Examkin

IP Connectivity

493 soru

Tüm türler493Çoktan seçmeli250Çoklu seçim113Eşleştirme25Sıralama60Boşluk doldurma22Kısa cevap23
Soru 161Soru →

Complete the Cisco IOS command by entering the missing administrative distance value to configure a floating static route.

Aşağıdaki boşlukları doldurun

An engineer is configuring a backup IPv6 static route to network 2001:db8:40::/64 via next-hop 2001:db8:10::2. The route must remain inactive in the routing table unless the primary OSPFv3 route (administrative distance 110) fails.

Complete the command below by filling in a valid administrative distance value in :

`Router(config)# ipv6 route 2001:db8:40::/64 2001:db8:10::2 `
Cevabı ve açıklamayı göster

Cevap

Any integer from 111 through 254 (for example, 130) that is greater than the OSPFv3 administrative distance of 110.
A floating static route requires an Administrative Distance (AD) higher than the routing protocol it backs up. Since OSPFv3 has a default AD of 110, any integer value between 111 and 254 (such as 120, 130, or 150) placed at the end of the `ipv6 route` command correctly configures the floating static route.

Adım Adım Çözüm

1
Identify the primary route's Administrative Distance (AD).
The primary route uses OSPFv3, which has a default AD of 110.
Floating static routes rely on a higher AD than the active routing protocol so they are only installed when the primary route fails.
2
Determine the valid range for the floating static route AD.
The AD must be strictly greater than 110 and less than 255 (valid Cisco IOS AD range for static routes is 1–254).
An AD of 255 makes a route unroutable/untrustworthy, while an AD of 110 or less would cause the static route to preempt or equal-cost load-share with OSPFv3.
3
Place the AD parameter in the Cisco IOS IPv6 static route syntax.
The syntax is `ipv6 route <prefix/length> <next-hop> [administrative-distance]`.
The final optional position in the command specifies the administrative distance.

Anahtar Kavram

IPv6 Floating Static Route Administrative Distance Configuration
Soru 162Soru →

A network administrator needs to configure a static route on a Cisco router for the destination network 2001:DB8:5::/642001:\text{DB8}:5::/64 using the next-hop router's link-local address FE80::2\text{FE80}::2 reachable via interface GigabitEthernet0/0/1. Which Cisco IOS command correctly configures this route?

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:5::/64 GigabitEthernet0/0/1 fe80::2

Cevap

The command 'ipv6 route 2001:db8:5::/64 GigabitEthernet0/0/1 fe80::2' correctly configures the static route.
The command specifying 'ipv6 route 2001:db8:5::/64 GigabitEthernet0/0/1 fe80::2' follows the correct Cisco IOS syntax. When using a link-local address as a next hop, specifying the local exit interface before the link-local address is mandatory because link-local addresses are ambiguous across multiple physical links.

Adım Adım Çözüm

1
Identify the proper command keyword for IPv6 static routes.
Use 'ipv6 route' rather than 'ip route'.
IPv6 routing configurations require the 'ipv6' keyword prefix in Cisco IOS.
2
Specify destination prefix, local exit interface, and link-local next-hop address in order.
Format as 'ipv6 route 2001:db8:5::/64 GigabitEthernet0/0/1 fe80::2'.
Because link-local addresses (FE80::/10) are reused across multiple interfaces, the router cannot determine which exit interface to use unless specified in the command before the next-hop link-local address.

Anahtar Kavram

IPv6 Static Routing with Link-Local Next-Hop
Soru 163Soru →

A network engineer is optimizing IPv4 static routing on a Cisco IOS router connected to multiple broadcast Ethernet segments. The router currently learns internal prefix 10.10.10.0/24 via OSPFv2 (Administrative Distance 110). Which TWO statements accurately describe the forwarding and configuration behavior of static routes applied to this router? (Select two.)

Geçerli olan tümünü seçin

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Cevap: Configuring 'ip route 10.10.10.0 255.255.255.0 GigabitEthernet0/1 120' creates a floating static route relative to OSPF, but specifying only an Ethernet exit interface forces the router to rely on Proxy ARP from the next-hop device to resolve destination MAC addresses.; Traffic destined to 10.10.10.130 will be forwarded via next-hop 192.168.13.2 when both 'ip route 10.10.10.0 255.255.255.0 192.168.12.2' (AD 1) and 'ip route 10.10.10.128 255.255.255.192 192.168.13.2 130' are in the routing table, because longest prefix match evaluation precedes Administrative Distance comparison.

Cevap

The correct options are the statement regarding Proxy ARP dependency when using an Ethernet exit interface for a floating static route with Administrative Distance 120, and the statement confirming that longest prefix match (/26 over /24) dictates path selection over Administrative Distance during packet forwarding.
The option describing a floating static route with AD 120 is correct because floating backup routes must have a higher AD than the primary protocol (OSPF = 110), and specifying an Ethernet interface without a next-hop IP requires Proxy ARP to discover destination MAC addresses. The option addressing destination 10.10.10.130 is also correct because the router prioritizes the most specific prefix match (/26 over /24) during forwarding lookup regardless of the AD of the installed static routes.

Adım Adım Çözüm

1
Evaluate floating static route behavior and exit interface considerations.
OSPF has a default AD of 110. A static route configured with AD 120 has a higher distance, floating out of the routing table until OSPF fails. On broadcast Ethernet interfaces, omitting the next-hop IP forces ARP queries for individual target IPs, requiring Proxy ARP on adjacent devices.
Floating routes require AD > primary protocol AD. Broadcast interfaces need explicit next-hop IPs to prevent per-destination ARP lookups.
2
Analyze routing decision hierarchy (Longest Prefix Match vs Administrative Distance).
Administrative distance determines which routes are installed into the routing table. Once installed, packet forwarding decisions rely strictly on the Longest Prefix Match (/26 mask matches 10.10.10.130 more specifically than /24).
Prefix length (/26 > /24) takes absolute priority during active packet forwarding lookup.
3
Identify misconceptions in backup static route AD configuration and default route exit interface usage.
Configuring AD 90 makes the static route primary over OSPF (AD 110), failing the floating backup requirement. Pointing a static route (or default route) solely to an Ethernet exit interface causes severe ARP table expansion.
Lower AD wins installation; broadcast interfaces treat all destinations as local when no next-hop IP is provided.

