Question 1

Recognizing true advantages of Network Address Translation (NAT) From the list below, identify the statements that represent real advantages of deploying NAT in an enterprise edge design (choose the correct grouping).

Accepted Answer

Introduction / Context:NAT translates private, non-routable address space to public addresses at the network edge. While NAT has trade-offs, it also offers concrete benefits that made it popular before widespread IPv6 adoption and continue to make it useful in many environments today. This question asks you to distinguish true advantages from known drawbacks.Given Data / Assumptions:Statements provided: (1) Translation introduces switching path delays. (2) Conserves legally registered addresses. (3) Causes loss of end-to-end IP traceability. (4) Increases flexibility when connecting to the Internet. (5) Certain applications will not function with NAT enabled. (6) Reduces address overlap occurrence.We must choose the grouping that lists only the advantages.Concept / Approach:NAT allows many internal hosts to share a limited set of public IPs, conserving registered address space (advantage). It also provides flexibility by abstracting internal addressing from service-provider assignments and changes (advantage). NAT helps when merging networks with overlapping private address spaces by translating one side to avoid conflicts (advantage). In contrast, NAT may complicate troubleshooting and break protocols that embed addresses or depend on end-to-end reachability (disadvantages).Step-by-Step Solution:Mark advantages: (2) conservation of public addresses; (4) flexibility for Internet connectivity and provider changes; (6) mitigation of overlapping address conflicts.Mark disadvantages: (1) added processing overhead/latency; (3) reduced end-to-end transparency/traceability; (5) application issues without NAT helpers or ALG.Select the grouping that includes 2, 4, and 6 only.Verification / Alternative check:Review common NAT use cases: PAT for many-to-one translation conserves public IPs; dual-homing or provider migration is simpler with NAT; mergers and acquisitions often rely on NAT to resolve overlapping RFC1918 deployments.Why Other Options Are Wrong:Options including 1, 3, or 5 list disadvantages, not advantages.Groupings without 2, 4, and 6 miss key benefits of NAT.Common Pitfalls:Assuming all NAT effects are beneficial; in reality, NAT can hinder troubleshooting and certain apps.Overlooking that NAT is not a security control by itself; it obscures addresses but does not replace a firewall.Final Answer:2, 4 and 6

Question 2

In Cisco NAT terminology, which term refers to the destination host's address as it appears on the inside network before any translation is applied (i.e., the destination address before translation)?

Accepted Answer

Introduction / Context:Understanding Network Address Translation (NAT) terms is essential for configuring and troubleshooting connectivity across private and public networks. Cisco uses four precise labels to describe addresses seen on either side of a NAT device: inside local, inside global, outside local, and outside global. This question focuses on the address that represents the destination host before translation as perceived on the inside network.Given Data / Assumptions:A NAT-enabled router separates an inside (private) network from an outside (typically public) network.The traffic flow is from an inside host to an outside destination.We are identifying the destination host's address before any translation, as seen on the inside.Concept / Approach:Cisco defines: inside local = inside host's pre-translation address; inside global = inside host's post-translation (globally routable) address; outside local = destination (outside) host's address as it appears within the inside domain (possibly translated); outside global = the outside host's true, globally routable address. The phrase “destination host before translation” from the perspective of the inside network corresponds to the outside local address.Step-by-Step Solution:Identify whose address is being described: the destination (outside host).Determine the vantage point: how the inside network views this destination prior to translation.Map the Cisco term: destination as seen inside, before translation => outside local.Confirm that inside local/global describe the inside host, not the destination.Verification / Alternative check:Examine NAT translation tables on a Cisco router (e.g., 'show ip nat translations') and note columns mapping inside local/global and outside local/global; the entry for the destination prior to translation is labeled outside local.Why Other Options Are Wrong:Inside local: This is the source (inside host) before translation, not the destination. Inside global: Inside host after translation. Outside global: The true public address of the destination as routable on the global Internet, not the inside's pre-translation view.Common Pitfalls:Confusing “inside vs. outside” with “local vs. global.” “Inside/Outside” refers to location relative to the NAT device; “Local/Global” refers to pre- vs. post-translation scope.Final Answer:Outside local

Question 3

Cisco NAT operations: Which IOS command shows real-time, live translation events occurring on the router?

