JN0-649 Enterprise Routing and Switching Professional (JNCIP-ENT) Questions and Answers

Reviewing MST Configuration:

The configuration shown in the exhibit indicates MST (Multiple Spanning Tree) configuration for DS-1 and DS-2 switches.

For DS-1:

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mstp {

configuration-name Region-1;

revision-level 1;

interface ge-0/0/8;

interface ge-0/0/9;

interface ge-0/0/10;

interface ge-0/0/12;

msti 1 {

bridge-priority 4k;

vlan 10-19;

}

msti 2 {

bridge-priority 8k;

vlan 20-29;

}

}

For DS-2:

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mstp {

configuration-name Region-1;

revision-level 1;

interface ge-0/0/8;

interface ge-0/0/9;

interface ge-0/0/10;

interface ge-0/0/12;

msti 1 {

bridge-priority 8k;

vlan 10-19;

}

}

Understanding Bridge Priority:

In MSTP, the switch with the lowest bridge priority becomes the root bridge for the respective MST instance.

For MSTI 1:

DS-1 bridge-priority is 4k (4096)

DS-2 bridge-priority is 8k (8192)

Thus, DS-1 will be the root bridge for MSTI 1.

For MSTI 2:

DS-1 bridge-priority is 8k (8192)

DS-2 does not participate in MSTI 2.

Thus, DS-1 will be the root bridge for MSTI 2.

Analyzing VLAN Assignments:

DS-1 MSTI 1: VLANs 10-19, priority 4k

DS-1 MSTI 2: VLANs 20-29, priority 8k

DS-2 MSTI 1: VLANs 10-19, priority 8k

DS-2 does not have MSTI 2 configuration.

Conclusion:

DS-1 is the root bridge for MSTI 1 (C)

DS-2 does not participate in MSTI 2 (eliminates A)

DS-1 is the root bridge for MSTI 2 (D)

DS-2 is not the root bridge for MSTI 1 (eliminates B)

References:

Configuration snippets

Understanding of MSTP priorities and root bridge election

B - because only one next hop in forwarding table C- becuse TTL=1 limiting bgp connection to be established only over loopbacks interface https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/multihop-sessions.html Use the multihop statement to alter the default use of the neighbor ' s physical address. In addition, you can also specify a time-to-live (TTL) value in the BGP packets to control how far they propagate. We use a TTL value of 1 to ensure that the session cannot be established across any other backdoor links in the network.

The correct sequence for BGP active route selection when BGP multipath or multihop are not configured is as follows:

Higher local preference: Routes with a higher local preference are preferred.

Shortest AS path: Routes with the shortest AS path are preferred.

Lower origin code: Routes with lower origin code (IGP < EGP < Incomplete) are preferred.

Lowest router ID: Routes with the lowest router ID are preferred.

Lowest peer address: Routes with the lowest peer address are preferred.

References:

Standard BGP route selection criteria as outlined in network routing protocols.

Documentation from " Useful Juniper Commands.txt " and " Juniper Commands.pdf " which include detailed BGP operational commands and preferences​​​​.

Understanding the Configuration:

The provided configuration and output snippets show how traffic is classified and assigned to different forwarding classes based on the IP precedence values.

The inet-precedence classifier maps specific IP precedence values to forwarding classes with associated loss priorities.

Review of Classifiers:

IP Precedence Value 100:

The IP precedence value 100 in binary is represented as 100 (binary for 4).

Matching with Classifiers:

According to the configuration shown in the exhibit:

classifiers {

inet-precedence cos;

}

The classifier cos maps the following:

forwarding-class expedited-forwarding;

loss-priority low code-points 100;

Conclusion:

The IP precedence value 100 matches the expedited-forwarding forwarding class with low loss-priority as per the configuration.