Anahtar Kavram

IPv4 Static Route Selection, Administrative Distance, and Exit Interface Dynamics
Tahmini Süre:3m 0s
Soru 164Soru →

Refer to the following partial output from the `show ip route` command on a Cisco router:

text
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

S* 0.0.0.0/0 [1/0] via 10.0.0.1, GigabitEthernet0/0
S 172.20.0.0/16 [1/0] via 10.1.1.1, GigabitEthernet0/1
O 172.20.12.0/24 [110/30] via 10.2.2.2, GigabitEthernet0/2
D 172.20.12.64/27 [90/3072] via 10.3.3.3, GigabitEthernet0/3
S 172.20.12.64/30 [1/0] via 10.4.4.4, GigabitEthernet0/4

The router receives an IP packet destined for 172.20.12.70172.20.12.70. Which TWO statements correctly describe how the router processes and forwards this packet?

Geçerli olan tümünü seçin

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Cevap: The router forwards the packet out interface GigabitEthernet0/3 toward next-hop IP 10.3.3.3.; The route 172.20.12.64/27 is selected over 172.20.0.0/16 because Longest Prefix Match takes precedence over Administrative Distance.

Cevap

The router forwards the packet out interface GigabitEthernet0/3 toward next-hop IP 10.3.3.3, and the route 172.20.12.64/27 is selected over 172.20.0.0/16 because Longest Prefix Match takes precedence over Administrative Distance.
When a router receives a packet, it compares the destination IP address against all entries in its routing table. The matching route with the longest prefix length (most specific mask) is selected. Here, 172.20.12.70 matches 0.0.0.0/0 (/0), 172.20.0.0/16 (/16), 172.20.12.0/24 (/24), and 172.20.12.64/27 (/27). The /27 route is the longest match, so traffic is sent via next-hop 10.3.3.3 out GigabitEthernet0/3. Administrative Distance is ignored because prefix lengths differ.

Adım Adım Çözüm

1
Determine subnet boundaries for all matching route entries against destination IP 172.20.12.70
0.0.0.0/0 matches (/0); 172.20.0.0/16 matches (/16); 172.20.12.0/24 matches (/24); 172.20.12.64/27 covers 172.20.12.64 - 172.20.12.95 and matches (/27); 172.20.12.64/30 covers 172.20.12.64 - 172.20.12.67 and DOES NOT match.
Only routes whose network range actually encompasses the destination IP address can be considered for packet forwarding.
2
Compare prefix lengths among all valid candidate matching routes
Candidate prefix lengths are /0, /16, /24, and /27. The longest prefix match is 172.20.12.64/27.
Cisco forwarding decision logic strictly prefers the route with the most specific (longest) subnet mask regardless of routing protocol origin or Administrative Distance.
3
Identify the egress interface and next-hop address for the winning route 172.20.12.64/27
Next-hop IP is 10.3.3.3 via egress interface GigabitEthernet0/3.
The routing table entry `D 172.20.12.64/27 [90/3072] via 10.3.3.3, GigabitEthernet0/3` directly specifies these parameters.

Anahtar Kavram

Router Forwarding Decision Logic and Longest Prefix Match (LPM) Precedence
Soru 165Soru →

An administrator executes the `show ip route` command on a Cisco router and receives the following partial routing table output:

text
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

Gateway of last resort is 10.5.5.5 to network 0.0.0.0

S 172.16.0.0/16 [1/0] via 10.1.1.1, GigabitEthernet0/0
D 172.16.24.0/22 [90/2170112] via 10.2.2.2, GigabitEthernet0/1
O 172.16.25.0/25 [110/20] via 10.3.3.3, GigabitEthernet0/2
D 172.16.25.96/28 [90/307200] via 10.4.4.4, GigabitEthernet0/3
S* 0.0.0.0/0 [1/0] via 10.5.5.5, GigabitEthernet0/4

When a frame containing an IPv4 packet destined for 172.16.25.100172.16.25.100 arrives at this router, which next-hop IP address and egress interface will be selected to forward the packet?

Cevabı ve açıklamayı göster

Cevap: 10.4.4.4 via GigabitEthernet0/3

Cevap

10.4.4.4 via GigabitEthernet0/3
When a router makes a forwarding decision, it evaluates all matching entries in the routing table according to the Longest Prefix Match rule. Subnet 172.16.25.96/28 covers IP addresses from 172.16.25.96 to 172.16.25.111, including 172.16.25.100. Because /28 is the longest (most specific) prefix matching this destination, the router selects next-hop 10.4.4.4 via GigabitEthernet0/3 regardless of lower administrative distances on less specific routes.

Adım Adım Çözüm

1
Identify all candidate routes matching destination IP 172.16.25.100172.16.25.100
Candidate routes are 172.16.0.0/16, 172.16.24.0/22, 172.16.25.0/25, 172.16.25.96/28, and default route 0.0.0.0/0.
Before comparing administrative distance or metrics, the router finds all routing table entries that cover the destination address.
2
Determine the host range of the subnet 172.16.25.96/28
The subnet range for 172.16.25.96/28 spans from 172.16.25.96 to 172.16.25.111.
A prefix length of /28 yields a block size of 2(32−28)=162^{(32-28)} = 16 IP addresses. Destination 172.16.25.100172.16.25.100 falls within 172.16.25.96−172.16.25.111172.16.25.96 - 172.16.25.111.
3
Apply the Longest Prefix Match (LPM) rule
Compare subnet mask lengths: /28 > /25 > /22 > /16 > /0. The route for 172.16.25.96/28 has the longest prefix match.
Longest prefix match is the primary criterion in router forwarding logic, overriding Administrative Distance and routing protocol metrics.
4
Determine next-hop IP and egress interface
Next-hop 10.4.4.4 via GigabitEthernet0/3.
The matching /28 entry specifies next-hop IP 10.4.4.4 out interface GigabitEthernet0/3.