Accepted Answer

Introduction / Context:Operational visibility is critical for troubleshooting NAT. While show commands reveal current state and counters, a live, event-by-event view helps diagnose intermittent or timing-related translation issues.Given Data / Assumptions:The router is performing NAT (static, dynamic, or PAT).You need to see translations as they are created or aged out.You are using Cisco IOS CLI.Concept / Approach:IOS 'debug' commands stream real-time activity to the console or VTY (with 'terminal monitor'). For NAT, 'debug ip nat' shows creation, hits, and timeouts of translations in real time. In contrast, 'show ip nat translations' displays the present table snapshot, and 'show ip nat statistics' gives counters and pool usage, not per-packet events.Step-by-Step Solution:Enable logging to your session if remote: 'terminal monitor'.Run 'debug ip nat' to start live translation output.Observe creation/matches/timeouts as traffic flows.When finished, stop with 'undebug all' or 'u all' to protect CPU.Verification / Alternative check:Correlate events with pings or application traffic while watching the debug output. Confirm entries appear in 'show ip nat translations' as the debug indicates.Why Other Options Are Wrong:show ip nat translations: Static snapshot, not live. show ip nat statistics: Summary counters only. clear ip nat translations *: Maintenance action to flush entries, not a display command.Common Pitfalls:Running debug on busy routers can affect performance; always turn off debugging after use.Final Answer:debug ip nat

Question 4

For an inside host in Cisco NAT, which term refers to its address before translation (the pre-translation address seen on the inside network)?

Accepted Answer

Introduction / Context:Cisco NAT terminology distinguishes between inside vs. outside and local vs. global. Correctly naming each address helps you configure rules, interpret translation tables, and resolve connectivity problems.Given Data / Assumptions:The focus is the inside host initiating traffic.We want the address before translation, as seen on the inside network.Standard Cisco NAT definitions apply.Concept / Approach:Inside local = inside host's private address (pre-translation). Inside global = the translated address representing the inside host on the outside. Outside local/global refer to the destination host as seen inside or globally, respectively.Step-by-Step Solution:Identify the subject: an inside host's pre-translation IP.Apply Cisco naming: inside + local => before translation, private scope.Therefore the correct term is inside local.Verification / Alternative check:Run 'show ip nat translations' during active sessions and locate the 'inside local' column; it lists the inside host's original private address.Why Other Options Are Wrong:Outside local/global: These refer to the external destination host. Inside global: This is the post-translation address used on the outside.Common Pitfalls:Confusing “local/global” with “private/public.” Local/global is about pre-/post-translation perspective, not necessarily RFC1918 status.Final Answer:Inside local

Question 5

Practical motivations for NAT deployment: Which scenarios are valid reasons to run NAT on your edge router?

Accepted Answer

Introduction / Context:NAT enables private networks to access public services without consuming large blocks of public IPv4 addresses. It also simplifies provider changes and allows overlapping address spaces to coexist during mergers.Given Data / Assumptions:(1) Need Internet access but hosts lack globally unique addresses.(2) New ISP requires renumbering; you prefer to avoid touching all endpoints.(3) You want zero Internet access for any host.(4) You must merge two intranets using duplicate address ranges.Concept / Approach:NAT/PAT maps many private addresses to one/few public addresses, supports provider independence (translate to the ISP's address block), and resolves overlapping spaces via translation between internal domains. If the goal is to block Internet entirely, NAT is irrelevant—use security controls instead.Step-by-Step Solution:Evaluate (1): Valid. NAT enables private-to-public access with PAT.Evaluate (2): Valid. NAT allows edge-only changes instead of renumbering all hosts.Evaluate (3): Not a reason. If no access is wanted, do not configure NAT and enforce filtering.Evaluate (4): Valid. NAT can translate between overlapping address domains.Verification / Alternative check:Review typical NAT use cases: Internet access with RFC1918, provider migration, and overlap remediation (e.g., VRF/NAT-virtualization combos).Why Other Options Are Wrong:2 and 4 / 3 only / All of the above: Include either too few valid scenarios or include the invalid scenario (3).Common Pitfalls:Misusing NAT as a security control. NAT is not a firewall; deploy ACLs or stateful inspection for policy enforcement.Final Answer:1, 2 and 4

