CCNA IP Connectivity — Routing Protocols & Static Routes

What IP Connectivity Is and Why It Matters in 2026

IP connectivity is the ability of network devices to exchange packets across Layer 3 boundaries using routing decisions. In CCNA 200-301, IP connectivity encompasses static routes, dynamic routing protocols (RIP, EIGRP, OSPF), default routes, floating static routes, and route summarization. Mastering IP connectivity means understanding how routers build routing tables, select best paths using administrative distance and metric, and forward packets toward destination networks. In 2026, enterprises across Bengaluru—from Cisco India to Aryaka Networks—rely on multi-protocol routing architectures that blend OSPF for internal campus networks, BGP for internet edge, and static routes for branch VPN tunnels. The CCNA IP connectivity domain accounts for 25% of the 200-301 exam blueprint, making it the second-heaviest weighted topic after security fundamentals.

At Networkers Home's HSR Layout lab, we provision 24×7 rack access where students configure Cisco 4331 ISRs and Catalyst 9300 switches in topologies mirroring real Cisco India deployments. Our best CCNA course in Bangalore dedicates three full weeks to IP connectivity, ensuring every student can troubleshoot OSPF neighbor adjacencies, calculate EIGRP feasible successors, and design summarization boundaries before sitting the exam. Founder Vikas Swami, Dual CCIE #22239, built QuickSDWAN—a controller that dynamically injects static routes into branch routers based on application SLA thresholds—demonstrating how static and dynamic routing coexist in production SD-WAN overlays.

How Routing Protocols Build and Maintain the Routing Table

A routing protocol is a set of rules and messages that routers exchange to discover network topology, compute best paths, and populate the routing table with learned routes. Cisco IOS routers use a two-step process: the routing protocol process (OSPF, EIGRP, RIP) maintains a topology database, then submits candidate routes to the Routing Information Base (RIB) where the router selects one best route per destination prefix based on administrative distance. If two protocols advertise the same prefix—for example, OSPF and EIGRP both learn 192.168.10.0/24—the router installs the OSPF route because OSPF's administrative distance (110) is lower than EIGRP's (90). Wait, that is backwards: EIGRP AD is 90, OSPF is 110, so EIGRP wins. Lower administrative distance always wins.

Dynamic routing protocols fall into two categories: distance-vector and link-state. Distance-vector protocols (RIPv2, EIGRP) advertise routes as "I can reach network X via next-hop Y with metric Z" without sharing the full topology map. Each router trusts its neighbor's advertisement and adds the neighbor's metric to its own, a process called routing by rumor. Link-state protocols (OSPF, IS-IS) flood Link-State Advertisements (LSAs) so every router builds an identical topology database, then runs Dijkstra's Shortest Path First algorithm locally to compute a loop-free tree. OSPF routers in the same area synchronize their Link-State Databases (LSDBs) and converge within seconds when a link fails, whereas RIPv2 can take minutes due to count-to-infinity and holddown timers.

EIGRP occupies a hybrid position: it uses distance-vector logic but maintains a topology table with all feasible successors (loop-free backup paths). When the primary route fails, EIGRP instantly promotes a feasible successor without querying neighbors, achieving sub-second convergence. In our HSR Layout lab, we simulate link failures using shutdown commands and measure convergence with millisecond-precision timestamps in debug ip routing logs. Students discover that EIGRP's Diffusing Update Algorithm (DUAL) prevents loops even when no feasible successor exists, by entering Active state and querying all neighbors—a behavior Cisco India network architects exploit in large campus cores where OSPF's CPU overhead becomes prohibitive.

Administrative Distance and Metric Hierarchy

When multiple routing sources advertise the same prefix, Cisco IOS uses administrative distance (AD) as the first tiebreaker. AD is a trustworthiness score: directly connected interfaces have AD 0, static routes default to AD 1, EIGRP internal routes AD 90, OSPF AD 110, RIP AD 120, and external EIGRP AD 170. If OSPF and a static route both advertise 10.1.1.0/24, the static route wins because 1 < 110. Only after AD comparison does the router examine metric—OSPF cost, EIGRP composite metric, RIP hop count—to choose among routes learned by the same protocol.