To ensure that each host is placed on a separate VLAN when using an unmanaged switch between the hosts and the EX Series switch:

Configure an input firewall filter on interface ge-0/0/3 to match the source MAC or IP address of the hosts to assign the VLANs:

By configuring an input firewall filter, you can match the source MAC or IP address of incoming traffic and assign the appropriate VLAN based on these criteria.

This method ensures that even though the switch between hosts and EX Series is unmanaged, VLAN assignments are still properly enforced at the EX Series switch.

Configuration Example:

set firewall family ethernet-switching filter VLAN-assignment term VLAN100 from source-mac-address xx:xx:xx:xx:xx:xx

set firewall family ethernet-switching filter VLAN-assignment term VLAN100 then vlan-assignment vlan 100

set firewall family ethernet-switching filter VLAN-assignment term VLAN200 from source-mac-address yy:yy:yy:yy:yy:yy

set firewall family ethernet-switching filter VLAN-assignment term VLAN200 then vlan-assignment vlan 200

set firewall family ethernet-switching filter VLAN-assignment term VLAN300 from source-mac-address zz:zz:zz:zz:zz:zz

set firewall family ethernet-switching filter VLAN-assignment term VLAN300 then vlan-assignment vlan 300

set interfaces ge-0/0/3 unit 0 family ethernet-switching filter input VLAN-assignment

References:

The command references from " Useful Juniper Commands.txt " and network configuration guides provide details on firewall filters and VLAN assignments​​.

IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol used to move information efficiently within a computer network. Here is the detailed explanation about the statements:

Option A: IS-IS uses areas and an autonomous system.

This statement is correct. IS-IS organizes the network into a single autonomous system (AS), which can be divided into smaller groups called areas. Routing between areas is organized hierarchically. Each IS-IS network is treated as an autonomous system, and within that AS, multiple areas can be defined for efficient routing.

Option B: Level 1/2 routers automatically inject a default route to the nearest Level 1 router.

This statement is incorrect. Level 1/2 routers do not automatically inject default routes. Instead, they set the ATTACHED bit in their Level 1 link-state PDU when they can reach other areas, prompting Level 1 routers to use them as default gateways.

Option C: Level 2 routers must share the same area address.

This statement is incorrect. Level 2 routers operate across multiple areas and do not need to share the same area address. They are responsible for inter-area routing and thus work across different areas.

Option D: Level 1 routers route traffic between autonomous systems.

This statement is incorrect. Level 1 routers route traffic within a single area and forward inter-area traffic to Level 2 routers, which handle inter-area routing.

Conclusion Given the above explanations, the correct statement about IS-IS is:

A. IS-IS uses areas and an autonomous system.

This is based on the hierarchical structure of IS-IS routing where the network is divided into areas within a single autonomous system.

For further details, you can refer to the Juniper IS-IS Overview .

- Configure the local routing device so that it appears to be overloaded. You might do this when you want the routing device to participate in OSPF routing, but do not want it to be used for transit traffic. - Traffic destined to directly attached interfaces continues to reach the routing device. - When configured, the transit interface metrics are set to the maximum value of 65535. https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/ref/statement/overload-edit-protocols-ospf.html

https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospf-route-control.html#id-understanding-ospf-overload-function

The address range 232.0.0.0/8 is reserved for Source-Specific Multicast (SSM). This range is specifically allocated for SSM where data is sent from a specific source to the receivers.

References:

Source-Specific Multicast (SSM) Overview, RFC 4607

Reviewing POE Interface Information:

The exhibit shows the output of show poe interface and show poe controller commands.

The show poe interface command provides information about the PoE (Power over Ethernet) status on each interface.

Maximum Wattage Allocation:

The show poe controller output indicates that the maximum power available is 100 watts:

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Controller Maximum Power consumption Guard Management Status Lldp

index power band

0 100.00W 22.40W 10W Class AT_MODE Disabled

Thus, statement A is correct.

