JN0-650 Exam Dumps : Enterprise Routing and Switching - Professional (JNCIP-ENT)

In Junos OS, the supplicant-mode configuration under protocols dot1x determines how the switch handles multiple MAC addresses on a single physical port. According to the exhibit, the current mode is set to Single, and the Number of connected supplicants is 2. This indicates that the port is currently allowing multiple devices, which contradicts the goal of limiting access to only one device at a time.

Here is the breakdown of why Option C is the correct solution based on Juniper’s standard behavior:

Supplicant Mode: Single (Current State): In this mode, the first device to authenticate opens the port for all subsequent devices. As long as the first device remains authenticated, other devices can send traffic through the port without individual authentication. This is why the exhibit shows 2 connected supplicants despite the mode being " Single. "

Supplicant Mode: Single-Secure (The Solution): This mode strictly limits the port to only one MAC address. Once a device successfully authenticates via 802.1X, the switch drops any traffic coming from any other MAC address on that port. If the authenticated device logs off or the session times out, the port becomes available for a new device, but never more than one simultaneously. * Supplicant Mode: Multiple (Option B): This mode allows multiple supplicants to authenticate individually. Each MAC address must go through its own authentication process. This would allow more than one device, which is the opposite of the user ' s requirement.

MAC RADIUS Restrict (Option A): This feature is used to force MAC-based authentication and does not inherently limit the number of devices to one in the same way that changing the supplicant mode does.

Maximum EAPOL requests (Option D): This parameter defines how many times the switch will send an EAP-Request/Identity frame to a supplicant before giving up. Changing this to 1 does not restrict the number of devices allowed on the port; it only changes the retry logic for a single authentication attempt.

Configuration Example for Junos OS 24.4: To implement this change, you would use the following command: set protocols dot1x edit interface ge-0/0/10.0 supplicant-mode single-secure

In BGP path selection, the Local Preference attribute is one of the most common ways to influence outbound traffic from an Autonomous System (AS). It is a well-known discretionary attribute that is propagated throughout the AS to tell internal routers which path is preferred for a specific destination.

Priority Rule: In the BGP selection algorithm, a higher local preference value is always preferred over a lower one. The default value in Junos OS is 100.

Influencing Outbound Traffic (Option A): To ensure that Provider A is always preferred, you would apply an import policy on R1 (the router connected to Provider A) to set the local preference of all received routes to a value higher than the default (e.g., 200). Since 200 > 100, R3 and R4 will prefer the path via R1.

Alternative Method (Option C): Conversely, you can achieve the same result by applying an import policy on R2 (the router connected to Provider B) to set the local preference to a value lower than the default (e.g., 50). Since the routes from R1 remain at the default of 100, and 100 > 50, the path via R1 (Provider A) is preferred.

Why B and D are incorrect: Setting a higher local preference on R2 (Option B) would make Provider B the preferred exit point. Setting a lower local preference on R1 (Option D) would make Provider A the least preferred exit point.

Junos OS 24.4 provides several server-failover options for 802.1X authentication to maintain network availability when the RADIUS server is unreachable.

Fallback Behavior (Option D): The use-cache fallback action allows the switch to consult its local cache of previously authenticated MAC addresses.

If a device was already authorized and its information is in the cache, the switch will continue to permit access based on those cached credentials.

However, if a new device (not in the cache) attempts to connect while the server is down, the switch cannot verify its credentials and will deny the access attempt. This matches the specific requirement to permit authorized devices while denying new ones.

Other Fallback Options:

permit (Option C): This would allow all devices (even new ones) to access the network, typically in a restricted " guest " or " bypass " VLAN.

deny (Option A): This would drop all traffic from all devices on the port if the server is unreachable.

vlan-name (Option B): This moves authenticated or unauthenticated users into a specific fallback VLAN.