Frequently Asked Questions of NAT & PAT
Got questions? We've got the answers quick, clear, and hassle-free as per mentioned FAQ
FAQ Execution
Dynamic routing automatically learns and updates routing table using routing protocols.
To provide automatic path selection, scalability, and failover.
RIP (Distance Vector), EIGRP (Hrbrid) and OSPF (Link-State).
Time taken for all routers to update and agree on network topology.
It reduces manual configuration and adapts to topology changes.
Large networks, inefficient protocols, and frequent topology changes.
A value used to determine the best path (e.g. hop count, bandwidth).
RIP: 120 , EIGRP: 90 (internal), 170 (external) and OSPF: 110
Using multiple paths to send traffic.
Using multiple paths with the same metric.
Using paths with different metrics (supported by EIGRP).
Sharing routes between different routing protocols.
A situation where packets circulate endlessly.
Using techniques like
1. Split horizon (Prevents sending route updates back through the same interface).
2. Route poisoning (Marking a route as unreachable).
3. Hold-down timers (Prevents routers from accepting incorrect updates for a period of time).
A distance-vector protocol using hop count as metric.
Simple routing in small networks (15 hop count only).
Classful (no subnet mask support) for Version 1 & Classless (Support VLSM AND CIDR).
Slow
A hybrid routing protocol (distance-vector + link-state features).
Fast convergence and efficient routing.
Bandwidth & Delay (Default), Reliability and Load.
Metric = [(10⁷ / min bandwidth) + delay] × 256
Backup route in EIGRP.
Reporting distance 'less than' Feasible distance.
= RD : Best metric to reach a destination.
= FD : Distance reported by a neighbor.
Distance reported by a neighbor.
Allows unequal-cost load balancing.
Medium to large enterprise networks or Enterprise networks needing fast convergence (Cisco based).
OSPF is a link-state dynamic routing protocol that calculates the shortest path to a destination using the SPF (Dijkstra) algorithm.
Scalable and hierarchical routing.
Cost = Reference Bandwidth / Interface Bandwidth.
100 Mbps (Default reference bandwidth)
Logical group of router and Area 0.
Information about network topology.
Requests specific link-state records from an OSPF neighbor.
Sends specific link-state records that were requested. This packet is like an envelope with multiple LSAs in it.
OSPF uses Link State Acknowledgement packets to confirm the receipt of Link-State Advertisements (LSAs), ensuring reliable delivery of routing information.
Relationship formed between routers to exchange routes.
Down → Init → 2-Way → ExStart → Exchange → Full.
Designated Router (Central router for LSA exchange in broadcast networks) and Backup Designated Router (Backup of DR).
Large, scalable, and multi-vendor (vendor-neutral) networks.
Efficient routing reduces congestion.
Network with single exit point.
Use OSPF for large networks, EIGRP for performance, RIP only for learning/small setups.
Inverse of subnet mask.
e.g. Wildcard = 255.255.255.255 – Subnet Mask
Combining routes at ABR/ASBR.
| Feature | RIP | EIGRP | OSPF |
|---|---|---|---|
| Type | Distance Vector | Hybrid | Link-State |
| Metric | Hop Count | Bandwidth + Delay | Cost |
| Formula | Hops | (10⁷/BW + Delay)×256 | Ref BW / BW |
| Max Size | Small | Medium-Large | Large |
| Convergence | Slow | Fast | Fast |
| Max. Hop | 15 | Unlimited | Unlimited |
| Vendor | Open | Cisco | Open |
