Exhibit:
How many stages are shown in the exhibit?
The exhibit shows a Folded IP Clos Architecture, which is also referred to as a 3-stage Clos network design. This architecture typically consists of two layers of switches:
Spine Layer: The top row of switches.
Leaf Layer: The bottom row of switches.
Step-by-Step Breakdown:
Clos Architecture:
A 3-stage Clos network has two types of devices: spine and leaf. In this design, each leaf switch connects to every spine switch, providing a high level of redundancy and load balancing.
Stage Explanation:
Stage 1: The first set of leaf switches.
Stage 2: The spine switches.
Stage 3: The second set of leaf switches.
The Folded Clos architecture shown here effectively 'folds' the 3-stage design by combining the ingress and egress leaf layers into one, reducing it to two visible layers, but still maintaining the overall 3-stage architecture.
Juniper Reference:
IP Clos Architecture: The 3-stage Clos design is commonly used in modern data centers for high availability, redundancy, and scalability.
Exhibit:
Referring to the exhibit, what is the route preference of the 172.25.11.254 next hop?
In the exhibit, we see two next-hop addresses for the default static route (0.0.0.0/0):
The first next hop is 172.25.11.254, with no specified preference.
The second next hop is 172.25.11.200, with a specified preference of 140.
Step-by-Step Breakdown:
Default Static Route Preference:
If no preference is explicitly set for a next hop in Junos, it defaults to 5 for static routes.
Determining Preference:
In this case, the next hop 172.25.11.254 does not have an explicit preference defined, so it will use the default value of 5. The second next hop has a preference of 140, 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 is 5, and this value is applied unless overridden by the preference parameter.
When using spine and leaf fabric architectures, what is the role of each device? (Choose two.)
In a spine-leaf fabric architecture, which is commonly used in data center designs, each device has a distinct role to ensure efficient and scalable network traffic flow.
Step-by-Step Breakdown:
Spine Nodes:
The spine nodes form the backbone of the fabric and are responsible for transit traffic between leaf nodes. They connect to every leaf switch and provide multiple paths for traffic between leaf nodes, ensuring redundancy and load balancing.
Leaf Nodes:
The leaf nodes are used for host connectivity. These switches connect to servers, storage, or edge routers. They also connect to the spine switches to reach other leaf switches.
Juniper Reference:
Spine-Leaf Architecture: In Juniper's IP fabric designs, spine switches handle inter-leaf communication, while leaf switches manage host and endpoint connectivity.
You are troubleshooting a downed BGP session.
Referring to the exhibit, what is the cause of the problem?
The BGP session in the exhibit shows the state as Connect, which indicates that the TCP session between the BGP peers has not been fully established.
Step-by-Step Breakdown:
BGP State 'Connect':
The Connect state is the second stage in the BGP finite state machine (FSM). At this stage, BGP is trying to establish a TCP session with the peer, but the session has not yet been successfully established.
A successful TCP three-way handshake (SYN, SYN-ACK, ACK) is required before BGP can progress to the OpenSent state, where the peers exchange BGP Open messages.
Possible Causes:
A firewall blocking TCP port 179.
Incorrect IP addresses or network connectivity issues between the BGP peers.
Juniper Reference:
BGP Troubleshooting: In Junos, if a BGP session is stuck in the Connect state, the issue is likely due to a failure in establishing the underlying TCP connection.
What is the behavior of the default export policy for OSPF?
In Junos, the default export policy for OSPF is to reject all routes from being exported.
Step-by-Step Breakdown:
Default Export Policy:
By default, OSPF in Junos does not export any routes to other routing protocols or neighbors. This is a safety mechanism to prevent unintended route advertisements.
Custom Export Policies:
If you need to export routes, you must create a custom export policy that explicitly defines which routes to advertise.
Example: You can create an export policy to redistribute static or connected routes into OSPF.
Juniper Reference:
OSPF Export Behavior: In Juniper devices, the default policy for OSPF is to reject route advertisements unless explicitly configured otherwise through custom policies.