Anahtar Kavram

Longest Prefix Match (LPM) Rule in Forwarding Logic
Tahmini Süre:2m 0s
Soru 166Soru →

Refer to the following routing table output from a Cisco router:

text
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

S* 0.0.0.0/0 [1/0] via 10.0.0.1
S 192.168.0.0/16 [1/0] via 10.1.1.1
O 192.168.10.0/24 [110/20] via 10.2.2.2, 00:05:12, GigabitEthernet0/1
D 192.168.10.32/28 [90/2170112] via 10.3.3.3, 00:12:45, GigabitEthernet0/2

When a packet destined for 192.168.10.45192.168.10.45 arrives at the router, which next-hop IP address will be selected to forward the packet?

Cevabı ve açıklamayı göster

Cevap: 10.3.3.3

Cevap

10.3.3.3
When forwarding an IP packet, a router first checks all entries in its routing table to find routes that match the destination IP address. If multiple matching routes exist, the router always selects the route with the longest prefix mask (most specific match). The destination 192.168.10.45 falls into the range 192.168.10.32 through 192.168.10.47 provided by the /28 route. Because /28 is longer than /24, /16, and /0, the next-hop IP 10.3.3.3 is chosen.

Adım Adım Çözüm

1
Identify all matching routes for destination IP 192.168.10.45
Matching routes are 0.0.0.0/0, 192.168.0.0/16, 192.168.10.0/24, and 192.168.10.32/28.
The destination IP address falls within the network range of all four route entries.
2
Apply the Longest Prefix Match (LPM) rule to compare prefix lengths
Prefix lengths are /0, /16, /24, and /28. The /28 prefix is the longest (most specific).
Routers always evaluate prefix length first before comparing Administrative Distance or Metric.
3
Determine the next-hop IP associated with the longest prefix match route
The route 192.168.10.32/28 specifies next-hop IP 10.3.3.3.
The packet is forwarded to the next-hop IP associated with the winning prefix route.

Anahtar Kavram

Longest Prefix Match (LPM) rule in router forwarding decision logic
Soru 167Soru →

Refer to the following routing table snippet from a Cisco router:

text
Codes: C - connected, S - static, R - RIP, B - BGP, O - OSPF, D - EIGRP
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

D 172.16.0.0/16 [90/2172416] via 10.10.10.2, GigabitEthernet0/0/1
O 172.16.32.0/19 [110/30] via 10.20.20.2, GigabitEthernet0/0/2
S 172.16.32.0/21 [1/0] via 10.30.30.2, GigabitEthernet0/0/3
O 172.16.36.0/24 [110/10] via 10.40.40.2, GigabitEthernet0/0/4
S* 0.0.0.0/0 [1/0] via 10.0.0.1, GigabitEthernet0/0/0

Which two statements correctly describe how the router forwards traffic based on this routing table? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: A packet destined for 172.16.36.50 is forwarded out GigabitEthernet0/0/4 because 172.16.36.0/24 provides the longest prefix match.; A packet destined for 172.16.40.1 is forwarded out GigabitEthernet0/0/2 because 172.16.32.0/19 is a more specific match than 172.16.0.0/16.

Cevap

The router forwards traffic destined for 172.16.36.50 out GigabitEthernet0/0/4 based on the /24 longest prefix match, and forwards traffic destined for 172.16.40.1 out GigabitEthernet0/0/2 based on the /19 longest prefix match.
When a router performs a destination lookup, it selects the route with the most specific match (longest prefix length, or highest subnet mask number). The administrative distance and routing metric are ignored during this lookup phase because the candidate routes represent different destination network ranges. Therefore, 172.16.36.50 matches the /24 route out GigabitEthernet0/0/4, while 172.16.40.1 falls within the 172.16.32.0/19 subnet (range 172.16.32.0 to 172.16.63.255) and matches /19 over /16.

Adım Adım Çözüm

1
Evaluate subnet membership for destination 172.16.36.50.
Matches 172.16.0.0/16, 172.16.32.0/19, 172.16.32.0/21, and 172.16.36.0/24.
Determining all eligible route entries in the routing table for the destination IP.
2
Apply the Longest Prefix Match rule to selection for 172.16.36.50.
Select 172.16.36.0/24 (via 10.40.40.2 on GigabitEthernet0/0/4).
Prefix length /24 has the most matching high-order bits (24 bits), overriding Administrative Distance.
3
Evaluate subnet membership for destination 172.16.40.1.
Matches 172.16.0.0/16 and 172.16.32.0/19 (range 172.16.32.0 to 172.16.63.255). Does not match 172.16.32.0/21 (range 172.16.32.0 to 172.16.39.255) or 172.16.36.0/24.
Calculating subnet boundary limits for /19 and /21.
4
Apply the Longest Prefix Match rule to selection for 172.16.40.1.
Select 172.16.32.0/19 (via 10.20.20.2 on GigabitEthernet0/0/2).
/19 is a longer prefix match than /16.

