SRWE MODULES 14–16 REVIEW | COMPLETE PRACTICE QUESTIONS, ANSWERS &
STUDY GUIDE 2026/2027
Reorder the following steps describing the packet forwarding process:
- The router encapsulates the packet in a data link frame and forwards it out the egress interface. The
destination could be a device connected to the network or a next-hop router.
- The router examines the destination IP address in the packet header and consults its IP routing table.
- The router finds the longest matching prefix in the routing table.
- The data link frame with an encapsulated IP packet arrives on the ingress interface.
- However, if there is no matching route entry the packet is dropped. - correct answer ✔✔1. The data
link frame with an encapsulated IP packet arrives on the ingress interface.
2. The router examines the destination IP address in the packet header and consults its IP routing table.
3. The router finds the longest matching prefix in the routing table.
4. The router encapsulates the packet in a data link frame and forwards it out the egress interface. The
destination could be a device connected to the network or a next-hop router.
5. However, if there is no matching route entry the packet is dropped.
Define Path Determination - correct answer ✔✔The primary functions of a router are to determine the
best path to forward packets based on the information in its routing table, and to forward packets
toward their destination.
Define Longest Match - correct answer ✔✔The longest match is the route in the routing table that has
the greatest number of far-left matching bits (longest subnet mask) with the destination IP address of
the packet.
What is a Directly Connected Network? - correct answer ✔✔Directly connected networks are networks
that are configured on the active interfaces of a router. A directly connected network is added to the
routing table when an interface is configured with an IP address and subnet mask (prefix length) and is
active (up and up).
Remote networks are learned via what two methods? - correct answer ✔✔Static and dynamic routing
What are a routers three options for handling a packet? - correct answer ✔✔1. Forward it to a directly
connected network.
2. Forward it to a next-hop router.
3. Drop the packet
Define Process Switching - correct answer ✔✔An older packet forwarding mechanism. When a packet
arrives on an interface, it is forwarded to the control plane where the CPU matches the destination
address with an entry in its routing table, and then determines the exit interface and forwards the
, packet. It is important to understand that the router does this for EVERY packet, even if the destination is
the same for a stream of packets.
Define Fast Switching - correct answer ✔✔Fast switching uses a fast-switching cache to store next-hop
information. When a packet arrives on an interface, it is forwarded to the control plane where the CPU
searches for a match in the fast-switching cache. If it is not there, it is process-switched and forwarded to
the exit interface. The flow information for the packet is also stored in the fast-switching cache. If
another packet going to the same destination arrives on an interface, the next-hop information in the
cache is re-used without CPU intervention.
Define Cisco Express Forwarding (CEF) - correct answer ✔✔CEF is the most recent and default Cisco IOS
packet-forwarding mechanism. Like fast switching, CEF builds a Forwarding Information Base (FIB), and
an adjacency table. However, the table entries are not packet-triggered like fast switching but change-
triggered, such as when something changes in the network topology.
What is the Forwarding Information Base (FIB)? - correct answer ✔✔A data structure that contains all
routes known. Conceptually the FIB is similar to a routing table. A networking device uses the FIB lookup
table to make destination-based switching decisions.
What is the Adjacency Table - correct answer ✔✔A table used by CEF to collect the MAC addresses of
nodes that can be reached in a single Layer 2 hop. Conceptually similar to the ARP cache.
There are several configuration and verification commands for routers, including... - correct answer
✔✔show ip(v6) route, show ip(v6) interface, show ip(v6) interface brief and show running-config
To reduce the amount of command output, use a filter. Filtering commands can be used to display
specific sections of output. The filtering parameters that can be configured after the pipe include... -
correct answer ✔✔section - Shows entire section that starts with the filtering expression
include - Includes all output lines that match the filtering expression
exclude - Excludes all output lines that match the filtering expression
begin - Shows all the output lines from a certain point, starting with the line that matches the filtering
expression
The code "L" in a routing table indicates what? - correct answer ✔✔Identifies the address assigned to a
router interface. This allows the router to efficiently determine when it receives a packet for the
interface instead of being forwarded. "To it, not through it."
The code "C" in a routing table indicates what? - correct answer ✔✔Identifies a directly connected
network.
The code "S" in a routing table indicates what? - correct answer ✔✔Identifies a static route created to
reach a specific network.
The code "O" in a routing table indicates what? - correct answer ✔✔Identifies a dynamically learned
network from another router using the OSPF routing protocol.