Question 6

For an inside host in Cisco NAT, which term refers to its address after translation (the globally routable address representing the inside host)?

Accepted Answer

Introduction / Context:Correctly identifying NAT address roles prevents configuration mistakes and speeds troubleshooting. For inside-to-outside sessions, the inside host is represented on the public side by a translated address.Given Data / Assumptions:Inside host initiates traffic.We need the term for its post-translation address.Standard Cisco NAT vocabulary is used.Concept / Approach:Inside global is the translated, globally routable address that represents the inside host to the outside world. Inside local is the private, pre-translation address. Outside local/global describe the destination host as seen inside or globally.Step-by-Step Solution:Identify that we want the inside host's address after translation.Map to Cisco terms: inside + global => post-translation public-facing address.Hence, the correct answer is inside global.Verification / Alternative check:Run 'show ip nat translations' and note the 'inside global' column showing the public address bound to the inside host.Why Other Options Are Wrong:Inside local: Pre-translation. Outside local/global: Terms for the destination host, not the source inside host.Common Pitfalls:Assuming “global” always equals public Internet. It indicates the address visible outside the NAT boundary, which is typically public, but could be another routed domain.Final Answer:Inside global

Question 7

Operational visibility: Which IOS command shows all currently active NAT translations on the router (a snapshot of the present table)?

Accepted Answer

Introduction / Context:When validating NAT behavior, you often need to confirm which flows are translated and to what addresses. A command that lists the active entries is indispensable.Given Data / Assumptions:NAT is configured (static, dynamic, or PAT).Traffic has flowed so that translations exist.You want a point-in-time view, not a live debug feed.Concept / Approach:'show ip nat translations' displays the current translation table with columns for inside local/global and outside local/global. 'show ip nat statistics' summarizes counters and pool usage. 'debug ip nat' streams real-time events. 'clear ip nat translations *' deletes entries.Step-by-Step Solution:Run 'show ip nat translations' in privileged EXEC.Interpret columns to verify expected mappings.Use filters (e.g., pipe to include) if the table is large.Verification / Alternative check:Generate test traffic (ping/HTTP) and rerun the command; new entries should appear. Compare with 'show ip nat statistics' for aggregate counts.Why Other Options Are Wrong:show ip nat statistics: Summary only. debug ip nat: Real-time, not a static list. clear ip nat translations *: Destructive maintenance, not a display.Common Pitfalls:Assuming empty tables mean misconfiguration; idle timers may have aged entries out. Re-test with fresh traffic.Final Answer:show ip nat translations

Question 8

NAT drawbacks: Which items are recognized disadvantages of using NAT on a network edge device?