Anahtar Kavram

Router Forwarding Decision Logic (Longest Prefix Match Rule)
Tahmini Süre:2m 0s
Soru 168Soru →

Refer to the following partial IPv4 routing table output from a Cisco router:

Codes: C - connected, S - static, O - OSPF, D - EIGRP

Gateway of last resort is not set

172.16.0.0/16 is subnetted, 3 subnets
S 172.16.0.0/16 [1/0] via 10.1.1.1
O 172.16.32.0/24 [110/20] via 10.2.2.2
D 172.16.32.32/27 [90/307200] via 10.3.3.3

If the router receives an IP packet destined for 172.16.32.45172.16.32.45, to which next-hop IP address will the packet be forwarded?

Cevabı ve açıklamayı göster

Cevap: 10.3.3.3

Cevap

The router will forward the packet to next-hop IP address 10.3.3.3 because 172.16.32.32/27 is the longest matching prefix for destination IP 172.16.32.45.
When a router performs a forwarding lookup for destination IP address 172.16.32.45, it checks all matching entries in its routing table. The destination address 172.16.32.45 matches 172.16.0.0/16, 172.16.32.0/24, and 172.16.32.32/27 (which covers host IP addresses from 172.16.32.33 through 172.16.32.62). The /27 route matches 27 continuous network bits, which is the longest prefix match compared to /24 or /16. Therefore, the router forwards the packet to 10.3.3.3.

Adım Adım Çözüm

1
Evaluate all routes in the routing table against destination IP 172.16.32.45
Three routes match: 172.16.0.0/16, 172.16.32.0/24, and 172.16.32.32/27 (since range .32 to .63 contains .45).
Routing decision logic requires identifying all candidate routes that encompass the destination IP.
2
Compare subnet mask lengths to determine the Longest Prefix Match (LPM)
The prefix length /27 (27 bits) is greater than /24 (24 bits) and /16 (16 bits).
The router always prefers the most specific route (longest subnet mask / highest number of matching network bits) regardless of Administrative Distance or metric.
3
Identify the next-hop address associated with the longest matching route
The route 172.16.32.32/27 specifies next-hop 10.3.3.3.
Packet forwarding uses the next-hop associated with the route selected by LPM.

Anahtar Kavram

Router Forwarding Decision Logic & Longest Prefix Match (LPM)
Soru 169Soru →

A Cisco router receives an IPv4 packet on an ingress interface that must be forwarded to a remote destination. Place the router forwarding decision and processing steps in the correct chronological order from packet arrival to egress transmission.

Öğeleri doğru sıraya koymak için sürükleyin

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Cevap

The correct sequence of router forwarding decision steps is: 1. Extract the destination IPv4 address from the incoming packet header. 2. Search the routing table for matching entries and select the route with the longest prefix mask. 3. Identify the designated exit interface and next-hop IPv4 address from the winning route entry. 4. Query the ARP cache to resolve the Layer 2 MAC address associated with the next-hop IPv4 address. 5. Decrement the IPv4 Time-to-Live (TTL) value, recalculate the header checksum, and encapsulate the packet into a new Layer 2 frame for egress.
When an IPv4 packet arrives on a router interface, the router first parses the IP header to extract the destination IP address. Next, it consults the routing table to find matching network prefixes, selecting the route entry with the longest prefix mask (most specific match). From this winning entry, the router extracts the designated exit interface and next-hop IP. It then queries its ARP cache to discover the destination MAC address corresponding to that next-hop IP. Finally, the router modifies the IP header by decrementing the TTL and recalculating the checksum, encapsulates the packet in a fresh Layer 2 frame with new source/destination MAC addresses, and transmits it out the exit interface.

Adım Adım Çözüm

1
Packet Ingress and IP Parsing
The router receives the Layer 2 frame, verifies the checksum, and extracts the target IPv4 destination address.
The router cannot perform routing table lookups until the destination IP address is identified.
2
Routing Table Lookup via Longest Prefix Match
The router compares the destination IP against entries in the routing table and selects the prefix with the greatest number of matching subnet bits.
Longest Prefix Match (LPM) is the fundamental rule governing packet forwarding lookup in IP routing tables.
3
Forwarding Information Extraction
The winning route entry reveals the egress interface and the next-hop gateway address.
The next-hop address and exit interface are required to prepare the outgoing data link layer frame.
4
Layer 2 Address Resolution
The router looks up the next-hop IPv4 address in its ARP table to find its corresponding MAC address.
Ethernet encapsulation requires a valid destination MAC address for the next-hop device on the multi-access segment.
5
Header Modification and Egress Encapsulation
The router decrements TTL, updates the IP checksum, wraps the packet in a new Layer 2 frame with local source MAC and next-hop destination MAC, and transmits it.
This completes the Layer 3 forwarding operation and sends the packet toward its final destination.

Anahtar Kavram

Router Forwarding Decision Logic and Packet Lifecycle
Soru 170Soru →

An engineer evaluates an operational Cisco router process handling an incoming packet addressed to target host 172.16.35.45. The active IPv4 routing database displays the following entries:

S 172.16.32.0/20 [1/0] via 10.1.1.1
D 172.16.32.0/21 [90/307200] via 10.3.3.3
O 172.16.35.0/26 [110/65] via 10.2.2.2
B 172.16.0.0/16 [20/0] via 10.4.4.4

Which next-hop IP address will be utilized to transmit this traffic?

Cevabı ve açıklamayı göster

Cevap: 10.2.2.2

Cevap

10.2.2.2 is selected because the OSPF route 172.16.35.0/26 provides the longest prefix match (/26) for the destination IP address 172.16.35.45.
When a router performs a forwarding lookup for a destination IP address (172.16.35.45), it evaluates all matching prefix entries in the IPv4 routing table. In this case, 172.16.35.45 falls into the network ranges of all four listed prefixes (/16, /20, /21, and /26). According to the Longest Prefix Match principle, the router selects the entry with the highest mask length (/26). Therefore, the packet is forwarded to next-hop 10.2.2.2 associated with 172.16.35.0/26.

