JN0-364: Service Provider Routing and Switching, Specialist (JNCIS-SP)Demo

The aggregate prefix 10.16.2.0/23 spans the address range from 10.16.2.0 through 10.16.3.255. Address 10.16.3.79 is within that range.

An incorrect peer IP address prevents the router from establishing the TCP connection to the intended BGP neighbor, so the BGP finite-state machine cannot progress to an established session. Juniper documents that inability to reach a peer’s IP address indicates a TCP transport connection problem, and that BGP returns to Idle when errors occur. Troubleshooting BGP Sessions | Junos OS | Juniper Networks

OSPF uses Dijkstra’s shortest-path-first (SPF) algorithm on a shared link-state database to calculate a loop-free shortest-path tree for the area.

The default IS-IS export policy rejects all routes. Routes must be explicitly accepted by a configured export policy before they are redistributed from the routing table into IS-IS.

vlan members 10 makes the interface a member of the VLAN whose VLAN ID is 10. With no trunk or tagged-access mode configured, the interface is an access interface, which accepts untagged traffic. A numeric VLAN member is a VLAN ID and does not indicate the VLAN’s name. Juniper documents that access interfaces accept untagged packets and that VLAN members may be specified by VLAN IDs.

IPv6 extension headers include the Hop-by-Hop Options header, Destination Options header, and Fragment header. The IPv6 base header has no header-checksum field, and “protocol” is not an IPv6 extension-header type.

Label Distribution Protocol (LDP) automatically distributes labels among MPLS routers and establishes the transport label-switched paths used across the MPLS domain. RSVP is used for explicitly signaled LSPs, BFD provides rapid failure detection, and BGP does not automatically create this LSP mesh.

A BGP router ID is a 4-octet, or 32-bit, unsigned identifier; IPv6 address families do not change its size. BGP supports 2-octet (16-bit) and 4-octet (32-bit) autonomous system numbers, so neither the 32-or-64-bit ASN statement nor the requirement for a 64-bit ASN is correct.

At the ingress LSR, the destination address identifies the forwarding equivalence class (FEC). The router then uses the label binding advertised by the next-hop LSR, R2, for that destination FEC. MPLS packets carry the label assigned by the neighboring downstream LSR for the FEC.

An RSVP-signaled LSP is configured using the label-switched-path statement at the [edit protocols mpls] hierarchy. The separate [edit protocols rsvp] hierarchy enables and configures RSVP signaling on interfaces.

An IBGP-learned route whose protocol next hop is a remote BGP neighbor must have that next hop resolved by another route. R2 advertises the EBGP-learned route with next hop 172.16.10.1, which R3 cannot resolve, making the route ineligible for forwarding and hidden. An IBGP export-policy action of next-hop self replaces the advertised next hop with R2’s local address for the BGP adjacency, allowing R3 to resolve it and install the route.

OSPF Database Description (DBD) packets exchange summaries of link-state advertisements while neighbors establish an adjacency, allowing each router to identify database information it needs from the other router.

Junos uses penultimate-hop popping by default: the egress router advertises implicit-null label 3, causing R4, the penultimate hop, to remove the MPLS label. R1 pushes the label at LSP ingress, while R3 is an intermediate transit router that replaces its incoming label with its outgoing label. Juniper: LSP Labels

RSVP-TE establishes MPLS LSPs with an Explicit Route Object (ERO), allowing traffic to be signaled across a specified sequence of core routers rather than being limited to the IGP shortest path.

The Initializing state indicates that a router has successfully received IS-IS hello packets from its neighbor but has not yet confirmed bidirectional hello reception. The adjacency becomes Up only after that confirmation. Cisco documents IS-IS adjacency states as Down, Initializing, and Up.

The BGP AS_PATH attribute records the autonomous systems through which route information has passed. It supports AS-loop detection by checking whether the local AS appears in the path, and its length is used in BGP best-path selection, with shorter AS paths preferred after higher-priority criteria. Route origin is conveyed by the ORIGIN attribute, while next-hop-device count is not represented by AS_PATH.

By default, iBGP advertises routes learned from eBGP peers to other iBGP peers, while an iBGP-learned route is not advertised to another iBGP peer; this split-horizon behavior prevents routing loops within an autonomous system. eBGP sessions advertise routes learned through either iBGP or eBGP to other eBGP peers, subject to normal BGP policy and loop-prevention processing.

Junos OS assigns aggregate routes a default preference value of 130. Juniper: Configuring Route Aggregation

Nonstop active routing (NSR) uses GRES while running and synchronizing routing protocol state on the backup Routing Engine. This preserves that state across a Routing Engine switchover without relying on neighboring helper routers, whereas graceful restart uses helper routers to restore protocol information.

The accept-data setting enables the VRRP primary router to accept packets addressed to the virtual IP address, allowing connected servers to ping the virtual gateway. In Junos, a higher-priority backup router preempts a lower-priority primary by default, so explicitly adding preempt is not required for the preferred router to resume the primary role.

An IS-IS LSP can carry multiple TLVs. The type-length-value format provides extensibility and flexible encoding of routing and other protocol information; it is not limited to IPv4.

All switches in an MSTP region must use the same MST region name, configuration revision number, and VLAN-to-instance mapping. Root bridge priority and root bridge ID are used in spanning-tree root election, not to establish MST region membership.

OSPFv3 supports IPv6 on interfaces without requiring IPv4 addressing. The OSPFv3 router ID is a unique 32-bit opaque value and is not a 128-bit IPv6 identifier.

AS-path prepending adds repeated instances of the local AS to routes advertised through the less-preferred EBGP link. The upstream AS sees a longer AS path for that route and can prefer the advertisement received through the other link, influencing traffic entering the local network. Cisco documents AS-path modification as a method to influence inbound path selection.