Which three technologies improve high availability and convergence in a data center network? (Choose three.)

1. A. graceful restart (GR)
2. B. Bidirectional Forwarding Detection (BFD)
3. C. link loss adjacency
4. D. Failover Group (FG)
5. E. link aggregation group (LAG)

Correct Answer: ABE
High availability and fast convergence are critical in data center networks to minimize downtime and maintain optimal performance. The following technologies contribute to achieving these goals:
Graceful Restart (GR):
GR allows routers to maintain forwarding state during control plane restarts, ensuring continuous packet forwarding while minimizing network disruptions.
Bidirectional Forwarding Detection (BFD):
BFD provides fast detection of path failures, allowing routing protocols to converge quickly by detecting link failures much faster than traditional timers.
Link Aggregation Group (LAG):
LAG increases both redundancy and bandwidth by combining multiple physical links into one logical link, providing load balancing and fault tolerance.
Juniper Reference:
High Availability Techniques: These technologies are fundamental in ensuring rapid recovery and failover within Juniper-based data center environments.

Which two statements are true about how switches handle Layer 2 traffic? (Choose two.)

1. A. The MAC address is learned based on the destination MAC address.
2. B. The MAC address is learned based on the source MAC address.
3. C. Traffic is forwarded based on the source MAC address.
4. D. Traffic is forwarded based on the destination MAC address.

Correct Answer: BD
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.

Exhibit:

Referring to the exhibit, what is the route preference of the 172.25.11.254 next hop?

1. A. 5
2. B. 10
3. C. 130
4. D. 140

Correct Answer: A
In the exhibit, we see two next-hop addresses for the default static route (0.0.0.0/0):
The first next hop is172.25.11.254, with no specified preference.
The second next hop is172.25.11.200, with a specified preference of140.
Step-by-Step Breakdown:
Default Static Route Preference:If no preference is explicitly set for a next hop in Junos, it defaults to5for static routes.
Determining Preference:In this case, the next hop172.25.11.254does not have an explicit preference defined, so it will use the default value of5. The second next hop has a preference of140, which is higher,meaning it will only be used if the primary next hop is unavailable.
Juniper Reference:
Static Route Preference: In Junos, the default preference for static routes is5, and this value is applied unless overridden by the preference parameter.

Referring to the exhibit, why are the BGP routes hidden?

1. A. Load balancing is not enabled.
2. B. There are too many hops to the destination.
3. C. The BGP next hop is unreachable.
4. D. Other routes are selected because of better metrics.

Correct Answer: C
In the exhibit, the BGP routes are marked ashidden. This typically happens when the routes are not considered valid for use, but they remain in the routing table for reference. One common reason for BGP routes being hidden is that thenext hopfor these routes is unreachable.
Step-by-Step Breakdown:
BGP Next Hop:In BGP, when a route is received from a neighbor, thenext hopis the IP address that must be reachable for the route to be used. If the next hop is unreachable (i.e., the router cannot find a path to the next-hop IP), the route is marked as hidden.
Analyzing the Exhibit:The exhibit shows that the BGP next hop for all hidden routes is 10.4.4.4. If this IP is unreachable, the BGP routes from that neighbor will not be considered valid, even though they appear in the routing table.
Verification:
Use the command show route 10.4.4.4 to check if the next-hop IP is reachable.
If the next-hop is not reachable, the BGP routes will be hidden. Resolving the next-hop reachability issue (e.g., fixing an IGP route or an interface) will allow the BGP routes to become active.
Juniper Reference:
Junos Command: show route hidden displays routes that are not considered for forwarding.
Troubleshooting: Check the next hop reachability for hidden BGP routes using show route .

Leaf and spine data centers are used to better accommodate which type of traffic?

1. A. north-east
2. B. east-west
3. C. north-west
4. D. south-east

Correct Answer: B
In modern data centers, the shift toward leaf-spine architectures is driven by the need to handle increased east- west traffic, which is traffic between servers within the same data center. Unlike traditional hierarchical data center designs, where most traffic was "north-south" (between users and servers), modern applications often involve server-to-server communication (east-west) to enable services like distributed databases, microservices, and virtualized workloads.
Leaf-Spine Architecture:
Leaf Layer: This layer consists of switches that connect directly to servers or end-host devices. These switches serve as the access layer.
Spine Layer: The spine layer comprises high-performance switches that provide interconnectivity between leaf switches. Each leaf switch connects to every spine switch, creating a non-blocking fabric that optimizes traffic flow within the data center.
East-West Traffic Accommodation:
In traditional three-tier architectures (core, aggregation, access), traffic had to traverse multiple layers, leading to bottlenecks when servers communicated with each other. Leaf-spine architectures address this by creating multiple equal-cost paths between leaf switches and the spine. Since each leaf switch connects directly to every spine switch, the architecture facilitates quick, low-latency communication between servers, which is essential for east-west traffic flows.
Juniper's Role:Juniper Networks provides a range of solutions that optimize for east-west traffic in a leaf- spine architecture, notably through:
QFX Series Switches: Juniper??s QFX series switches are designed for the leaf and spine architecture, delivering high throughput, low latency, and scalability to accommodate the traffic demands of modern data centers.
EVPN-VXLAN: Juniper uses EVPN-VXLAN to create a scalable Layer 2 and Layer 3 overlay network across the data center. This overlay helps enhance east-west traffic performance by enabling network segmentation and workload mobility across the entire fabric.
Key Features That Support East-West Traffic:
Equal-Cost Multipath (ECMP): ECMP enables the use of multiple paths between leaf and spine switches, balancing the traffic and preventing any one path from becoming a bottleneck. This is crucial in handling the high volume of east-west traffic.
Low Latency: Spine switches are typically high-performance devices that minimize the delay between leaf switches, which improves the efficiency of server-to-server communications.
Scalability: As the demand for east-west traffic grows, adding more leaf and spine switches is straightforward, maintaining consistent performance without redesigning the entire network.
In summary, the leaf-spine architecture is primarily designed to handle the increase ineast-west trafficwithin data centers, and Juniper provides robust solutions to enable this architecture through its switch platforms and software solutions like EVPN-VXLAN.