Accepted Answer

Introduction / Context:NAT solves address depletion and eases provider changes, but it comes with trade-offs. Understanding these disadvantages helps architects decide when NAT is appropriate or when alternatives (IPv6, policy routing, or application gateways) are better.Given Data / Assumptions:(1) Translation introduces switching path delays.(2) Conserves legally registered addresses.(3) Causes loss of end-to-end IP traceability.(4) Increases flexibility when connecting to the Internet.(5) Certain applications will not function with NAT enabled.(6) Reduces address overlap occurrence.Concept / Approach:True disadvantages: extra processing adds latency (1), NAT obscures original endpoints, hindering traceability and some security tools (3), and some protocols/applications break unless NAT-aware helpers or ALGs are used (5). Items (2), (4), and (6) are advantages, not drawbacks.Step-by-Step Solution:Identify costs: processing overhead => (1) true.Assess visibility/traceability: NAT hides endpoints => (3) true.Protocol compatibility: certain apps fail without helpers => (5) true.Discard advantages: (2), (4), (6) are benefits of NAT, not disadvantages.Verification / Alternative check:Measure latency before/after NAT, review logs where original IPs are masked, and test protocols like SIP, H.323, or active FTP without ALGs.Why Other Options Are Wrong:3 and 4 / 2, 4 and 5 / 1 and 3: These sets either include advantages or omit a true disadvantage.Common Pitfalls:Relying on NAT as a security feature. While it obscures addresses, it is not a substitute for proper firewalling and inspection.Final Answer:1, 3 and 5

Question 9

Cisco IOS NAT pools: Which command correctly creates a dynamic pool named 'Todd' that contains exactly 30 global addresses?

Accepted Answer

Introduction / Context:Defining the correct NAT pool requires matching the start/end addresses with an appropriate subnet mask so that the range falls within a valid network block. Here the pool must provide exactly 30 addresses.Given Data / Assumptions:Pool name must be 'Todd' (case sensitive in IOS context).Range: 171.16.10.65 through 171.16.10.94 inclusive.Required count: 30 addresses.Concept / Approach:A mask of 255.255.255.224 ('/27') yields a block size of 32 addresses per subnet: network .64 to .95. Usable host addresses are .65 through .94, which is exactly 30 usable addresses—matching the requirement and the provided range.Step-by-Step Solution:Compute /27 boundaries: increments of 32 (… .64–.95).Verify the specified range .65–.94 fits entirely inside .64–.95.Count usable addresses: 94 - 65 + 1 = 30.Select the mask /27 (255.255.255.224) with start/end .65 .94.Verification / Alternative check:Optionally, confirm with subnet calculators or by mental math of block sizes. /28 would only allow 14 usable addresses per subnet, not 30.Why Other Options Are Wrong:Option A (/28 .240): Too small (16 total, 14 usable). Option C: Wrong pool name case ('todd' ≠ 'Todd'). Option D (/24): Would imply 254 usable addresses, not 30, and range does not match full /24.Common Pitfalls:Forgetting that the pool's mask must encompass the entire start-end range and align to subnet boundaries.Final Answer:ip nat pool Todd 171.16.10.65 171.16.10.94 net 255.255.255.224

Question 10

Which Cisco IOS command provides a concise summary of the router's NAT configuration and counters (pool usage, translations, hits, misses)?

Accepted Answer

Introduction / Context:Beyond listing active translations, administrators often need aggregate information: total translations, misses, expired entries, pool allocations, and interface roles. A single command provides this summary view.Given Data / Assumptions:NAT is running on the router.You need an overview, not per-entry details or live debug.Concept / Approach:'show ip nat statistics' summarizes NAT health: total translations, peak counts, hits/misses, pool addresses in use/available, and which interfaces are configured as 'ip nat inside' or 'ip nat outside'. In contrast, 'show ip nat translations' lists per-flow entries only.Step-by-Step Solution:Run 'show ip nat statistics' in privileged EXEC.Review counters (total translations, misses) and interface roles.Check pool utilization to spot exhaustion problems.Verification / Alternative check:Correlate with 'show ip nat translations' to inspect specific flows if anomalies appear in statistics.Why Other Options Are Wrong:show ip nat translations: Per-entry detail, not a summary. debug ip nat: Real-time events only. clear ip nat translations *: Flushes entries; it does not display status.Common Pitfalls:Misreading peak vs. current counters; ensure you know whether values are cumulative or current.Final Answer:show ip nat statistics

Question 11

NAT not working: What is the best first troubleshooting step if your router is not translating addresses?

