While all options contain elements related to port security, the two absolute requirements are enabling MAC RADIUS authentication on the interface itself and applying a dynamic VLAN profile that tells the switch how to handle the RADIUS response. An access port with ethernet-switching is typical but not the only method (trunk with native VLAN could be used in some designs), and setting the port to trunk mode is incorrect for a standard access port scenario.

OSPF adjacency requires several parameters to match. While subnet masks and MTU can cause issues, a mismatch in OSPF network type is a very common culprit. Different network types use different multicast addresses for hello packets (224.0.0.5 vs. 224.0.0.6 for DR/BDR election) and have different default timers and neighbor discovery mechanisms, which will prevent adjacency from forming even if basic IP connectivity exists.

In Junos, when a policy evaluates routes ‘from protocol static’, it is evaluating the static routes that are present in the routing table. However, BGP (and the policy framework) by default only considers the active, best-path routes from the routing table for advertisement. A static route that is not the active best path (e.g., because another protocol has a better preference) will not be in the table for the policy to match and thus will not be advertised.

The key clue is that both hosts can ping their own default gateway (the switch’s SVI). This confirms layer 2 connectivity within each VLAN and basic SVI configuration. The next logical step is to check if the switch itself has the necessary route to forward packets between the subnets. The switch needs a route (either direct via the other SVI, or static/ dynamic) for the destination VLAN’s subnet. Checking the routing table (‘show route’) is the direct way to verify this.

For a GRE tunnel interface to be up/up, Junos requires that the tunnel destination IP address must be resolvable to a next-hop in the routing table. Simple ICMP reachability is not sufficient. The kernel must have a valid route (e.g., a static route or a route learned via a routing protocol) to reach the tunnel destination IP. Without this route, the tunnel interface’s underlying logical condition is not met, keeping it administratively down.

By default, a Junos switch interface configured with ‘family ethernet-switching’ is not a member of any VLAN. It is operationally inactive for data plane forwarding until it is explicitly assigned to an access VLAN (with ‘native-vlan-id’) or a trunk VLAN list (with ‘vlan members’). The ‘default’ VLAN (vlan-id 1) exists but ports are not members of it by default.

On multi-access networks, having every router form a full OSPF adjacency with every other router would create n*(n-1)/2 adjacencies and generate excessive LSA flooding. The DR/BDR mechanism solves this. The DR and BDR form adjacencies with all other routers (DROthers). DROthers only form adjacencies with the DR and BDR. This significantly reduces the number of adjacencies and controls the flooding of LSAs on the segment.

The loopback interface (lo0) in Junos is special. Firewall filters applied to lo0.0 are primarily used to protect the Routing Engine (RE). Therefore, they filter and can count traffic that is destined to or originated from the RE itself. This includes management traffic (SSH, SNMP), routing protocol updates destined to the device, and ICMP messages to the device’s IPs. It does not count transit data plane traffic, which is processed by the PFE and does not hit the lo0 interface.

In Junos, for a static route to be active in the routing table, its next-hop must be resolvable. This means the device must have a route to reach 192.168.1.1. If the next-hop is not directly connected and there is no route to it, the static route will be installed in the configuration but will remain in an ‘inactive’ state and not appear in the active routing table (‘show route’). You can verify this with ‘show route 0.0.0.0/0 inactive’.

While all options contain elements related to port security, the two absolute requirements are enabling MAC RADIUS authentication on the interface itself and applying a dynamic VLAN profile that tells the switch how to handle the RADIUS response. An access port with ethernet-switching is typical but not the only method (trunk with native VLAN could be used in some designs), and setting the port to trunk mode is incorrect for a standard access port scenario.0