A BGP session in the Active state indicates the router is trying to initiate a TCP connection. Since IP reachability is confirmed, the next logical step is to verify that TCP port 179 (BGP) is not being blocked by a filter or firewall, which would prevent the three-way handshake from completing. Hold timer mismatches or authentication issues would typically cause the session to reach Established first, then fail.

The ‘resolve’ feature is used for static routes to make them conditional upon the reachability of the next-hop address. When configured, the static route is only installed in the routing table if the next-hop address is resolvable via an active route (e.g., through a dynamic protocol or another static route). A qualified-next-hop is for selecting among multiple next-hops, not for conditional installation.

The 2-Way state is a normal, stable state for OSPF neighbors on a broadcast network that are not the DR or BDR. It indicates that bidirectional communication has been established (Hello packets have been seen listing the local router’s RID), but they are not forming a full adjacency because they will only sync their LSDBs with the DR and BDR.

In Junos, routing protocols export routes from the routing table (RIB) into their protocol advertisements. To control which OSPF routes are advertised via BGP, you apply an export policy under the BGP protocol configuration (protocols bgp group export ). This policy evaluates routes from the RIB (which contains the OSPF routes) and decides which ones to advertise to BGP peers.

To enable per-packet load balancing for equal-cost multi-path (ECMP) routes in Junos, two configurations are required. First, you must set the maximum number of ECMP paths (e.g., ‘set routing-options multipath ecmp’). Second, you must configure the forwarding behavior by setting ‘set forwarding-options hash-key family inet layer-3’ and ‘set forwarding-options load-balance per-packet’. The ‘per-packet’ setting distributes packets round-robin across next-hops.

The loopback (lo0) interface is a virtual interface that is always up (as long as the router is operational), providing a stable IP address. Routing protocols like OSPF and BGP use the IP address assigned to lo0.0 (or the highest IP on a loopback) to derive the Router ID. It is also the preferred source/destination for protocol peering sessions, ensuring they don’t rely on the state of a physical interface.

In Junos firewall filters, if a packet passes through all configured terms without a match, it is handled by the implicit default action. This default action is always to ‘discard’ (silently drop) the packet. Therefore, a filter must have a final explicit term (e.g., ‘term accept-all’ with ‘then accept’) to permit any remaining traffic.

The ‘show route’ command family displays information from the Routing Information Base (RIB), which resides in the Routing Engine (RE). The ‘protocol static’ modifier filters the display to show only routes learned from the static routing protocol configuration. The Forwarding Table (FIB) is shown with commands like ‘show route forwarding-table’.

Every OSPF router generates a Type 1 Router LSA describing its own interfaces and neighbors within an area. A Type 2 Network LSA is generated *only* by the Designated Router (DR) on a multi-access broadcast or NBMA network. This Network LSA represents the multi-access network itself and lists all routers (including the DR) connected to it.

A BGP session in the Active state indicates the router is trying to initiate a TCP connection. Since IP reachability is confirmed, the next logical step is to verify that TCP port 179 (BGP) is not being blocked by a filter or firewall, which would prevent the three-way handshake from completing. Hold timer mismatches or authentication issues would typically cause the session to reach Established first, then fail.0