STUDY GUIDE 2026/2027
Reorder the following steps describing the packet forwarding process:
- The router encapsulates the packet in a data link frame and forwards it out the egress interface. The
destination could be a device connected to the network or a next-hop router.
- The router examines the destination IP address in the packet header and consults its IP routing table.
- The router finds the longest matching prefix in the routing table.
- The data link frame with an encapsulated IP packet arrives on the ingress interface.
- However, if there is no matching route entry the packet is dropped. - correct answer ✔✔1. The data
link frame with an encapsulated IP packet arrives on the ingress interface.
2. The router examines the destination IP address in the packet header and consults its IP routing table.
3. The router finds the longest matching prefix in the routing table.
4. The router encapsulates the packet in a data link frame and forwards it out the egress interface. The
destination could be a device connected to the network or a next-hop router.
5. However, if there is no matching route entry the packet is dropped.
Define Path Determination - correct answer ✔✔The primary functions of a router are to determine the
best path to forward packets based on the information in its routing table, and to forward packets
toward their destination.
Define Longest Match - correct answer ✔✔The longest match is the route in the routing table that has
the greatest number of far-left matching bits (longest subnet mask) with the destination IP address of
the packet.
What is a Directly Connected Network? - correct answer ✔✔Directly connected networks are networks
that are configured on the active interfaces of a router. A directly connected network is added to the
routing table when an interface is configured with an IP address and subnet mask (prefix length) and is
active (up and up).
Remote networks are learned via what two methods? - correct answer ✔✔Static and dynamic routing
What are a routers three options for handling a packet? - correct answer ✔✔1. Forward it to a directly
connected network.
2. Forward it to a next-hop router.
3. Drop the packet
Define Process Switching - correct answer ✔✔An older packet forwarding mechanism. When a packet
arrives on an interface, it is forwarded to the control plane where the CPU matches the destination
address with an entry in its routing table, and then determines the exit interface and forwards the
, packet. It is important to understand that the router does this for EVERY packet, even if the destination is
the same for a stream of packets.
Define Fast Switching - correct answer ✔✔Fast switching uses a fast-switching cache to store next-hop
information. When a packet arrives on an interface, it is forwarded to the control plane where the CPU
searches for a match in the fast-switching cache. If it is not there, it is process-switched and forwarded to
the exit interface. The flow information for the packet is also stored in the fast-switching cache. If
another packet going to the same destination arrives on an interface, the next-hop information in the
cache is re-used without CPU intervention.
Define Cisco Express Forwarding (CEF) - correct answer ✔✔CEF is the most recent and default Cisco IOS
packet-forwarding mechanism. Like fast switching, CEF builds a Forwarding Information Base (FIB), and
an adjacency table. However, the table entries are not packet-triggered like fast switching but change-
triggered, such as when something changes in the network topology.
What is the Forwarding Information Base (FIB)? - correct answer ✔✔A data structure that contains all
routes known. Conceptually the FIB is similar to a routing table. A networking device uses the FIB lookup
table to make destination-based switching decisions.
What is the Adjacency Table - correct answer ✔✔A table used by CEF to collect the MAC addresses of
nodes that can be reached in a single Layer 2 hop. Conceptually similar to the ARP cache.
There are several configuration and verification commands for routers, including... - correct answer
✔✔show ip(v6) route, show ip(v6) interface, show ip(v6) interface brief and show running-config
To reduce the amount of command output, use a filter. Filtering commands can be used to display
specific sections of output. The filtering parameters that can be configured after the pipe include... -
correct answer ✔✔section - Shows entire section that starts with the filtering expression
include - Includes all output lines that match the filtering expression
exclude - Excludes all output lines that match the filtering expression
begin - Shows all the output lines from a certain point, starting with the line that matches the filtering
expression
The code "L" in a routing table indicates what? - correct answer ✔✔Identifies the address assigned to a
router interface. This allows the router to efficiently determine when it receives a packet for the
interface instead of being forwarded. "To it, not through it."
The code "C" in a routing table indicates what? - correct answer ✔✔Identifies a directly connected
network.
The code "S" in a routing table indicates what? - correct answer ✔✔Identifies a static route created to
reach a specific network.
The code "O" in a routing table indicates what? - correct answer ✔✔Identifies a dynamically learned
network from another router using the OSPF routing protocol.
