BGP (Border Gateway Protocol)uses amulti-step decision processto select the best route among multiple paths. It doesnot use SPF or simple metrics like hop count.
Key BGP selection criteria include:
Local preference
AS path length
Origin type
MED (Multi-Exit Discriminator)
eBGP over iBGP
IGP metric to next hop
Option C is correct– BGP evaluatesmultiple attributesfor route selection.
[Reference:, Nokia IP Routing Fundamentals – BGP Route Selection, RFC 4271 – BGP Decision Process, ===========]
Question 2
Where would you expect to find a P router in a service provider's network?
Options:
A.
At the edge of the provider's network facing the customer.
B.
At the edge of the customer's network facing the provider.
C.
In the core of the provider's network.
D.
On the customer premises.
Answer:
C
Explanation:
AP router (Provider router)is locatedin the core of the service provider’s network. Its functions include:
ForwardingMPLS-labeled packetsbetweenPE routers.
Not interacting directly with customer routes or routing instances.
Having no knowledge ofVPN routing or customer-specific services.
Option C is correct– P routers sit in theMPLS core, isolated from customer edge.
[Reference:, Nokia MPLS and Services Guide – Core vs Edge Router Roles, Nokia SRA Study Guide – "PE and P Devices in MPLS", ===========]
Question 3
How does address summarization reduce the routing table size?
Options:
A.
By allowing a block of routes to be represented by one route.
B.
By only keeping the best routes in the routing table.
C.
By rejecting duplicate route advertisements.
D.
By not advertising directly connected routes.
Answer:
A
Explanation:
Address summarization(also called route aggregation) is a technique used in IP routing to combine several contiguous network prefixes into asingle summarized route.
This reduces the number of routes that need to be advertised and stored in routing tables, improvingscalability and performance.
Option A is correct– summarization replaces many specific routes with a single aggregated route.
Option Brefers to best path selection (not summarization).
Option Cis incorrect; duplicate advertisements are still processed and filtered based on metrics.
Option Dis unrelated to summarization; directly connected routes are always advertised unless specifically filtered.
[Reference:, Nokia IP Routing Study Guide – Chapter: “Route Aggregation and Scalability”, Cisco & Juniper Routing Principles – Route Summarization Best Practices, ===========]