Nokia 4A0-114 - Nokia Border Gateway Protocol Fundamentals for Services

Understanding Path-ID: The BGP Path Identifier (Path-ID) is a concept used in BGP to support the advertisement of multiple paths for the same prefix without requiring multiple BGP sessions.

Path-ID Details:

Option A: Incorrect because the Path-ID is not pre-pended to the NLRI (Network Layer Reachability Information) field of a BGP update. It is part of the BGP Multipath feature and used to uniquely identify different paths.

Option B: Correct. Path-ID is an optional transitive attribute that allows for the advertisement of multiple paths.

Option C: Correct. Path-ID uniquely identifies each path advertised to a neighbor.

Option D: Correct. A BGP speaker that re-advertises a route must generate its own Path-ID.

Conclusion: Option A is false because it incorrectly describes the placement of the Path-ID.

References:

Nokia Border Gateway Protocol Fundamentals

RFC 7911 - Advertisement of Multiple Paths in BGP

Router R1 is a route reflector for its clients R2, R5, and R6.

The prefix 192.168.1.0/27 is advertised by Router R3 to Routers R5 and R6.

Router R5 will receive this prefix with a local preference of 200.

Since none of the routers in AS 65540 is configured with "advertise-external," Router R5 will not advertise the received external route to its internal peers.

The output of "show router bgp routes" on Router R5 will show the prefix 192.168.1.0/27 with a local preference of 200, learned from Router R3.

References

Nokia Border Gateway Protocol Fundamentals documentation

BGP Route Reflector and local preference configuration guidelines as per Nokia's documentation

The BGP import policy "north-and-south" on R5 checks the community attribute of incoming routes.

If the community matches "65200:1", it sets the local preference to 20.

Since R1 advertises the prefix 140.100.1.0/24 with a community of "65200:1", R5 will apply the policy action.

Therefore, the prefix's local preference is set to 20.

References:

Nokia Border Gateway Protocol Fundamentals documentation, Section 5.2 on BGP policies.

Local Preference Comparison: Local preference is the first criterion BGP uses to select the best path. The higher the local preference, the more preferred the route. Here, the first route has a local preference of 150, while the other two routes have a local preference of 100.

Best Path Selection: Since the first route has the highest local preference (150), it will be preferred over the other two routes regardless of the AS Path length or any other attributes.

RIB-Out: The RIB-Out (Routing Information Base - Outbound) contains the routes selected for advertisement to peers. As only the best path is advertised, only the first route with the highest local preference will be included in the RIB-Out.

References:

Nokia Border Gateway Protocol Fundamentals

RFC 4271 - A Border Gateway Protocol 4 (BGP-4)

Configuration Analysis: The provided image or configuration details are not visible, but generally, in such questions, the answer depends on the IP addresses and AS numbers involved.

BGP Session Types: BGP sessions can be iBGP (within the same AS) or eBGP (between different ASes). Without knowing the AS numbers of routers R2 and R3, it is impossible to determine whether the sessions are iBGP or eBGP.

Insufficient Information: Without the AS numbers and specific configuration details, it is not possible to definitively determine the type of BGP sessions.

References:

Nokia Border Gateway Protocol Fundamentals

Understanding BGP Configuration on Nokia Routers

The route-target (RT) value associated with a VPRN (Virtual Private Routed Network) is used to control the import and export of routes.

For the VPRN service depicted in the diagram, the RT value used between PE1 and PE2 must match the configured RT of the VPRN.

From the diagram, we see that the VPRN 400 is associated with the RT value 65200:400.

Therefore, the RT value included in the EVPN routes exchanged between PE1 and PE2 will be 65200:400.

References:

Nokia Border Gateway Protocol Fundamentals documentation, Section 7.5 on EVPN and VPRN route-target values.

EVPN (Ethernet VPN) VPLS (Virtual Private LAN Service) uses MP-BGP to exchange reachability information.

When PE1 and PE2 exchange MP-BGP route updates for VPLS 300, the addressing information included pertains to EVPN MAC addresses.

This is because EVPN uses MAC address learning over MP-BGP to provide the Layer 2 VPN service.

References:

Nokia Border Gateway Protocol Fundamentals documentation, Section 8.3 on EVPN route updates and MAC address learning.

A type-2 EVPN route update is used to carry host-specific information.

It includes the MAC address of the host and optionally the associated IP address.

This type of update allows for efficient MAC and IP address learning and advertisement within the EVPN.

Therefore, the type-2 EVPN route update carries a host MAC address and optionally the associated IP address.

References:

Nokia Border Gateway Protocol Fundamentals documentation, Section 11.2 on type-2 EVPN route updates.

Route Distinguishers (RDs) are used in BGP/MPLS VPNs to ensure unique VPN-IPv4 prefixes. Here are the characteristics of RDs:

A. True: An RD is prepended to an IPv4 prefix to form a VPN-IPv4 prefix.

B. True: An RD is used to indicate the VPRN service to which a route update is relevant.

C. True: A unique RD value is assigned to each VPRN service.

The false statement is:

D. False: An RD is a 64-bit value. In reality, an RD is a 96-bit value (composed of a 2-byte Type field and a 6-byte Value field).

ReferencesNokia Border Gateway Protocol Fundamentals, Chapter on Route Distinguishers and VPN-IPv4.