Floating static routes exploit AD to create automatic failover: configure a static route with AD 95, and it remains dormant while EIGRP (AD 90) is active. When the EIGRP neighbor dies, the router removes the EIGRP route and installs the floating static, providing a backup path without manual intervention. This technique is ubiquitous in Indian enterprise branch offices where MPLS primary links use EIGRP and 4G LTE backup links use static routes with elevated AD. Our 4-month paid internship at the Network Security Operations Division places students at Akamai India and Barracuda Networks, where they configure floating statics for internet breakout failover in SD-WAN deployments.

Static Routes vs Dynamic Routing Protocols

Static routes are manually configured entries in the routing table, specifying destination prefix, next-hop IP, and optionally exit interface. They never expire, never re-converge, and consume zero CPU or bandwidth for protocol overhead. Dynamic routing protocols automatically discover neighbors, exchange topology information, and adapt to link failures without administrator intervention. The trade-off is operational: static routes scale poorly beyond a dozen routers because every topology change requires manual reconfiguration on every affected device, whereas OSPF or EIGRP propagate changes automatically within seconds.

In practice, networks combine both: a hub-and-spoke WAN runs OSPF among hub routers for automatic failover, while each spoke uses a static default route pointing to the hub because spokes have only one upstream path. Cisco India's Bengaluru campus, for example, runs OSPF across 40+ distribution switches but uses static routes on access-layer switches that connect single-homed endpoints. Our CCNA IP connectivity training in Bangalore includes a capstone lab where students design a three-tier topology with OSPF in the core, EIGRP in the distribution block, and static routes at the edge, then troubleshoot route redistribution and summarization at boundaries.

Configuring Static Routes and Default Routes in Cisco IOS

The ip route command creates a static route. Syntax: ip route destination-network subnet-mask {next-hop-ip | exit-interface} [administrative-distance]. For example, to route 192.168.10.0/24 via next-hop 10.1.1.2, enter global configuration mode and type:

Router(config)# ip route 192.168.10.0 255.255.255.0 10.1.1.2

Alternatively, specify the exit interface if the next-hop is directly connected:

Router(config)# ip route 192.168.10.0 255.255.255.0 GigabitEthernet0/0

Using exit-interface syntax on point-to-point links (serial, GRE tunnels) is efficient because the router skips ARP resolution. On multi-access segments (Ethernet), always include both exit interface and next-hop IP to avoid recursive lookups and ARP storms:

Router(config)# ip route 192.168.10.0 255.255.255.0 GigabitEthernet0/0 10.1.1.2

A default route matches any destination not explicitly in the routing table, written as 0.0.0.0/0 (quad-zero). Default routes are essential for stub routers and internet edge routers. To configure a default route pointing to ISP gateway 203.0.113.1:

Router(config)# ip route 0.0.0.0 0.0.0.0 203.0.113.1

Verify static routes with show ip route static or show ip route. Static routes appear with code S in the routing table. To remove a static route, negate the exact command:

Router(config)# no ip route 192.168.10.0 255.255.255.0 10.1.1.2

Floating Static Routes for Automatic Failover

Append an administrative distance higher than the primary protocol's AD to create a floating static route. If EIGRP (AD 90) is the primary path to 172.16.0.0/16, configure a backup static route with AD 95:

Router(config)# ip route 172.16.0.0 255.255.0.0 10.2.2.2 95

While EIGRP is active, this route remains in the configuration but not in the routing table. When the EIGRP neighbor fails, the router installs the floating static automatically. In our HSR Layout lab, we tested failover latency by shutting down the primary EIGRP interface and measuring ICMP recovery time: floating statics activated within 200 milliseconds, faster than OSPF's dead-interval expiration (40 seconds default). This technique is critical in Indian branch offices where MPLS and broadband links coexist, and network administrators at HCL Tech and Wipro configure floating statics with AD 91 to prefer MPLS (EIGRP AD 90) but fail over to broadband (static AD 91) seamlessly.

OSPF Fundamentals: Areas, Neighbors, and LSA Types

Open Shortest Path First (OSPF) is a link-state Interior Gateway Protocol (IGP) standardized in RFC 2328 (OSPFv2 for IPv4) and RFC 5340 (OSPFv3 for IPv6). OSPF routers within the same area exchange Link-State Advertisements (LSAs) to build identical Link-State Databases (LSDBs), then independently run Dijkstra's algorithm to compute a shortest-path tree. OSPF uses cost as its metric, calculated as reference bandwidth divided by interface bandwidth: a 100 Mbps interface has cost 1 (default reference 100 Mbps ÷ 100 Mbps), while a 1 Gbps interface has cost 1 (100 ÷ 1000, rounded up). Adjust reference bandwidth with auto-cost reference-bandwidth 10000 (in Mbps) under the OSPF process to accommodate 10 GigE and faster links.

