Exam Objective 3.2: Troubleshoot IPv4 and IPv6 static routing.
3.2.a Default route
3.2.b Network route
3.2.c Host route
3.2.d Floating static
Static routing is the simplest possible way to tell a router how to reach a destination — an administrator manually types the path rather than relying on a dynamic routing protocol to discover it. Static routes remain heavily used in real networks (stub networks, backup paths, simple topologies, default routes toward an ISP) and are a foundational building block the exam expects you to configure and troubleshoot fluently in both IPv4 and IPv6, across four distinct static route types: default, network, host, and floating.
A static route is a manually configured routing table entry, defined by an administrator rather than learned dynamically. Static routes are simple, predictable, and consume no CPU/bandwidth for ongoing protocol exchanges, but they do not automatically adapt if the network topology changes — if the configured next hop or exit interface becomes unreachable, the static route simply goes down with it (unless a floating static backup is also configured).
Basic IPv4 static route syntax:
ip route [destination-network] [subnet-mask] [next-hop-address or exit-interface] [administrative-distance] [permanent]
Basic IPv6 static route syntax:
ipv6 route [destination-prefix/prefix-length] [next-hop-address or exit-interface] [administrative-distance]
Specifying the next hop — three ways:
Next-hop IP address — ip route 192.168.30.0 255.255.255.0 10.1.1.2 — points to the neighboring router's IP address; the router must then perform a recursive lookup to determine which local exit interface actually reaches that next-hop address
Exit interface — ip route 192.168.30.0 255.255.255.0 GigabitEthernet0/1 — points directly to the router's own local outbound interface, avoiding the need for a recursive lookup, but only valid on point-to-point interface types; using an exit interface on a multi-access (broadcast) interface can trigger unnecessary/incorrect ARP behavior and is generally discouraged
Both next-hop IP and exit interface together — ip route 192.168.30.0 255.255.255.0 GigabitEthernet0/1 10.1.1.2 — the most explicit and generally recommended form, avoiding recursive lookup while still fully specifying the actual next-hop address
Exam Alert: Know that specifying only an exit interface (rather than a next-hop IP) on a multi-access interface like Ethernet is a common misconfiguration that can cause unexpected behavior; specifying only a next-hop IP address is the more universally safe approach, though combining both is best practice on point-to-point-capable configurations.
A default route (0.0.0.0/0 in IPv4, ::/0 in IPv6) matches any destination not more specifically covered by another entry in the routing table, acting as a catch-all path — commonly used for the single exit point out of a stub network toward an ISP or the rest of a larger network.
IPv4 configuration:
ip route 0.0.0.0 0.0.0.0 203.0.113.1
IPv6 configuration:
ipv6 route ::/0 2001:db8:1::1
Verification: show ip route (IPv4) or show ipv6 route (IPv6) will display a line identifying the "Gateway of last resort," directly pointing to the currently active default route, as covered in objective 3.1.
Common default route problems:
The default route's next-hop address is unreachable (down interface, wrong IP, upstream device failure) — traffic destined for any network without a more specific match silently fails
No default route configured at all, and no dynamic routing protocol supplying one either — any destination without a specific matching route is simply dropped
A more specific route unintentionally overriding the intended path — remember from objective 3.1 that longest prefix match always wins, so even a correctly configured default route will be bypassed for any destination that also matches a more specific (but possibly broken or misconfigured) entry
Exam Alert: A default route is the least specific possible route (/0) and is therefore always the last resort — it is only ever used when literally no other more specific entry matches the destination.
A network route (sometimes just called a standard static route) points to an entire destination subnet — the most common and general-purpose type of static route, used when a router needs to reach a specific remote network that isn't learned dynamically.
IPv4 configuration example:
ip route 192.168.50.0 255.255.255.0 10.1.1.2
IPv6 configuration example:
ipv6 route 2001:db8:50::/64 2001:db8:1::2
Typical use cases:
A stub network with only one path in and out, where running a full dynamic routing protocol would be unnecessary overhead
Explicitly defining reachability to a specific remote subnet through a specific next hop, in a small or simply structured topology
Backup or supplemental routes alongside a dynamic routing protocol, for networks the protocol doesn't otherwise learn
Common network route problems:
Wrong subnet or mask specified, so the route doesn't actually match the intended destination traffic at all
Correct destination but wrong/unreachable next-hop address, so the route exists in configuration but never becomes active (won't appear as a valid entry in show ip route if the next hop can't be resolved)
The route is configured but a more specific or lower-AD competing route (from a dynamic protocol, for example) is actually being preferred instead — remember longest prefix match and then AD decide which route wins, per objective 3.1
Exam Alert: A static route only becomes active in the routing table if its specified next hop is actually reachable — a static route pointing to a next hop that itself has no valid path will not appear in show ip route at all, even though the configuration line still exists in show running-config. This distinction (configured vs. actually installed/active) is a frequently tested troubleshooting point.
