CCNA IP Routing Practice Question
A company wants to connect two sites across an IP network by creating a logical tunnel between the edge routers. Which technology is most directly associated with that requirement?
⚠ Common exam trap
A common exam trap is mistaking GRE for unrelated Cisco features like PortFast or DHCP relay. PortFast is a Spanning Tree Protocol optimization for edge ports and does not create tunnels. DHCP relay forwards DHCP requests and is unrelated to site-to-site connectivity. Another trap is confusing GRE with security features like IPsec; GRE itself does not encrypt traffic but only encapsulates it. Candidates might also overlook that GRE tunnels require proper MTU handling to avoid fragmentation issues, which can cause connectivity problems if ignored.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
GRE
GRE is the most directly associated technology because it creates a logical tunnel between routers across an existing IP network. In practical terms, it allows the routers to treat the path as a virtual point-to-point connection for encapsulated traffic. The question is specifically about tunneling between sites, not about plain routing, management, or switching behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
GRE
Why this is correct
Generic Routing Encapsulation (GRE) is a tunneling protocol that takes an entire packet and encapsulates it inside another IP packet, effectively creating a logical point-to-point link between two routers across an IP network. By configuring a GRE tunnel on each site's edge router, the two sites can exchange private addresses and routing information as if they were directly connected on the same link. This makes GRE a standard solution for site-to-site connectivity over IP networks, because it provides a simple, logical path for arbitrary payload traffic.
- ✗
PortFast
Why it's wrong here
PortFast is a Spanning Tree Protocol feature that immediately transitions a switch port to the forwarding state, bypassing the normal listening and learning states, and is intended only for ports connected to end-user devices. It has no mechanism to encapsulate or carry packets across an IP network, nor does it create any logical link between separate locations. Thus, it cannot serve to connect two sites over an IP network, because its role is limited to speeding up STP convergence on edge ports.
When this WOULD be correct
If the question asked about optimizing switch port behavior in a network where rapid connectivity is needed for end devices, PortFast would be the correct answer. For example, a scenario involving a network with multiple switches where minimizing downtime during network topology changes is critical would validate its use.
- ✗
DHCP relay
Why it's wrong here
DHCP relay, commonly configured with the ip helper-address command, is a Layer 3 feature that takes a client's DHCP broadcast message and forwards it as a unicast packet to a DHCP server on another subnet, then relays the server's reply back to the client. This mechanism is specifically for dynamic host configuration and operates on only the DHCP message types exchanged between client and server. It does not establish a persistent logical tunnel or transport site-to-site application traffic, making it unsuitable for connecting two sites over an IP network.
When this WOULD be correct
If the question asked about connecting clients to a DHCP server located on a different subnet, where the relay agent is required to forward DHCP messages, then DHCP relay would be the correct answer. This scenario focuses on DHCP functionality rather than tunneling.
- ✗
Root guard
Why it's wrong here
Root guard is a Spanning Tree Protocol protection feature that monitors a switch port and blocks it from becoming the root port if a superior BPDU arrives, thereby preventing unauthorized switches from hijacking STP root status. This function works only within Layer 2 STP domain and is concerned solely with loop prevention and topology control. It has no ability to tunnel traffic, encapsulate packets, or forward data between remote locations, so it cannot connect two sites across an IP network.
When this WOULD be correct
If the exam question asked about securing the spanning tree topology in a network with multiple switches, where preventing rogue switches from becoming the root bridge is critical, then root guard would be the correct answer. This scenario would focus on maintaining network stability rather than tunneling.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓GRECorrect answer▾
Why this is correct
Generic Routing Encapsulation (GRE) is a tunneling protocol that takes an entire packet and encapsulates it inside another IP packet, effectively creating a logical point-to-point link between two routers across an IP network. By configuring a GRE tunnel on each site's edge router, the two sites can exchange private addresses and routing information as if they were directly connected on the same link. This makes GRE a standard solution for site-to-site connectivity over IP networks, because it provides a simple, logical path for arbitrary payload traffic.
✗PortFastWrong answer — click to see why▾
Why this is wrong here
PortFast is a Cisco switch feature that immediately transitions a port to the forwarding state, bypassing the Spanning Tree Protocol (STP) listening and learning phases. It is used for access ports connected to end devices, not for creating tunnels between sites.
★ When this WOULD be the correct answer
If the question asked about optimizing switch port behavior in a network where rapid connectivity is needed for end devices, PortFast would be the correct answer. For example, a scenario involving a network with multiple switches where minimizing downtime during network topology changes is critical would validate its use.
Why candidates choose this
Students might confuse PortFast with a feature that speeds up network connectivity, but it is unrelated to tunneling or site-to-site connections.
✗DHCP relayWrong answer — click to see why▾
Why this is wrong here
DHCP relay is a feature that forwards DHCP broadcast requests from clients on one subnet to a DHCP server on another subnet. It does not create a logical tunnel between sites; it simply helps with IP address assignment across subnets.
★ When this WOULD be the correct answer
If the question asked about connecting clients to a DHCP server located on a different subnet, where the relay agent is required to forward DHCP messages, then DHCP relay would be the correct answer. This scenario focuses on DHCP functionality rather than tunneling.
Why candidates choose this
The term 'relay' might suggest forwarding traffic between networks, leading students to think it could be used for site-to-site connectivity, but it is not a tunneling technology.
✗Root guardWrong answer — click to see why▾
Why this is wrong here
Root guard is a Spanning Tree Protocol (STP) feature that prevents a switch port from becoming the root port, enforcing the root bridge location. It is used to protect the STP topology, not to create tunnels between sites.
★ When this WOULD be the correct answer
If the exam question asked about securing the spanning tree topology in a network with multiple switches, where preventing rogue switches from becoming the root bridge is critical, then root guard would be the correct answer. This scenario would focus on maintaining network stability rather than tunneling.
Why candidates choose this
The word 'guard' might imply a security or connectivity feature, but root guard is specifically for STP and has no role in tunneling.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
GRE
GRE (Generic Routing Encapsulation) is a tunneling protocol that encapsulates packets inside other packets to transport them across incompatible networks.
Key term
GRE
Generic Routing Encapsulation is a tunneling protocol that wraps packets of one protocol inside another protocol to transport them across an intermediary network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.