Power Consumption and Interface Priority:

The interface ge-0/0/11 has a high priority with a max power of 25.4W and current consumption of 11.4W:

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ge-0/0/11 Enabled ON 25.4W(L) High 11.4W 4

Given its high priority, ge-0/0/11 will continue to receive power even if the total power consumption exceeds 90 watts, as high-priority interfaces are less likely to be powered off when resources are low.

POE Status on Interfaces:

The ge-0/0/0 interface is shown as Enabled OFF , indicating PoE is not currently enabled.

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ge-0/0/0 Enabled OFF 15.4W Low 0.0W not-applicable

PoE+ Support:

The ge-0/0/10 interface has a power class of 4, which indicates support for PoE+.

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ge-0/0/10 Enabled ON 25.4W(L) Low 11.0W 4

References:

Exhibit output for show poe interface

Understanding PoE and PoE+ classes and priorities

Junos OS supports both underlay and ingress replication for BUM (Broadcast, Unknown unicast, and Multicast) traffic forwarding in EVPN-VXLAN deployments. Ingress replication is used for efficient multicast traffic distribution in networks where underlay multicast is not available.

References:

EVPN-VXLAN Configuration Guide, Juniper Networks

Juniper Networks Documentation on EVPN-VXLAN

 Captive Portal Functionality :

Captive portals are used to enforce user authentication by redirecting web browser requests to a login page until authentication is successful.

 Operation :

When a user connects to the network, their HTTP requests are intercepted and redirected to the captive portal login page. This process continues until the user provides valid credentials.

 Implementation :

Juniper Configuration :

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set security authentication-web redirect-url " http:// < captive-portal-url > "

set security zones security-zone < zone > interfaces < interface > host-inbound-traffic system-services http

set security zones security-zone < zone > interfaces < interface > host-inbound-traffic system-services https

set access profile < profile-name > captive-portal

This configuration ensures that all HTTP/HTTPS traffic is redirected to the specified captive portal for authentication.

 References :

Detailed configuration and operation are documented in " Tech Ops Managed Router Juniper Install Guide " and related documents​​​​.

802.1X Authentication and Re-authentication:

802.1X is used for network access control, where clients (supplicants) authenticate through a RADIUS server.

If a client cannot re-authenticate, the network access behavior depends on the configured action.

Permit Access Configuration:

The permit action ensures that the client continues to have network access if re-authentication fails.

This is crucial in scenarios where continuous access is needed despite temporary authentication issues.

Configuration Syntax:

On the Juniper device, configure the permit action:

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set protocols dot1x authenticator authentication-profile < profile > re-authentication permit

References:

Juniper documentation on 802.1X configuration

Understanding 802.1X re-authentication and access control mechanisms

In the given scenario, the connection between DC1 and DC2 is routed through a Layer 3 network. This indicates that the devices connecting the two data centers must be capable of performing Layer 3 routing to ensure that traffic can be properly forwarded across the network. Additionally, the use of VXLAN suggests that Integrated Routing and Bridging (IRB) functionality is required to enable communication between Layer 2 networks over the Layer 3 infrastructure.

The border devices (QFX10002) must handle Layer 3 routing to manage IP traffic between the data centers.

IRB functionality is necessary for routing between VLANs, allowing VXLAN to carry Layer 2 traffic across the Layer 3 network.

References:

The diagrams indicate the use of VXLAN for Layer 2 extension over a Layer 3 network.

The need for IRB is suggested by the presence of routed interfaces (IRB1 and IRB2) in the data center diagrams.

The " Tech Ops Managed Router Juniper Install Guide " provides insights into the Layer 3 routing capabilities and configurations necessary for such setups​​​​.

To implement fault-tolerant RPs (Rendezvous Points) in a multicast network, the following two solutions are appropriate:

Use MSDP with statically defined RPs:

MSDP (Multicast Source Discovery Protocol) is used to share multicast source information between multiple RPs in different domains or within the same domain. It allows for RP redundancy by ensuring that if one RP fails, another RP can take over the role and continue to manage multicast group memberships.