe labels at the end of the LSP.

So,R1 is responsible for label push (imposing)at the start of both LSPs.

Option A is correct– R1 pushes labels for both LSP A and LSP B.

Option Bis incorrect – R4 is an egress router, not ingress.

Option C/Dare incorrect – the LSPs both start at R1.

TheDHCP client/server exchangefollows a specific four-step sequence known asDORA:

Discover– Client broadcasts to find available DHCP servers.

Offer– DHCP server responds with an IP address offer.

Request– Client requests the offered IP.

Acknowledgement– Server confirms the lease.

This ensuresdynamic IP configurationand is used in enterprise and home networks.