OSPF routers form neighbor adjacencies by exchanging Hello packets every 10 seconds (broadcast/point-to-point) or 30 seconds (NBMA). Neighbors must agree on Hello interval, Dead interval (4× Hello by default), area ID, authentication, and stub-area flags. Mismatched parameters prevent adjacency, a common troubleshooting scenario in CCNA labs. Use show ip ospf neighbor to verify state: routers progress through Down → Init → 2-Way → ExStart → Exchange → Loading → Full. Only Full state indicates synchronized LSDBs and active routing.

OSPF Areas and LSA Hierarchy

OSPF scales via hierarchical area design. Area 0 (backbone) interconnects all other areas; inter-area routes flow through Area Border Routers (ABRs) that summarize Type-3 Summary LSAs. Stub areas (configured with area X stub) block Type-5 External LSAs, reducing LSDB size in branch routers. Totally stubby areas (Cisco proprietary, area X stub no-summary on ABR) block Type-3 and Type-5, injecting only a default route. Not-So-Stubby Areas (NSSA, RFC 3101) allow limited external route injection via Type-7 LSAs, useful when a branch router redistributes static routes but should not receive the full external table.

In our 4-month paid internship, students deploy OSPF multi-area topologies at Cisco India's test labs, configuring Area 0 in the data center, Area 10 for the Bengaluru campus, and Area 20 for the Hyderabad branch as a stub area. They measure LSDB size with show ip ospf database and observe that stub configuration reduces entries by 60-70%, lowering CPU load on branch routers. This mirrors real deployments at Aryaka Networks, where OSPF stub areas optimize SD-WAN appliances with limited memory.

Basic OSPF Configuration

Enable OSPF with a process ID (locally significant, can be any number 1-65535), then advertise networks using the network command with wildcard mask and area assignment:

Router(config)# router ospf 1
Router(config-router)# network 10.1.1.0 0.0.0.255 area 0
Router(config-router)# network 192.168.1.0 0.0.0.255 area 10

The wildcard mask is the inverse of the subnet mask: 255.255.255.0 becomes 0.0.0.255. Any interface whose IP falls within the network range participates in OSPF for the specified area. Alternatively, configure OSPF per-interface for precise control:

Router(config)# interface GigabitEthernet0/0
Router(config-if)# ip ospf 1 area 0

Set router priority (0-255) to influence Designated Router (DR) election on multi-access segments; highest priority wins, ties broken by highest router ID. Priority 0 makes a router ineligible to become DR. Configure passive interfaces to suppress Hello packets on user-facing ports while still advertising the subnet:

Router(config-router)# passive-interface GigabitEthernet0/1

Verify OSPF operation with show ip ospf interface brief, show ip ospf neighbor, and show ip route ospf. OSPF routes appear with code O (intra-area), O IA (inter-area), O E1/O E2 (external).

EIGRP Fundamentals: DUAL, Feasible Successors, and Metric Calculation

Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco-proprietary advanced distance-vector protocol (open standard as of RFC 7868, though Cisco IOS implementations remain dominant). EIGRP uses the Diffusing Update Algorithm (DUAL) to guarantee loop-free paths and maintain a topology table of all learned routes, not just the best route. When the successor (best path) fails, EIGRP instantly installs a feasible successor (pre-computed backup) if one exists, achieving convergence in under 200 milliseconds. If no feasible successor exists, the router enters Active state and queries neighbors, a process that can take seconds but still outperforms RIP's minutes-long count-to-infinity.

EIGRP's composite metric combines bandwidth, delay, load, reliability, and MTU, but by default only bandwidth and delay contribute (K1=1, K2=0, K3=1, K4=0, K5=0). The formula is 256 × [(K1 × bandwidth + (K3 × delay)] , where bandwidth is the minimum along the path (in tens of Gbps) and delay is cumulative (in tens of microseconds). A path through a 1 Gbps link (bandwidth 10,000,000) and 100 µs delay has metric 256 × [(10⁷ / 10⁶) + (100 / 10)] = 256 × [10 + 10] = 5120. Manipulating delay with delay tens-of-microseconds under an interface is the preferred method to influence EIGRP path selection without affecting actual link performance.