Adım Adım Çözüm

1
Determine subnet boundaries for all routing table entries relative to destination 172.16.35.45
172.16.0.0/16 covers 172.16.0.0 - 172.16.255.255 (Match length /16).
172.16.32.0/20 covers 172.16.32.0 - 172.16.47.255 (Match length /20).
172.16.32.0/21 covers 172.16.32.0 - 172.16.39.255 (Match length /21).
172.16.35.0/26 covers 172.16.35.0 - 172.16.35.63 (Match length /26).
All four entries contain the destination IP address 172.16.35.45.
2
Apply the Longest Prefix Match (LPM) rule to select the forwarding entry
The route with subnet mask /26 (172.16.35.0/26) has the greatest number of matching network bits (26 bits).
Cisco routers always evaluate the most specific route (longest subnet mask) first during packet forwarding decisions, prior to administrative distance or metric comparisons.
3
Identify the next-hop address associated with the chosen /26 route
The route O 172.16.35.0/26 is reachable via next-hop 10.2.2.2.
The next-hop address specified in the routing table for the /26 network is 10.2.2.2.

Anahtar Kavram

Longest Prefix Match Rule
Tahmini Süre:1m 30s
Soru 171Soru →

A network engineer is configuring a static route on a Cisco router to reach remote network 2001:db8:3c4d:10::/642001:\text{db8}:3\text{c}4\text{d}:10::/64. The adjacent router's interface uses the link-local IPv6 address fe80::1\text{fe80}::1 and is directly attached to local interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}. Which Cisco IOS command correctly establishes this static route?

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:3c4d:10::/64 GigabitEthernet0/0/1 fe80::1

Cevap

The command 'ipv6 route 2001:db8:3c4d:10::/64 GigabitEthernet0/0/1 fe80::1' correctly configures the fully specified static route.
When configuring an IPv6 static route using a link-local next-hop address, Cisco IOS requires a fully specified static route that includes both the local exit interface and the link-local next-hop IPv6 address. This is required because link-local IPv6 addresses are only unique on a single link and could be used on multiple interfaces simultaneously.

Adım Adım Çözüm

1
Identify the target IPv6 static routing command keyword and prefix syntax.
IPv6 static routes must begin with 'ipv6 route' followed by the target destination prefix and prefix length (2001:db8:3c4d:10::/642001:\text{db8}:3\text{c}4\text{d}:10::/64).
Cisco IOS requires the explicit 'ipv6 route' keyword for IPv6 routing entries.
2
Determine the requirement for using link-local next-hop addresses.
Because link-local addresses (FE80::/10) are link-specific and can exist on multiple interfaces of the same router, Cisco IOS cannot resolve the exit interface implicitly.
Specifying both the local interface and the link-local next-hop address (fully specified static route) eliminates exit interface ambiguity.

Anahtar Kavram

IPv6 Fully Specified Static Route with Link-Local Next-Hop
Soru 172Soru →

A network administrator needs to configure an IPv6 static route on a Cisco IOS router for the destination network 2001:db8:acad:10::/642001:\text{db8}:\text{acad}:10::/64. The next-hop router's link-local IPv6 address is fe80::1\text{fe80}::1, and the local exit interface is GigabitEthernet0/0/1. Which Cisco IOS command correctly configures this static route?

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/0/1 fe80::1

Cevap

The command 'ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/0/1 fe80::1' correctly configures the static route.
When pointing an IPv6 static route to a link-local next-hop address, Cisco IOS requires both the outbound exit interface and the next-hop IPv6 address to be specified. The syntax 'ipv6 route <destination-prefix> <exit-interface> <link-local-address>' satisfies this requirement.

Adım Adım Çözüm

1
Identify the destination prefix and mask
The target network is 2001:db8:acad:10::/64.
Static routes in Cisco IOS require the destination network prefix first.
2
Evaluate the requirements for using a link-local next-hop address
Link-local addresses (fe80::/10) are ambiguous because they exist on every interface.
Cisco IOS requires specifying the exit interface along with the link-local next-hop address.
3
Construct the exact Cisco IOS IPv6 static route command syntax
ipv6 route 2001:db8:acad:10::/64 GigabitEthernet0/0/1 fe80::1
The correct format is 'ipv6 route <prefix/length> <exit-interface> <next-hop-address>'.

Anahtar Kavram

IPv6 Static Route Link-Local Next-Hop Configuration
Soru 173Soru →

A network engineer is configuring static routes on a Cisco IOS router to establish reachability to remote networks. Which TWO commands represent syntactically valid IPv6 static route configurations?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:acad:2::/64 gigabitethernet 0/0/0 fe80::1; ipv6 route 2001:db8:acad:3::/64 2001:db8:acad:1::2 130

Cevap

The syntactically valid IPv6 static route configurations are the fully specified route specifying both GigabitEthernet 0/0/0 and next-hop link-local address fe80::1, and the floating static route specifying the global unicast next-hop 2001:db8:acad:1::2 with an administrative distance of 130.
The command specifying both the exit interface GigabitEthernet 0/0/0 and the link-local next-hop address fe80::1 is valid because link-local addresses require an exit interface to define the link scope. The command specifying destination network 2001:db8:acad:3::/64 with global unicast next-hop 2001:db8:acad:1::2 and administrative distance 130 is also valid for configuring a floating static route.

Adım Adım Çözüm

1
Evaluate the link-local next-hop static route syntax requirements.
Link-local addresses (fe80::/10) require an exit interface to be specified because link-local addresses are only unique to a given link.
Cisco IOS cannot resolve an egress interface solely from a link-local next-hop address.
2
Evaluate global unicast static route syntax and administrative distance positioning.
Global unicast next-hop static routes can be configured with an optional administrative distance parameter at the end of the command.
Setting an administrative distance higher than dynamic routing protocols creates a backup or floating static route.