Accepted Answer

Introduction / Context:When NAT fails, the fastest fixes come from verifying foundational configuration: interface roles, ACLs that define interesting traffic, and route reachability. Random reboots or blanket debugging can waste time or harm stability.Given Data / Assumptions:Router configured to perform NAT/PAT.No translations are appearing.You have CLI access for checks.Concept / Approach:The most common NAT issues stem from interface mislabeling (missing 'ip nat inside' or 'ip nat outside'), wrong or empty ACLs used in 'ip nat inside source list', or routing that sends traffic around the NAT device. First confirm interface roles and correctness of the NAT rule bindings.Step-by-Step Solution:Check interface roles: 'show run | section interface' to ensure correct 'ip nat inside/outside' placement.Verify NAT rules: 'show run | include ip nat inside source' to confirm ACL/pool match.Confirm ACLs: 'show access-lists' to ensure the correct traffic is matched.Validate routing: make sure inside traffic actually traverses the NAT router.Verification / Alternative check:Generate test traffic, then use 'show ip nat translations' or 'debug ip nat' (with 'terminal monitor') to confirm translations appear.Why Other Options Are Wrong:Reboot / Call Cisco: Premature; basic checks often solve the issue. debug all: Dangerous—high CPU and overwhelming output; use targeted debug only after basics are verified.Common Pitfalls:Placing 'ip nat inside' and 'ip nat outside' on the wrong interfaces, or forgetting to apply them at all, is a classic cause of “NAT not working.”Final Answer:Check your interfaces for the correct configuration.

Question 12

Cisco NAT operations: Which Cisco IOS command clears all currently active Network Address Translation (NAT) translations on the router (i.e., flushes the entire NAT table)?

Accepted Answer

Introduction / Context:NAT (Network Address Translation) maintains a table of translations created as traffic flows through a Cisco router. During troubleshooting, you may need to flush all current entries to force new translations or to remove stale entries that cause connectivity issues. Knowing the exact command prevents accidental disruption or ineffective diagnostics.Given Data / Assumptions:You are working on a Cisco IOS router performing IPv4 NAT.The goal is to remove all active NAT translations immediately.You have appropriate privilege (enable) to run exec-level clearing commands.Concept / Approach:Cisco IOS provides the exec command family clear ip nat translations. Appending an asterisk clears the entire translation table in one action. Other commands such as show only display status and debug enables verbose logs but does not alter state.Step-by-Step Solution:Enter privileged EXEC mode (enable).Run: clear ip nat translations *Optionally verify emptiness with: show ip nat translationsMonitor re-creation of entries as traffic resumes.Verification / Alternative check:Immediately after execution, show ip nat translations should return no active entries (until new traffic arrives). show ip nat statistics reflects counters and active entries count dropping to zero.Why Other Options Are Wrong:show ip nat translations (A) only displays current entries.show ip nat statistics (B) displays counters and summary info.debug ip nat (C) enables debugging output but does not clear translations.Common Pitfalls:Forgetting that clearing the table can momentarily interrupt flows; using pattern-matched clears (specific inside/outside/local/global) when a full flush is intended; running the command during peak hours without change control.Final Answer:clear ip nat translations *

Question 13

Placing NAT roles on interfaces: On which interface should you configure the command that designates the “inside” of a private network for Cisco NAT?

Accepted Answer

Introduction / Context:Cisco NAT requires you to mark interfaces as either inside or outside. Correctly assigning these roles is essential so the router knows which direction to translate addresses and ports.Given Data / Assumptions:Private hosts reside on the LAN-facing interface(s).The router translates those hosts to public or upstream-reachable addresses when they access external networks.Standard IOS NAT configuration model is used.Concept / Approach:The LAN-facing interface connected to the private IPv4 space must be marked with ip nat inside. Conversely, the interface toward the public or upstream network is marked with ip nat outside. Terms like “inside local/global” and “outside local/global” are address types, not interface commands.Step-by-Step Solution:Interface toward private LAN → configure: ip nat insideInterface toward Internet/WAN → configure: ip nat outsideCreate static/dynamic/overload rules to perform translations.Verification / Alternative check:Use show ip nat statistics and show ip nat translations to confirm that traffic arriving on the inside interface is translated as expected.Why Other Options Are Wrong:ip nat outside (B) belongs on the WAN/upstream side.ip outside global (C) and ip inside local (D) are conceptual address categories, not interface configuration commands.Common Pitfalls:Reversing inside/outside designations; forgetting to apply ACLs or route-maps that define interesting traffic; assuming address type names are CLI commands.Final Answer:ip nat inside

