What happens when a segment-routing TE tunnel loses the link and there is no secondary path in place?
Answer(s): A
In a Segment Routing Traffic Engineering (SR-TE) environment, when a TE tunnel loses its link and no secondary path is in place, the headend router dynamically computes a new path to the tail-end router. This computation considers available bandwidth and other constraints specified in the SR policy to determine the most optimal path. The Segment Routing mechanism then updates the label stack to reflect the new path, ensuring minimal disruption to traffic.This dynamic path computation and rerouting capability is a key feature of SR-TE, improving resiliency and efficiency in the network.
Refer to the exhibit. Routers R1 and R2 are part of a large enterprise network. The two devices are running BGP to advertise routes between them. The R1 Gi0/1 interface, which is connected to R2. is configured withthe next hop for all advertised prefixes' IP addresses. A network engineer noticed that R2 is not receiving certain routes from R1, which is causing connectivity issues. The engineer confirmed that the R2 IP address is reachable, and R2 is not filtering routes. Which action must the engineer take on R1 to resolve the issue?
Answer(s): B
The route-map DENY_ROUTES and prefix-list BLOCKED_ROUTES are correctly configured to filter specific routes (e.g., 10.3.3.0/24). However, the route map has not been applied under the BGP configuration on R1.This means the filtering logic is not in effect, allowing all routes to be sent to R2.To resolve the issue, the engineer must apply the route-map DENY_ROUTES under the BGP configuration on R1 using the command neighbor <R2 IP> route-map DENY_ROUTES out This ensures that the route-map is applied to outgoing BGP updates, filtering the specified routes as intended.Other actions (e.g., modifying sequence 10 or adding metrics) do not address the lack of route-map application.
In MPLS traffic engineering, which FRR operation swaps the label and pushes the backup label?
In MPLS Traffic Engineering (TE) with Fast Reroute (FRR), the Point of Local Repair (PLR) is the router where a failure is detected. The PLR immediately swaps the current label and pushes the backup label onto the packet stack to reroute traffic to a precomputed backup path. This operation ensures near-instantaneous recovery from link or node failures by directing traffic to the backup path without waiting for IGP convergence.
Refer to the exhibit. OSPF is running in the network, which is segmented into three areas. MPLS is enabled onall routers to support Layer 3 VPN. The network architect Is concerned about potential packet loss when new OSPF adjacencies form. Which two tasks should the architect perform to implement MPLS LDP synchronization? (Choose two.)
Answer(s): B,D
Enable LDP sync under the OSPF process:LDP synchronization ensures that MPLS Label Distribution Protocol (LDP) is fully operational before OSPF considers the link operational. This prevents traffic from being forwarded over a link that lacks MPLS labels, thus avoiding potential packet loss during OSPF adjacency formation.Enable MPLS on all interfaces involved in MPLS:All interfaces participating in MPLS forwarding must have MPLS enabled. This ensures that MPLS LDP labels are distributed properly across all paths in the network.
Refer to the exhibit. A service provider is running MPLS in the core to support Layer 3 VPN. OSPF is configured to support dynamic routing, and BGP is enabled throughout the network. A network engineer is adding a new P router to the infrastructure and is connecting it to P1 and P3. Which task must the engineer perform on the new router to allow it to participate in the Layer 3 VPN?
Answer(s): D
To integrate the new P router into the existing MPLS Layer 3 VPN infrastructure, the following steps are necessary:Configure OSPF:Ensure the new router establishes OSPF adjacencies with its neighbors (P1 and P3) in the same OSPFarea.OSPF will handle the IGP routing within the MPLS core.Enable MPLS:Enable MPLS on all interfaces participating in the core to allow Label Distribution Protocol (LDP) to establishlabel-switched paths (LSPs).BGP Configuration:Although the new router is a P (Provider) router and does not directly interact with customer routes, it needsto support MPLS forwarding for BGP-labeled routes between PE routers. BGP is used to advertise VPN routes among PE routers, and the P router ensures the MPLS labels are forwarded correctly.This configuration ensures that the new P router can participate in the MPLS core and forward VPN traffic without disrupting the existing Layer 3 VPN. Options like LDP sync and new OSPF areas are not necessary in this context.
Refer to the exhibit. Routers CE1 and CE2 support users in different locations, but the users require Layer 2 to operate within the company intranet. A pseudowire is configured between CE1 and CE2 to support these Layer 2 services. The connection is occasionally unstable, so an engineer has been asked to monitor it periodically. How should the engineer verify connectivity between sites over the Layer 2 connection?
MPLS OAM (Operations, Administration, and Maintenance):MPLS OAM provides tools for monitoring and troubleshooting MPLS networks.The LSP traceroute feature enables verification of connectivity along the Label Switched Path (LSP) used bythe pseudowire. This ensures the path is functional and traffic can traverse the Layer 2 connection.Why MPLS OAM for this scenario?A pseudowire uses MPLS to carry Layer 2 traffic over the core. MPLS OAM tools are specifically designedfor troubleshooting and validating MPLS paths.The LSP traceroute will confirm the integrity of the MPLS path and detect any issues between the endpoints.
Refer to the exhibit. PE1 and PE2 provide backbone carrier support to CSC-CE1 and CSC-CE2. CSC-CE1 and CSC-CE2 provide internet access and interoffice communication for CE1 and CE2, which are located at two different offices of an international corporation. CSC-CE1 and CSC-CE2 were recently moved to different autonomous systems from PE1 and PE2, and they must provide Layer 3 services to CE1 and CE2. Which task must the engineering team perform to allow CE1 and CE2 to continue to communicate through the two service providers?
In this scenario, the Customer Service Carrier (CSC) routers (CSC-CE1 and CSC-CE2) are now in different Autonomous Systems (AS) from PE1 and PE2. Unified MPLS is the most suitable approach to ensure seamless Layer 3 connectivity between CE1 and CE2 while maintaining scalability and inter-AS communication.Unified MPLS simplifies MPLS configurations across multiple autonomous systems by enabling label distribution and Layer 3 VPN services without extensive reconfiguration or loss of scalability.It allows the CSC routers to establish MPLS LSPs and enables seamless VPN traffic forwarding between PE1 and PE2.
What is the primary capability of Inter-AS VPN?
Inter-AS VPN is primarily designed to extend VPN services across multiple Autonomous Systems (AS) or service provider networks. This capability is critical when customers require connectivity between geographically dispersed sites served by different service providers or ASes.Key Features:End-to-End Connectivity:Enables seamless VPN service for customers whose networks span multiple service providers.Supports Layer 3 VPNs using MPLS, ensuring consistent communication between sites.Use Cases:Enterprises with global operations that rely on multiple ISPs to connect their branches.Service providers collaborating to deliver VPN services for mutual customers.
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