Anahtar Kavram

IPv6 Static Route Syntax Rules for Link-Local and Global Unicast Next Hops
Soru 174Soru →

A Cisco router currently learns the active route to destination network 2001:DB8:ACAD:20::/642001:\text{DB8}:\text{ACAD}:20::/64 via OSPFv3 with an administrative distance of 110. An engineer must configure a backup floating static IPv6 route to this remote network. The backup path uses the next-hop router's link-local IPv6 address FE80::2\text{FE80}::2 through the local interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}. Which command correctly configures this floating static IPv6 route on the Cisco IOS router?

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:acad:20::/64 GigabitEthernet0/0/1 fe80::2 120

Cevap

The command 'ipv6 route 2001:db8:acad:20::/64 GigabitEthernet0/0/1 fe80::2 120' correctly configures the fully specified floating static IPv6 route.
The correct command fully specifies the exit interface alongside the link-local next-hop IPv6 address and sets an administrative distance of 120. In IPv6 static routing, specifying a link-local address as a next hop requires the local exit interface (GigabitEthernet0/0/1). Additionally, configuring an administrative distance greater than OSPFv3's default distance of 110 ensures the static route remains dormant in the routing table until the primary OSPFv3 route fails.

Adım Adım Çözüm

1
Identify the requirements for using a link-local IPv6 address as a static route next hop.
Because link-local addresses (FE80::/10) are ambiguous without a scope, Cisco IOS requires fully specified static routes that include both the local exit interface and the link-local next-hop address.
Without the local interface parameter, the router cannot determine which outgoing interface to send traffic to reach the link-local neighbor.
2
Determine the necessary Administrative Distance (AD) for a floating static route.
The AD must be strictly greater than the AD of the primary routing protocol (OSPFv3 default AD is 110). An AD value of 120 is higher than 110.
A floating static route remains inactive in the routing table until the primary route with a lower administrative distance fails.
3
Assemble the complete Cisco IOS IPv6 static route command syntax.
The correct command format is 'ipv6 route <destination-prefix/mask> <exit-interface> <next-hop-link-local-address> <administrative-distance>'.
This guarantees correct forwarding interface binding and proper floating route administrative distance operation.

Anahtar Kavram

IPv6 Fully Specified Floating Static Route Configuration
Soru 175Soru →

Refer to the following routing table snippet from a Cisco router:

text
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

O 192.168.1.0/24 [110/20] via 10.1.1.1, GigabitEthernet0/0
D 192.168.1.128/26 [90/307200] via 10.2.2.2, GigabitEthernet0/1
S 192.168.1.136/29 [1/0] via 10.3.3.3, GigabitEthernet0/2
S* 0.0.0.0/0 [1/0] via 10.0.0.1, GigabitEthernet0/3

When the router receives an IP packet destined for 192.168.1.138192.168.1.138, which next-hop IP address and exit interface will the router select to forward the packet?

Cevabı ve açıklamayı göster

Cevap: 10.3.3.3 via GigabitEthernet0/2

Cevap

10.3.3.3 via GigabitEthernet0/2
When a router makes a forwarding decision, it evaluates all matching routes in its routing table and selects the one with the longest prefix mask length (most specific route). The destination IP address 192.168.1.138 is contained within 192.168.1.0/24, 192.168.1.128/26, 192.168.1.136/29, and 0.0.0.0/0. Among these matching entries, 192.168.1.136/29 has the longest subnet mask (/29). Therefore, the packet is forwarded to next-hop 10.3.3.3 out of GigabitEthernet0/2.

Adım Adım Çözüm

1
Evaluate all routes in the routing table against destination IP 192.168.1.138192.168.1.138.
Matching routes are 192.168.1.0/24192.168.1.0/24, 192.168.1.128/26192.168.1.128/26 (range 192.168.1.128−192.168.1.191192.168.1.128 - 192.168.1.191), 192.168.1.136/29192.168.1.136/29 (range 192.168.1.136−192.168.1.143192.168.1.136 - 192.168.1.143), and 0.0.0.0/00.0.0.0/0.
The destination address must fall within the subnet range of a candidate route.
2
Apply the Longest Prefix Match (LPM) rule to select the best matching route.
The route 192.168.1.136/29192.168.1.136/29 has a mask length of /29/29, which is longer (more specific) than /26/26, /24/24, and /0/0.
Routers always prioritize the route with the longest matching subnet mask length regardless of Administrative Distance or metric.
3
Identify the next-hop IP and exit interface associated with the chosen LPM route.
The route 192.168.1.136/29192.168.1.136/29 specifies next-hop 10.3.3.310.3.3.3 via interface `GigabitEthernet0/2`.
The forwarding engine uses the egress parameters defined by the winning route entry.

Anahtar Kavram

Longest Prefix Match Rule in Router Forwarding Decisions
Tahmini Süre:1m 0s
Soru 176Soru →

An administrator examines the following output from a Cisco router's IPv4 routing table:

text
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 6 subnets, 3 masks
O 10.20.30.0/24 [110/20] via 192.168.12.2, 00:15:32, GigabitEthernet0/0
D 10.20.30.32/28 [90/307200] via 192.168.23.2, 01:42:10, GigabitEthernet0/1
S 10.20.30.40/29 [1/0] via 192.168.34.2
O IA 10.20.30.44/30 [110/50] via 192.168.45.2, 00:08:19, GigabitEthernet0/2

Which two statements accurately interpret the components and forwarding behavior of this routing table? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: Packets destined for host 10.20.30.45 will be egressed via interface GigabitEthernet0/2 because 10.20.30.44/30 provides the longest matching prefix for that destination address.; The bracketed notation [90/307200] in the 10.20.30.32/28 route entry specifies an Administrative Distance of 90 and an EIGRP composite metric of 307200.