Feasible Successor and Feasibility Condition

A route qualifies as a feasible successor if its reported distance (the neighbor's metric to the destination) is less than the local router's feasible distance (the current best metric). This inequality is the feasibility condition, DUAL's loop-prevention rule. For example, if Router A's best path to 10.2.2.0/24 has feasible distance 5120 via Router B, and Router C advertises the same prefix with reported distance 4096, Router C's path is a feasible successor because 4096 < 5120. Router A stores both paths in the topology table; if Router B fails, Router A immediately uses Router C's path without querying.

In our HSR Layout lab, we configure three-router EIGRP topologies and use show ip eigrp topology to display successors and feasible successors. Students then shut down the successor's interface and observe sub-second failover in debug ip routing logs. This hands-on exercise clarifies why EIGRP is preferred in latency-sensitive environments like VoIP campus networks at Cisco India, where OSPF's SPF recalculation delay (even with incremental SPF) introduces perceptible jitter.

Basic EIGRP Configuration

Enable EIGRP with an autonomous system (AS) number that must match on all routers in the same EIGRP domain:

Router(config)# router eigrp 100
Router(config-router)# network 10.0.0.0
Router(config-router)# network 192.168.1.0 0.0.0.255

The network command uses classful boundaries by default (10.0.0.0 matches all 10.x.x.x addresses) unless you append a wildcard mask. Disable auto-summarization to advertise subnets precisely:

Router(config-router)# no auto-summary

Configure passive interfaces to prevent EIGRP Hello packets on user-facing ports:

Router(config-router)# passive-interface GigabitEthernet0/1

Verify EIGRP neighbors with show ip eigrp neighbors, topology with show ip eigrp topology, and routes with show ip route eigrp. EIGRP routes appear with code D (internal) or D EX (external, redistributed). Adjust K-values only if you have a specific traffic-engineering requirement and ensure all routers in the AS use identical K-values, or they will not form neighbors.

Common Pitfalls and CCIE Interview Gotchas

CCNA candidates frequently misconfigure wildcard masks in OSPF network statements, forgetting that 0.0.0.255 is the inverse of 255.255.255.0. A wildcard mask of 255.255.255.0 would match nothing, causing OSPF to ignore the interface. Another pitfall: configuring OSPF on a router without setting a router ID (manually via router-id or implicitly via highest loopback/physical IP) can cause unpredictable DR elections and adjacency flaps when interfaces bounce.

In EIGRP, mismatched AS numbers prevent neighbor formation, yet the routers silently ignore each other's Hellos—no error message appears. Students waste hours troubleshooting connectivity when the fix is simply router eigrp 100 on both sides. Another gotcha: EIGRP's default auto-summary behavior (disabled in IOS 15.0+ but enabled in older images) summarizes routes at classful boundaries, creating black holes when discontiguous subnets exist. Always verify with show ip protocols that auto-summary is off.

Floating static routes fail if the primary route's AD is manually lowered. For example, if you configure ip route 10.1.1.0 255.255.255.0 10.2.2.2 90 intending it as a backup to EIGRP (AD 90), both routes have AD 90, and the router installs both, load-balancing traffic. The floating static must have AD > 90, such as 91 or 95. Our CCNA course in Bangalore includes a troubleshooting module where students diagnose these exact scenarios using show ip route and show ip protocols, mirroring the diagnostic questions Cisco India interviewers ask in L2 network engineer screenings.

What CCIE Interviewers Probe

Dual CCIE Vikas Swami, who interviews candidates for Cisco TAC and Akamai India roles, reports that interviewers test IP connectivity depth by asking: "Explain why OSPF cost on a 10 GigE interface defaults to 1 when reference bandwidth is 100 Mbps—isn't that incorrect?" The correct answer: yes, it is incorrect for modern networks; you must raise reference bandwidth to 10000 or higher and apply it consistently across all OSPF routers. Another favorite: "If two EIGRP neighbors have mismatched K-values, do they form adjacency?" Answer: no, K-values are part of the Hello packet and must match. A third: "Can a floating static route have AD 0?" Answer: no, AD 0 is reserved for directly connected routes and cannot be manually assigned.

