Juniper Enterprise Routing and Switching Specialist (JNCIS-ENT) JN0-351 Exam Dumps: Updated Questions & Answers (April 2026)

BGP is a routing protocol that operates between autonomous systems (AS). An AS is a group of routers under a single administrative control. BGP can be classified into two types: internal BGP (IBGP) and external BGP (EBGP). IBGP is the BGP communication between routers within the same AS, while EBGP is the BGP communication between routers in different AS. BGP uses the AS_PATH attribute to record the AS numbers that the route has passed through, and uses it to prevent routing loops and select the best path.

In this scenario, you want to add a second ISP connection and remove the default route to the existing ISP. This means that you want to have more control over the routing decisions and use BGP to exchange routes with both ISPs. To do this, you need to deploy the BGP protocol in your network and configure both IBGP and EBGP sessions. The correct statements about BGP in this scenario are:

IBGP peers advertise routes received from EBGP peers to other IBGP peers. This is the default behavior of IBGP, as it allows the routers within the same AS to learn the routes from different EBGP peers and select the best exit point. However, IBGP has a rule that it does not advertise routes received from IBGP peers to other IBGP peers, to avoid creating routing loops. Therefore, option B is correct and option C is incorrect. To overcome this rule, IBGP requires a full mesh topology, where every IBGP router is directly connected to every other IBGP router, or a route reflector or confederation design, where some IBGP routers act as intermediaries to reflect or aggregate the routes to other IBGP routers.

EBGP peers advertise routes received from IBGP peers to other EBGP peers. This is the default behavior of EBGP, as it allows the routers in different AS to exchange routes and reachability information. However, EBGP has a rule that it does not advertise routes received from EBGP peers to other EBGP peers, to avoid creating routing loops. Therefore, option D is correct and option A is incorrect. To overcome this rule, EBGP uses the AS_PATH attribute to filter out the routes that contain its own AS number, or uses route maps or policies to control the route advertisement. IBGP does not update the next-hop attribute to ensure reachability within an AS, as the next-hop attribute is preserved by IBGP. Instead, IBGP relies on an underlying IGP (Interior Gateway Protocol) to provide reachability to the next-hop.

The static route to the 0.0.0.0/0 network has a next hop of xe-0/0/0.0, which is a local interface. BGP does not accept static routes with a local interface as the next hop, because it cannot advertise them to other BGP peers. BGP requires a valid IP address as the next hop for static routes that are redistributed into BGP. To fix this issue, the static route should have a next hop of an IP address that is reachable via the xe-0/0/0.0 interface, such as the IP address of the eBGP neighbor. Alternatively, the next hop can be modified by using a route map when redistributing the static route into BGP12.

The other options are not correct because:

The as-path parameter is not required for redistributing static routes into BGP. The as-path attribute is automatically set by BGP when advertising routes to other BGP peers3.

A community string is not required for redistributing static routes into BGP. A community is an optional attribute that can be used to group routes and apply policies to them4.

The no-readvertise feature is not specified in the configuration. The no-readvertise feature is used to prevent routes learned from one iBGP peer from being advertised to another iBGP peer5.

A RIB group is a configuration that allows a routing protocol to install routes into multiple routing tables in Junos OS. A RIB group consists of an import-rib statement, which specifies the source routing table, and an export-rib statement, which specifies the destination routing table or group.  A RIB group can also include an import-policy statement, which specifies one or more policies to control which routes are imported into the destination routing table or group 1 .

An import policy is a policy statement that defines the criteria for accepting or rejecting routes from the source routing table. An import policy can also modify the attributes of the imported routes, such as preference, metric, or community.  An import policy can be applied to a RIB group by using the import-policy statement under the [edit routing-options rib-groups] hierarchy level 1 .

Therefore, option A is correct, because an import policy is applied to the RIB group to control which routes are installed in the destination routing table or group. Option B is incorrect, because all routes in the source routing table are imported into the destination routing table or group, unless filtered by an import policy. Option C is incorrect, because a firewall filter is not used to install routes in the RIB groups; a firewall filter is used to filter packets based on various criteria. Option D is incorrect, because an export policy is not applied to the RIB group; an export policy is applied to a routing protocol to control which routes are advertised to other devices.

In OSPF, the Designated Router (DR) and Backup Designated Router (BDR) are elected based on the priority of the routers 1 .  The router with the highest priority becomes the DR, and the router with the second highest priority becomes the BDR 1 .  If there is a tie in priority, then the router with the highest Router ID is chosen 1 .

In this scenario, R2 has a higher priority (64) than R1 (32), so R2 will become the DR 1 .  Since R1 has the second highest priority, it will become the BDR 1 . Therefore, option D is correct.

The BGP attribute that you would use to forward all Internet traffic through the R1 device is the  local preference 1 .

The local preference is an attribute that is used within an autonomous system (AS) and exchanged between iBGP routers 1 .  It is used to select an exit point from the AS 1 .  The path with the highest local preference is preferred 1 .  By setting a higher local preference for the routes received from R1, you can make R1 the preferred exit point for all Internet traffic 1 .

To isolate management traffic in a non-default routing-instance on Junos-based devices, you can use the  set system management-instance  and  set routing-instances mgmt_junos  commands 1 2 .

set system management-instance : This command associates the management interface (usually named fxp0 or em0 for Junos OS, or re0:mgmt-* or re1:mgmt-* for Junos OS Evolved) with the non-default virtual routing and forwarding (VRF) instance 1 .  After you configure the non-default management VRF instance, management traffic no longer has to share a routing table with other control traffic or protocol traffic 1 .

set routing-instances mgmt_junos : This command creates a new routing instance named  mgmt_junos .  The name of the dedicated management VRF instance is reserved and hardcoded as  mgmt_junos ; you cannot configure any other routing instance by the name  mgmt_junos 1 .

Therefore, options C and D are correct.  Options A and B are not correct because they attempt to assign an interface to the  mgmt_junos  routing instance, which is not necessary for isolating management traffic 1 .

The default hello interval on an OSPF interface depends on the network type of the interface. For point-to-point and broadcast network types, the default hello interval is 10 seconds. For non-broadcast and point-to-multipoint network types, the default hello interval is 30 seconds. The hello interval is the time between sending hello packets to establish and maintain neighbor adjacencies. The hello interval can be configured manually on each interface using the  ip ospf hello-interval  command. References:

OSPF Hello and Dead Interval - NetworkLessons.com

OSPF Hello and Dead Interval: Operation and Configuration

Adjusting OSPF Timers - Cisco IOS Cookbook, 2nd Edition

ospf timer hello - WLAN AC V200R010C00 Command Reference - Huawei

OSPF Timers – Hello and Dead Intervals - Packet Lab

The maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation is 1476 bytes 1 .  This is because GRE packets are formed by the addition of the original packets and the required GRE headers 1 .  These headers are 24-bytes in length and since these headers are added to the original frame, depending on the original size of the packet we may run into IP MTU problems 1 .  The most common IP MTU is 1500-bytes in length (Ethernet) 1 .  When the tunnel is created, it deducts the 24-bytes it needs to encapsulate the passenger protocols and that is the IP MTU it will use 1 .  For example, if we are forming a tunnel over FastEthernet (IP MTU 1500) the IOS calculates the IP MTU on the tunnel as: 1500-bytes from Ethernet - 24-bytes for the GRE encapsulation = 1476-Bytes 1 .