A host route is a static route to a single specific destination IP address, using a /32 mask in IPv4 (or /128 in IPv6) — the most specific possible route, matching exactly one address and nothing else.
IPv4 configuration example:
ip route 192.168.50.100 255.255.255.255 10.1.1.2
IPv6 configuration example:
ipv6 route 2001:db8:50::100/128 2001:db8:1::2
Typical use cases:
Directing traffic to one specific server or device via a particular path, distinct from how the rest of that device's subnet is routed
Policy-based routing scenarios where a single host's traffic needs special handling (a different next hop, a backup path) separate from its neighbors on the same subnet
Automatically created local host routes — recall from objective 3.1 that every connected interface automatically generates an "L" (local) /32 host route for the router's own interface address, distinct from a manually configured static host route to a remote device
Because a /32 (or /128) is the most specific prefix length possible, a host route will always win longest prefix match against any less specific route to the same address, regardless of administrative distance or metric — this makes host routes a powerful (if narrow) tool for directing one specific address's traffic differently than the rest of its subnet.
Exam Alert: Recognize /32 as always signaling a host route in IPv4 (and /128 in IPv6), and remember that because it's the longest possible prefix, it always takes precedence over any broader matching route for that exact address, no matter what routing source installed the broader route.
A floating static route is a backup static route configured with a deliberately higher administrative distance than the primary route it's meant to back up, so that it remains inactive (not installed in the routing table) as long as the primary route is available, but automatically becomes active if the primary route fails.
How it works: Since only the lowest-AD route to a given destination is actually installed in the active routing table, a floating static route configured with an AD higher than the primary route (whether that primary is a dynamic routing protocol route or another static route) simply sits unused in the background. If the primary route disappears from the table (its next hop becomes unreachable, an interface goes down, or a dynamic protocol loses the route), the floating static route — now the best remaining option — is automatically installed and used instead, without any manual intervention.
Configuration example — primary route via OSPF (AD 110), floating static backup:
ip route 192.168.60.0 255.255.255.0 10.1.1.2 130
The trailing 130 explicitly sets this static route's administrative distance to 130 — higher than OSPF's default 110, ensuring the OSPF-learned route is preferred whenever it's available, while this static route waits in reserve.
Choosing the right AD for a floating static route: The floating static's AD must be set higher than whatever primary route it's meant to back up, but Cisco IOS still needs the value to be lower than 255 (which effectively means "never install/unreachable"). Common practice is to set it comfortably above the primary route's AD (for example, several points above OSPF's 110, or above EIGRP's 90) while leaving meaningful room in case additional backup layers are needed later.
Verification: A floating static route configured correctly will not appear in show ip route at all while the primary route is active and healthy — this is expected, correct behavior, not a misconfiguration. It will only appear once the primary route is withdrawn. To confirm a floating static is correctly configured even while inactive, check show running-config (where it will always be listed) rather than show ip route.
Common floating static route problems:
AD set too low (lower than or equal to the primary route's AD), causing the floating static to incorrectly compete with or even override the intended primary path
AD set to exactly 255, which Cisco IOS treats as unreachable/never-install, meaning the floating static route will never actually be used even as an intended backup
The floating static route's own next hop is also unreachable when failover occurs, meaning even after the primary route fails, the backup route itself can't actually install either — leaving no working path at all
Testing/verification confusion — an administrator seeing no floating static entry in show ip route may incorrectly assume it's broken, when in fact its absence from the active table (while the primary route is healthy) is the entire point and proof that it's working exactly as designed
Exam Alert: The defining, most frequently tested fact about floating static routes is that they are intentionally configured with a higher administrative distance than the primary path, and that not seeing them in show ip route during normal operation is expected and correct — only show running-config reliably confirms a floating static route's configuration regardless of whether it's currently active.
The overall concepts (default, network, host, floating static) apply identically to IPv6, but a few IPv6-specific details matter:
IPv6 requires unicast routing to be explicitly enabled globally before the router will route IPv6 traffic between interfaces at all, similar in spirit to the ip routing requirement for SVIs covered in objective 2.1:
ipv6 unicast-routing
Link-local next hops: Because every IPv6-enabled interface always has a link-local address (covered in objective 1.4), it's possible (and common) to specify a link-local address as the next hop in a static route — but since link-local addresses aren't globally unique, IOS requires the exit interface to also be specified whenever a link-local next-hop address is used, since the router otherwise has no way to know which local interface's link that address applies to:
ipv6 route 2001:db8:50::/64 GigabitEthernet0/1 fe80::2
IPv6 host routes use /128 instead of IPv4's /32, following the same "most specific possible prefix" logic covered above.