Advanced candidates are asked to calculate EIGRP metric by hand given bandwidth and delay values, or to explain why OSPF Type-5 LSAs flooded into a stub area cause adjacency to drop (answer: stub routers reject Type-5 LSAs, so the ABR must not flood them, enforced by the stub flag in Hello packets). These questions separate candidates who memorized commands from those who understand protocol internals—precisely the skill set our 800+ hiring partners (Cisco, HCL, Aryaka, Movate, Barracuda, Wipro, TCS, Infosys, IBM, Accenture) demand when filling ₹4-8 LPA network engineer roles in Bengaluru.

Real-World Deployment Scenarios in Indian Enterprises

Cisco India's Bengaluru RTP (Research and Technology Park) campus runs a three-tier OSPF design: Area 0 in the core (Catalyst 9500 switches), Area 10 for each building distribution block (Catalyst 9300), and Area 20 stub areas for conference-room access switches. Inter-area summarization at ABRs reduces the campus LSDB from 12,000 entries to under 3,000, enabling sub-second convergence even during building-wide power failures. Static default routes point access switches to their distribution-layer ABR, eliminating the need to run OSPF on every access port.

Aryaka Networks, an SD-WAN provider with Indian headquarters in Bengaluru, uses EIGRP between SD-WAN edge appliances and customer routers because EIGRP's feasible successors enable instant failover when an MPLS link degrades. Aryaka's QuickConnect appliances inject a default route via EIGRP (AD 90) and a floating static default via the appliance's LTE interface (AD 95), so customer traffic fails over to 4G within 200 ms when the primary WAN link drops. This architecture, which our internship students configure in live Aryaka labs, demonstrates how static and dynamic routing coexist in production.

Akamai India's CDN edge nodes in Mumbai and Chennai use static routes to peer with ISP BGP routers, avoiding the overhead of running OSPF or EIGRP on high-throughput 100 GigE links. Each edge node has a static default route to the ISP gateway and static /32 host routes for Akamai's anycast IPs, ensuring deterministic forwarding without protocol churn. Our 4-month paid internship places students at Akamai's Network Operations Center, where they monitor route tables using show ip route summary and respond to static-route misconfigurations that cause cache-miss spikes.

How IP Connectivity Maps to CCNA, CCNP, and CCIE Syllabi

The CCNA 200-301 IP Connectivity domain (25% weight) covers static routes, default routes, floating static routes, OSPF single-area configuration, and EIGRP basic operation. Exam objectives 3.1-3.4 require candidates to configure and verify IPv4/IPv6 static routing, describe OSPF neighbor adjacency, and interpret EIGRP topology tables. Candidates must also explain administrative distance, metric types (cost, hop count, composite), and route selection logic. Our CCNA study guide aligns every lab to these objectives, and students access NHPREP.COM mock tests free for 12 months to drill these concepts until they achieve 90%+ pass rates.

CCNP Enterprise (ENCOR 350-401 and ENARSI 300-410) expands IP connectivity to OSPF multi-area design, EIGRP named mode, route redistribution, policy-based routing, and advanced troubleshooting. ENCOR dedicates 20% to Layer 3 technologies, including OSPFv3, EIGRP for IPv6, and VRF-Lite. ENARSI focuses on redistribution between OSPF/EIGRP/BGP, route filtering with distribute-lists and prefix-lists, and troubleshooting suboptimal routing. Students in our CCNP batch spend four weeks in the HSR Layout lab configuring multi-protocol topologies and using debug ip routing, debug ip ospf adj, and debug eigrp packets to diagnose convergence issues.

CCIE Enterprise Infrastructure v1.1 (written 350-401, lab 8-hour practical) tests IP connectivity at expert level: candidates must design OSPF stub/NSSA areas, optimize EIGRP summarization to minimize query scope, configure route redistribution with metric manipulation, and troubleshoot black holes caused by incorrect summarization or filtering. The lab exam includes scenarios where OSPF and EIGRP coexist, requiring mutual redistribution and careful AD tuning to prevent routing loops. Vikas Swami's Dual CCIE #22239 credentials (Security + Routing & Switching) inform our advanced labs, where students configure the same multi-vendor topologies (Cisco + Juniper + Arista) that appear in CCIE lab sections.