Question 14

Recognizing NAT methods on Cisco IOS: Which listed items correspond to standard NAT methods supported on Cisco routers?

Accepted Answer

Introduction / Context:Cisco IOS supports several common NAT methods used for IPv4 address conservation and policy enforcement. Distinguishing the canonical methods helps you read and write configurations accurately and avoid misinterpreting terminology.Given Data / Assumptions:Items listed: 1) Static, 2) IP NAT pool, 3) Dynamic NAT, 4) double-translation, 5) Overload.We must select the set that represents recognized NAT methods.IOS classic NAT focus (not ASA twice NAT features).Concept / Approach:Classic IOS NAT methods are: Static NAT (one-to-one fixed mapping), Dynamic NAT (pool-based mapping allocated on demand), and NAT Overload (PAT, many-to-one with port multiplexing). “IP NAT pool” is a configuration element, not a separate method, and “double-translation” is not used as a formal IOS NAT method name in classic contexts.Step-by-Step Solution:Select Static (1) → valid method.Select Dynamic NAT (3) → valid method using a pool.Select Overload (5) → valid method (PAT).Verification / Alternative check:IOS configuration guides show syntax: ip nat inside source static, ip nat inside source list … pool …, and overload keyword for PAT. Pools support dynamic or policy NAT but are not a method by themselves.Why Other Options Are Wrong:Including “IP NAT pool” elevates a building block to a “method.”“Double-translation” is not a standard IOS term for a core method in this context.Common Pitfalls:Confusing PAT (overload) with dynamic NAT; treating address pools as a separate method rather than a resource used by dynamic or policy NAT.Final Answer:1, 3 and 5

Question 15

Defining a NAT pool: When creating a pool of global addresses on Cisco IOS, what keyword can be used instead of the netmask parameter to specify mask length?

Accepted Answer

Introduction / Context:Dynamic NAT typically requires defining a pool of global (translated) addresses. Cisco IOS lets you specify the pool's subnet mask either as a dotted-decimal netmask or by an alternative parameter. Knowing both forms is useful for speed and accuracy.Given Data / Assumptions:You are configuring ip nat pool for dynamic or policy NAT.You want to avoid typing a dotted-decimal mask.Standard IOS NAT syntax applies.Concept / Approach:The ip nat pool command supports either netmask a.b.c.d or prefix-length n, where n is the CIDR length (for example, 24 for 255.255.255.0). There is no slash notation in the command itself; you spell out prefix-length.Step-by-Step Solution:Enter global configuration.Define pool: ip nat pool NAME 203.0.113.10 203.0.113.50 prefix-length 27Reference the pool from a NAT rule and apply inside/outside on interfaces.Verification / Alternative check:Use show running-config to confirm that the pool reflects the intended prefix length. Test with live traffic or show ip nat translations.Why Other Options Are Wrong:Slash notation (A) is not literal CLI syntax for this command.“No mask” (C) would be invalid; a mask is required.“Block-size” (D) is unrelated to ip nat pool mask notation.Common Pitfalls:Typing area-style slash prefixes as in OSPF; mixing up pool prefix with inside interface subnet; forgetting to allow traffic with the correct ACL or route-map.Final Answer:prefix-length

Question 16

NAT terminology focus: In Cisco NAT terminology, which address represents the external (remote) destination host after translation occurs?

