JN0-280 Exam Dumps - Juniper Certification Questions and Answers

When creating anIP fabric underlayusingOSPFas the routing protocol, consistentinterface speedsare important to ensure optimal traffic distribution and utilization of all links.

Step-by-Step Breakdown:

OSPF and Interface Speeds:OSPF calculates the cost of a link based on its bandwidth. The default cost calculation in OSPF is:

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If interface speeds vary significantly, OSPF may choose paths with lower cost (higher bandwidth), resulting in some links being underutilized.

Equal Utilization:To ensure that all links are equally utilized in an IP fabric, it is recommended to maintain uniform interface speeds across the fabric. This ensures balanced load sharing across all available paths.

Juniper Reference:

IP Fabric with OSPF: Juniper recommends consistent interface speeds to maintain even traffic distribution and optimal link utilization in IP fabric underlay designs.

When thediscardoption is configured as the next hop for a static route, it silently drops any packets that match the route without sending any notification to the sender.

Step-by-Step Breakdown:

Discard Behavior:

If a route uses thediscardnext hop, the router drops the packet without generating any ICMP message or error back to the sender. This is useful for creating null routes to prevent routing loops or blackhole traffic intentionally.

Reject vs. Discard:

Therejectnext hop, in contrast, drops the packet but sends anICMP Destination Unreachablemessage back to the source.

Juniper Reference:

Static Route Behavior: In Junos, thediscardoption ensures packets matching a static route are dropped silently, providing a way to discard traffic without alerting the source.

In Layer 2 switching, switches learn MAC addresses based on thesource MAC addressof incoming frames and forward frames based on thedestination MAC address.

Step-by-Step Breakdown:

MAC Learning:When a switch receives a frame, it records thesource MAC addressand the port on which it arrived. This allows the switch to know where to send traffic destined for that MAC address.

Forwarding Based on Destination:The switch then looks at thedestination MAC addressand forwards the frame out of the port associated with that MAC address. If the MAC is unknown, the switch floods the frame to all ports.

Juniper Reference:

Layer 2 Switching: Juniper switches use source MAC addresses to build MAC tables and forward traffic based on the destination MAC address.

EVPN (Ethernet Virtual Private Network)is a standard protocol used for building Layer 2 and Layer 3 VPNs over an IP or MPLS network. Thesignaling protocolused for EVPN isBGP(Border Gateway Protocol).

Step-by-Step Breakdown:

BGP as the EVPN Signaling Protocol:EVPN uses BGP to exchange MAC address reachability information between routers (PE devices). This enables devices to learn which MAC addresses are reachable through which PE devices, facilitating Layer 2 forwarding across an IP or MPLS core.

BGP Extensions for EVPN:BGP is extended with new address families (e.g., EVPN NLRI) to carry both MAC and IP address information, allowing for scalable and efficient multi-tenant network solutions.

Juniper Reference:

Junos EVPN Configuration: Juniper uses BGP as the control plane for EVPN to exchange MAC and IP route information between different data center devices.