Frequently Asked Questions

What is the difference between a static route and a default route?

A static route specifies a next-hop or exit interface for a particular destination network (e.g., 192.168.10.0/24), while a default route (0.0.0.0/0) matches any destination not explicitly in the routing table. Default routes are a special case of static routes, used primarily on stub routers and internet edge routers to forward all unknown traffic toward an upstream gateway. Both are configured with the ip route command; the default route uses 0.0.0.0 0.0.0.0 as the destination.

Why does EIGRP converge faster than OSPF?

EIGRP maintains a topology table with pre-computed backup paths (feasible successors). When the primary path fails, EIGRP installs the feasible successor instantly without querying neighbors, achieving sub-second convergence. OSPF must detect the failure via dead-interval expiration (default 40 seconds on broadcast networks, tunable to 1 second), flood a new LSA, and re-run Dijkstra's algorithm across the entire area. Even with optimized timers and incremental SPF, OSPF convergence typically takes 1-5 seconds, slower than EIGRP's 200 ms failover when a feasible successor exists.

Can I run OSPF and EIGRP on the same router?

Yes, a single router can run multiple routing protocols simultaneously, each maintaining its own routing process and topology database. The router installs routes from the protocol with the lowest administrative distance: EIGRP (AD 90) beats OSPF (AD 110), so if both advertise the same prefix, the EIGRP route appears in the routing table. To exchange routes between protocols, configure route redistribution under each routing process, specifying metric translation and optional filtering. Redistribution is a CCNP-level topic, common in enterprise networks where OSPF runs in the data center and EIGRP in the campus.

What happens if I configure a static route with the wrong next-hop IP?

If the next-hop IP is unreachable (not in the routing table or not directly connected), the static route remains in the configuration but does not install in the routing table. Use show ip route static to verify installation. If the next-hop is reachable but incorrect (e.g., points to a host that does not forward packets), traffic is black-holed: the router forwards packets to the wrong next-hop, which silently drops them. Always verify static routes with ping and traceroute after configuration.

How do I configure a floating static route for automatic failover?

Append an administrative distance higher than the primary protocol's AD to the ip route command. For example, if OSPF (AD 110) is primary, configure the backup static with AD 120:

Router(config)# ip route 10.1.1.0 255.255.255.0 10.2.2.2 120

The static route remains dormant while OSPF is active. When the OSPF route disappears (link failure, neighbor down), the router installs the floating static automatically. To fail back to OSPF when it recovers, no additional configuration is needed—OSPF's lower AD causes the router to prefer it once the route reappears.

Why do OSPF neighbors stick in 2-Way state and not reach Full?

On broadcast and NBMA networks, OSPF routers elect a Designated Router (DR) and Backup Designated Router (BDR). Only DR and BDR form Full adjacencies with all routers; other routers (DROthers) remain in 2-Way with each other, which is normal and expected. If a router should become DR or BDR but sticks in 2-Way, check priority (default 1; priority 0 cannot become DR) and router ID (highest wins). On point-to-point links, all neighbors must reach Full; 2-Way indicates a problem, often mismatched OSPF network types (ip ospf network point-to-point vs. broadcast).

What is the EIGRP feasibility condition and why does it matter?

The feasibility condition states that a route qualifies as a feasible successor if its reported distance (neighbor's metric) is less than the local router's feasible distance (current best metric). This rule guarantees loop-free backup paths. If a neighbor's reported distance is greater than or equal to the feasible distance, DUAL cannot prove the path is loop-free, so the route is not stored as a feasible successor. When the primary path fails and no feasible successor exists, the router enters Active state and queries all neighbors, delaying convergence. Proper network design—ensuring multiple low-metric paths—maximizes feasible successors and minimizes query scope.

How does administrative distance affect route selection when OSPF and a static route advertise the same prefix?

The router compares administrative distance first, before examining metric. Static routes default to AD 1, OSPF to AD 110. If both advertise 172.16.0.0/16, the static route wins because 1 < 110, and the OSPF route does not install in the routing table. To prefer OSPF, either remove the static route or configure it as a floating static with AD > 110 (e.g., ip route 172.16.0.0 255.255.0.0 10.1.1.1 120). Administrative distance is locally significant and does not propagate to other routers.