Cevap

The correct statements are that packets for destination 10.20.30.45 will exit via GigabitEthernet0/2 due to longest prefix match (/30), and that [90/307200] defines an Administrative Distance of 90 and metric of 307200.
The router uses the Longest Prefix Match rule during packet lookup. Since destination 10.20.30.45 falls into 10.20.30.44/30 (range 10.20.30.44 to 10.20.30.47), the /30 prefix length is the longest and takes precedence over /29, /28, and /24. Additionally, routing table bracket notation [X/Y] represents [Administrative Distance / Metric], correctly mapping [90/307200] to AD 90 and EIGRP metric 307200.

Adım Adım Çözüm

1
Evaluate subnet range matching for target IP address 10.20.30.45 across all routing table entries.
The target address 10.20.30.45 matches 10.20.30.0/24, 10.20.30.32/28 (32-47), 10.20.30.40/29 (40-47), and 10.20.30.44/30 (44-47).
Before making forwarding decisions, the router determines which routing table prefixes encompass the destination address.
2
Apply the Longest Prefix Match (LPM) rule to select the forwarding route.
Prefix length /30 is more specific than /29, /28, and /24. The route 10.20.30.44/30 is selected.
Routers always prioritize the longest (most specific) network mask when choosing between matching routing entries, regardless of Administrative Distance.
3
Interpret routing table component metrics in the brackets [X/Y].
[90/307200] corresponds to AD=90 (Internal EIGRP) and Metric=307200.
The first number inside the brackets is Administrative Distance (trustworthiness), and the second number is the path metric.

Anahtar Kavram

Routing Table Components and Longest Prefix Match Forwarding Logic
Soru 177Soru →

A network administrator is configuring IPv6 static routing on router R1 to reach network 2001:db8:89ab:10::/642001:\text{db8}:89\text{ab}:10::/64. The directly connected neighbor router interface is configured with global unicast address 2001:db8:1234:1::22001:\text{db8}:1234:1::2 and link-local address fe80::2\text{fe80}::2. Router R1 uses local interface GigabitEthernet0/1 to reach this neighbor. Which TWO Cisco IOS commands represent valid IPv6 static route configurations on R1?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:89ab:10::/64 GigabitEthernet0/1 fe80::2; ipv6 route 2001:db8:89ab:10::/64 2001:db8:1234:1::2

Cevap

The two valid Cisco IOS static route commands are 'ipv6 route 2001:db8:89ab:10::/64 GigabitEthernet0/1 fe80::2' and 'ipv6 route 2001:db8:89ab:10::/64 2001:db8:1234:1::2'.
In Cisco IOS, IPv6 static routes configured with a link-local address as the next hop MUST include the local egress interface (fully specified route). Alternatively, a global unicast next-hop address can be configured directly without an egress interface specified.

Adım Adım Çözüm

1
Identify valid next-hop options for Cisco IOS IPv6 static routes
IPv6 static routes can use a global unicast next-hop address alone, an outbound local interface with a global unicast address, or a fully specified combination of local exit interface and link-local next-hop address.
Link-local addresses have link-local scope and exist on multiple interfaces simultaneously, making the exit interface strictly mandatory when using link-local next hops.
2
Evaluate the option using local exit interface and link-local address
The command specifying GigabitEthernet0/1 alongside link-local address fe80::2 is valid.
It fulfills the mandatory requirement of declaring the local egress interface when referencing link-local IPv6 addresses.
3
Evaluate the option using global unicast next-hop address
The command specifying next-hop global unicast address 2001:db8:1234:1::2 is valid.
Global unicast addresses are globally unique and routable without explicit interface identification.

Anahtar Kavram

IPv6 Static Route Next-Hop Requirements
Soru 178Soru →

A network engineer needs to manually configure a backup route on Router R1 toward the remote prefix 2001:db8:cafe:40::/642001:\text{db8}:\text{cafe}:40::/64. The primary route to this subnet is learned via OSPFv3 with an administrative distance of 110. The engineer must use the neighboring router's link-local address fe80::250:56ff:fe9a:12ab\text{fe80}::250:56ff:\text{fe9a}:12ab reachable through interface GigabitEthernet0/0/1. What complete Cisco IOS global configuration command must be entered to establish this route as a floating static route with an administrative distance of 130?

Aşağıdaki boşlukları doldurun

R1(config)#
Cevabı ve açıklamayı göster

Cevap

The complete command required is 'ipv6 route 2001:db8:cafe:40::/64 GigabitEthernet0/0/1 fe80::250:56ff:fe9a:12ab 130'.
To route IPv6 traffic using a link-local address (FE80::/10) as the next hop, Cisco IOS requires a fully specified static route syntax that defines the local exit interface followed by the link-local address. Without specifying the exit interface, the router cannot determine which local physical or logical link reaches that link-local address. Additionally, appending the administrative distance value 130 ensures the static route remains inactive in the routing table until the primary OSPFv3 route (AD 110) fails.

Adım Adım Çözüm

1
Identify the base global configuration command for IPv6 static routing.
The command structure starts with 'ipv6 route'.
Cisco IOS requires 'ipv6 route' in global configuration mode to declare static routes for IPv6.
2
Append the destination IPv6 prefix and prefix-length.
Add '2001:db8:cafe:40::/64' after the command keyword.
Static routing requires specifying the exact destination prefix using CIDR slash notation.
3
Identify the mandatory parameters when utilizing a link-local address as the next hop.
Specify the local exit interface 'GigabitEthernet0/0/1' immediately followed by the link-local address 'fe80::250:56ff:fe9a:12ab'.
Because link-local addresses (FE80::/10) are only unique on a per-link basis, Cisco IOS requires a fully specified static route containing both the outbound interface and the next-hop link-local IP.
4
Set the administrative distance for floating route behavior.
Append '130' at the end of the command.
A primary OSPFv3 route has an administrative distance of 110. To function as a backup floating static route, the static route's administrative distance must be higher than 110.