Accepted Answer

Introduction / Context:NAT terminology uses four named address types to describe how inside and outside hosts appear before and after translation. Correctly identifying these terms helps you read NAT tables and troubleshoot connectivity.Given Data / Assumptions:We focus on the destination host as seen from the inside after translation.Standard Cisco NAT definitions apply.Traffic flows from inside to outside.Concept / Approach:Outside global is the external host’s actual, routable address as seen from the NAT device (typically a public address on the Internet). Outside local would be the external host’s address as it appears inside, if translation of the outside address is performed (less common). Inside local and inside global describe the internal client’s pre- and post-translation identities.Step-by-Step Solution:Identify the remote destination host on the Internet.Determine its globally routable identity at the NAT boundary.Match this to the term “outside global.”Verification / Alternative check:Examine show ip nat translations: entries typically show Inside Local → Inside Global and Outside Local → Outside Global; the public remote server is represented as Outside Global.Why Other Options Are Wrong:Inside local/global identify the internal client pre/post translation.Outside local is an optional translated view of the remote host inside; not the canonical external destination identity.Common Pitfalls:Swapping “inside” and “outside” terms; assuming “local/global” denotes private/public for both sides uniformly without regard to translation perspective.Final Answer:Outside global

Question 17

PAT naming: Port Address Translation (PAT) is commonly referred to by which Cisco NAT term?

Accepted Answer

Introduction / Context:Port Address Translation allows multiple inside hosts to share one or a few public IPv4 addresses by multiplexing connections with different Layer 4 port numbers. Cisco refers to this feature using a specific keyword in NAT configuration and documentation.Given Data / Assumptions:You need the standard Cisco synonym for PAT.Classic IOS NAT syntax is used in examples.Understanding of static vs dynamic vs PAT is assumed.Concept / Approach:PAT is configured with the overload keyword in IOS, hence commonly called “NAT Overload.” Static NAT is a fixed one-to-one mapping, which is different. “NAT Fast” or “Overloading Static” are not formal features or terms.Step-by-Step Solution:Define ACL for inside traffic to translate.Reference interface or pool and add the keyword: overloadResult: many inside locals share one inside global with unique source ports.Verification / Alternative check:Use show ip nat translations to observe multiple entries sharing the same global address but using different source ports. Confirm counters with show ip nat statistics.Why Other Options Are Wrong:Static is not PAT; it is one-to-one mapping.“NAT Fast” and “Overloading Static” are not recognized configuration terms.Common Pitfalls:Forgetting the overload keyword; believing PAT works without inside/outside interface roles; overlooking firewall rules that block translated sessions.Final Answer:NAT Overload

Question 18

Placing NAT roles on the WAN: On the interface that connects a Cisco router to the Internet or upstream provider, which NAT role command should be applied?

Accepted Answer

Introduction / Context:A working NAT deployment requires correct designation of inside and outside interfaces. The upstream/WAN-facing interface must be marked appropriately so translations occur in the right direction when traffic leaves the private network.Given Data / Assumptions:The interface in question connects to the Internet or an upstream network.Classic IOS NAT is in use.Inside LAN hosts require translation to reach the outside.Concept / Approach:On a Cisco router, apply ip nat outside to the WAN interface and ip nat inside to the LAN interface. This informs the NAT engine which direction is outward versus inward for address/port mapping.Step-by-Step Solution:Enter interface configuration for the WAN port.Apply: ip nat outsideEnsure the LAN interface(s) are configured with: ip nat insideAdd NAT rules (static/dynamic/overload) to perform translations.Verification / Alternative check:show running-config should show correct inside/outside assignments. Use show ip nat translations while generating traffic to confirm outside-bound translations are created.Why Other Options Are Wrong:ip nat inside (A) is used on the private-side interface.ip outside global and ip inside local (C, D) are address type names, not interface commands.Common Pitfalls:Reversing roles; forgetting ACL/route-map references; omitting default route so translated traffic has no path outward.Final Answer:ip nat outside

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