Exam Alert: Forgetting ipv6 unicast-routing is a very commonly tested "gotcha" — an administrator can configure IPv6 addresses and static routes perfectly correctly, but without this global command enabled, the router simply will not forward IPv6 traffic between interfaces at all. Also remember that a link-local next hop requires the exit interface to be specified alongside it.
show ip route static / show ipv6 route static — filters the routing table to display only statically configured routes, useful for quickly auditing static configuration without wading through dynamically learned entries
show running-config | include ip route (or ipv6 route) — displays every static route line actually configured, regardless of whether it's currently active/installed, essential for confirming a floating static route's configuration even when it's correctly absent from the active table
ping / traceroute (or their IPv6 equivalents) — confirm actual reachability along the path a static route claims to provide
show ip route [destination] — displays the specific routing table entry (if any) that will actually be used for a given destination, useful for confirming exactly which route — static, dynamic, more specific, or less specific — is winning for that address
Confirm the static route is actually configured as intended with show running-config, checking destination network/mask (or prefix/prefix-length for IPv6), and next-hop specification.
Confirm whether the route actually appears as active/installed in show ip route (or show ipv6 route) — if a network/host static route is missing from the active table, its next hop is likely unreachable.
For IPv6 specifically, confirm ipv6 unicast-routing is enabled globally, and that any link-local next hop also has its exit interface specified.
If the route is meant to be a floating static backup, confirm its administrative distance is set correctly (higher than the primary path, but not 255), and remember that its absence from show ip route while the primary is healthy is expected, correct behavior — verify its configuration via show running-config instead.
If a more specific route is unexpectedly overriding an intended static route (or vice versa), apply longest prefix match logic from objective 3.1 to determine which entry the router will actually select.
Test actual reachability with ping/traceroute along the path the static route is meant to provide, to confirm the configuration produces working end-to-end connectivity, not just a correctly formatted routing table entry.
Q1. Which static route configuration correctly represents a default route in IPv4?
A. ip route 255.255.255.255 0.0.0.0 10.1.1.1
B. ip route 0.0.0.0 0.0.0.0 10.1.1.1
C. ip route 0.0.0.0 255.255.255.255 10.1.1.1
D. ip route 10.1.1.1 0.0.0.0 0.0.0.0
Answer: B. A default route uses the destination network 0.0.0.0 with a mask of 0.0.0.0, representing a route that matches any destination address (equivalent to /0), making it a catch-all path used only when no more specific route matches.
Q2. An administrator configures a floating static route with an administrative distance of 130 as a backup to a primary OSPF route (AD 110). After configuring it, the administrator checks show ip route and does not see the floating static route listed. What does this indicate?
A. The floating static route is misconfigured and not working
B. The floating static route is working exactly as intended, since it only appears once the primary OSPF route is no longer available
C. The administrative distance must be set lower than 110 for the route to appear
D. IPv6 unicast routing has not been enabled
Answer: B. A floating static route is deliberately configured with a higher administrative distance than the primary route it backs up, meaning it will not be installed into the active routing table (and therefore won't appear in show ip route) as long as the primary, lower-AD route remains available. Its absence during normal operation is expected and correct — it only becomes active if the primary route fails.
Q3. Which prefix length always identifies a host route in IPv4?
A. /24
B. /30
C. /32
D. /0
Answer: C. A /32 mask matches exactly one specific IP address and nothing else, making it the most specific possible prefix length and the defining characteristic of a host route in IPv4. The IPv6 equivalent is /128.
Q4. A router has both a static network route to 192.168.50.0/24 and an OSPF-learned route to the more specific 192.168.50.128/25. Which route will be used for a packet destined to 192.168.50.200?
A. The static route, because static routes always have a lower administrative distance
B. The OSPF route, because 192.168.50.128/25 is the more specific (longest prefix) match
C. Both routes will load-balance the traffic equally
D. Neither route will be used since there is a conflict
Answer: B. Longest prefix match is always evaluated before administrative distance. Since 192.168.50.200 falls within the more specific /25 range, the OSPF route wins regardless of its higher administrative distance compared to the static route's default AD of 1.
Q5. An administrator configures IPv6 addresses and a static route on a router, but the router still fails to forward IPv6 traffic between interfaces. What is the most likely missing configuration step?
A. ip routing
B. ipv6 unicast-routing
C. switchport mode trunk
D. spanning-tree portfast
Answer: B. IPv6 requires the global command ipv6 unicast-routing to be enabled before the router will actually route IPv6 traffic between interfaces at all. Addresses and static routes can be configured correctly, but without this command, IPv6 forwarding simply will not occur — this is a distinct requirement from IPv4, which routes by default without an equivalent global enable command.
Q6. An administrator wants to configure an IPv6 static route using a link-local address as the next hop. What additional information must also be specified in the command?
A. The administrative distance, since link-local next hops require a non-default AD
B. The exit interface, since link-local addresses are not globally unique and the router needs to know which local link the address applies to
C. Nothing additional is required; a link-local address alone is always sufficient
D. The destination must also be a link-local address
Answer: B. Because link-local addresses are only unique within their own local link and are reused identically on every IPv6-enabled interface across the network, specifying only a link-local next-hop address leaves the router unable to determine which specific local interface's link that address applies to. The exit interface must be specified alongside the link-local next hop to resolve this ambiguity.