Anahtar Kavram

Fully Specified IPv6 Floating Static Route Configuration
Soru 179Soru →

Refer to the following partial IPv4 routing table output from a Cisco router:

text
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

S* 0.0.0.0/0 [1/0] via 10.0.0.1
O 172.31.0.0/16 [110/20] via 10.1.1.1, GigabitEthernet0/0
D 172.31.50.0/24 [90/307200] via 10.2.2.2, GigabitEthernet0/1
S 172.31.50.96/28 [1/0] via 10.3.3.3, GigabitEthernet0/2

When the router receives an IP packet destined for 172.31.50.100172.31.50.100, which TWO statements correctly describe how the router makes its forwarding decision?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: The router selects the route 172.31.50.96/28 because it has the longest matching prefix length (/28) for destination 172.31.50.100.; The packet is forwarded out interface GigabitEthernet0/2 toward next-hop IP address 10.3.3.3.

Cevap

The router forwards the packet out interface GigabitEthernet0/2 toward next-hop 10.3.3.3 after selecting 172.31.50.96/28 as the longest prefix match.
When an IPv4 packet arrives, a router evaluates all matching routes in its routing table and selects the entry with the longest prefix length (most specific subnet mask). Here, destination 172.31.50.100 matches 0.0.0.0/0 (/0), 172.31.0.0/16 (/16), 172.31.50.0/24 (/24), and 172.31.50.96/28 (/28). The /28 route is the longest match. Therefore, the router forwards the packet out interface GigabitEthernet0/2 to next-hop 10.3.3.3.

Adım Adım Çözüm

1
Evaluate all routing table entries that match the destination IP address 172.31.50.100.
The destination matches four entries: 0.0.0.0/0, 172.31.0.0/16, 172.31.50.0/24, and 172.31.50.96/28.
All four network routes encompass the destination IP address 172.31.50.100.
2
Apply the Longest Prefix Match (LPM) rule to select the best route.
172.31.50.96/28 is chosen because /28 is the longest prefix mask (most specific match).
A router always prefers the route with the highest number of matching network bits before considering Administrative Distance or Metric.
3
Identify the next-hop IP and egress interface configured for the winning route.
The entry 172.31.50.96/28 specifies next-hop 10.3.3.3 and egress interface GigabitEthernet0/2.
The router uses the exact forwarding attributes bound to the selected longest matching route entry.

Anahtar Kavram

Router Forwarding Decision Logic (Longest Prefix Match)
Soru 180Soru →

Refer to the following routing table output from a Cisco router:

text
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2

Gateway of last resort is 10.1.1.1 to network 0.0.0.0

S* 0.0.0.0/0 [1/0] via 10.1.1.1
D 192.168.0.0/16 [90/307200] via 10.2.2.2, 01:45:12, GigabitEthernet0/0/1
O 192.168.4.0/24 [110/20] via 10.3.3.3, 00:12:34, GigabitEthernet0/0/2
S 192.168.4.128/26 [1/0] via 10.4.4.4
D 192.168.4.144/28 [90/281600] via 10.5.5.5, 00:05:10, GigabitEthernet0/0/3
O 192.168.4.148/30 [110/50] via 10.6.6.6, 00:01:20, GigabitEthernet0/0/4

The router receives an IP packet with a destination IP address of 192.168.4.150192.168.4.150. Which next-hop IP address will the router select to forward this packet, and for what reason?

Cevabı ve açıklamayı göster

Cevap: 10.6.6.6, because the 192.168.4.148/30 prefix provides the longest matching subnet mask for the destination address.

Cevap

The router selects next-hop 10.6.6.6 because 192.168.4.148/30 is the longest matching prefix for destination host 192.168.4.150.
When a router receives a packet, its forwarding engine determines the path by applying the Longest Prefix Match (LPM) rule. The destination address 192.168.4.150 matches multiple routes in the table (/16, /24, /26, /28, /30, and default /0). The route with prefix 192.168.4.148/30 has 30 matching bits, which is the most specific match. Administrative distance is only evaluated when a router receives routes for the exact same destination prefix length from different routing sources. Therefore, the packet is forwarded to next-hop 10.6.6.6.

Adım Adım Çözüm

1
Determine subnet boundaries for all matching routes in the routing table for IP address 192.168.4.150.
192.168.0.0/16 matches (192.168.0.0 - 192.168.255.255)
192.168.4.0/24 matches (192.168.4.0 - 192.168.4.255)
192.168.4.128/26 matches (192.168.4.128 - 192.168.4.191)
192.168.4.144/28 matches (192.168.4.144 - 192.168.4.159)
192.168.4.148/30 matches (192.168.4.148 - 192.168.4.151)
Identify all valid route entries in the Routing Information Base (RIB) that encompass the destination IP.
2
Compare prefix lengths among all matching entries.
Prefix lengths are /16, /24, /26, /28, and /30. The longest matching prefix length is /30.
Cisco routers use the Longest Prefix Match (LPM) rule to select the best route for packet forwarding.
3
Verify host IP validity within the selected /30 network.
Subnet 192.168.4.148/30 network address = 192.168.4.148, broadcast address = 192.168.4.151, usable host IP addresses = 192.168.4.149 and 192.168.4.150.
Confirming 192.168.4.150 is a valid unicast destination host IP within the /30 range.
4
Identify the next-hop IP associated with the longest matching route.
Route 192.168.4.148/30 points to next-hop IP 10.6.6.6 via interface GigabitEthernet0/0/4.
Administrative distance is only evaluated when identical prefixes are learned from multiple sources; since /30 is unique and longest, AD (110) is not compared against other prefixes.

Anahtar Kavram

Router Forwarding Decision Logic (Longest Prefix Match precedence over Administrative Distance and Metric)
Tahmini Süre:2m 0s
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