A network engineer needs to connect two remote sites over an IPv4-only MPLS backbone. The sites use different routing protocols internally (OSPF at Site A, EIGRP at Site B) and must exchange routes between them. The engineer decides to use a static GRE tunnel between the two site edge routers. Which configuration step is essential to ensure the GRE tunnel can carry the routing protocol traffic between the sites?

Configure a static route on both routers pointing to the remote tunnel IP address via the physical interface.

Set the tunnel mode to multipoint GRE (mGRE) to support dynamic neighbors, as static GRE cannot carry routing protocols.

Configure the tunnel source and destination with the loopback addresses of the edge routers, and assign an IP address to the tunnel interface from a private subnet.

Enable IPsec on the tunnel interface to encrypt all traffic, since GRE does not provide any security by default.

A network architect is designing a solution to connect two data centers. The requirement is to carry both IPv4 and IPv6 traffic between the sites over an IPv4 WAN. The architect decides to use a single GRE tunnel. What is the main advantage of using GRE for this requirement?

GRE creates a separate tunnel for each protocol, ensuring isolation.

GRE can encapsulate both IPv4 and IPv6 packets, allowing a single tunnel to carry both protocols.

GRE automatically compresses the traffic to reduce bandwidth usage.

GRE provides built-in encryption for both IPv4 and IPv6 traffic.

A GRE tunnel is configured between two routers, but the tunnel interface is down. The engineer checks the configuration and finds that the tunnel destination is set to an IP address that is not reachable from the local router. What is the most likely reason the tunnel is down?

The tunnel keepalive is not configured, so the tunnel is down.

The tunnel interface IP address is in the same subnet as the physical interface, causing a conflict.

The tunnel source is not configured, so the tunnel cannot be established.

The router cannot encapsulate packets because the destination is unreachable, so the tunnel interface is down.

A GRE tunnel is configured between two routers. The tunnel interface is up/up, but users cannot reach the remote site. The engineer runs a ping from the local router to the remote tunnel IP and it succeeds. The engineer also checks the routing table and sees that the remote site's subnet is not present. The local router is running OSPF over the tunnel. What is the most likely cause of the problem?

The tunnel source and destination are swapped, causing OSPF to fail.

The tunnel keepalive is not configured, so OSPF cannot establish adjacency.

OSPF is not configured to advertise the remote site's subnet over the tunnel, or the tunnel is not included in the OSPF process.

The tunnel MTU is too small, causing OSPF hello packets to be dropped.

A GRE tunnel is configured between two routers. The tunnel is up, but large file transfers fail. The engineer suspects an MTU issue and wants to fix it without affecting other traffic. The physical interface MTU is 1500 bytes. What is the best configuration to solve the problem?

Set the physical interface MTU to 1524 bytes to accommodate the GRE header.

Set the tunnel interface MTU to 1500 bytes and enable fragmentation on the physical interface.

Disable the tunnel keepalive to reduce overhead and allow larger packets.

Set the tunnel interface MTU to 1476 bytes and enable TCP MSS clamping on the physical interface.

CCIE Enterprise Infrastructure

Domain 3Objective 1

Static Point-To-Point GRE Tunnels CCIE-ENTERPRISE-INFRASTRUCTURE Practice Questions (Page 6)

Part of the Transport Technologies and Solutions domain, which accounts for 15% of the CCIE-ENTERPRISE-INFRASTRUCTURE exam. Cisco does not publish an official question count, but from its 120-minute exam (~50–80 total, ~8–12 in this domain), expect 3–4 from this objective — we provide 42 practice questions to prepare you well beyond it. (estimate)

42questions here

9free pages

4concepts

15%of the exam

Questions 26–30

26application · medium
A network engineer needs to connect two remote sites over an IPv4-only MPLS backbone. The sites use different routing protocols internally (OSPF at Site A, EIGRP at Site B) and must exchange routes between them. The engineer decides to use a static GRE tunnel between the two site edge routers. Which configuration step is essential to ensure the GRE tunnel can carry the routing protocol traffic between the sites?
Select an answer first
27application · medium
A network architect is designing a solution to connect two data centers. The requirement is to carry both IPv4 and IPv6 traffic between the sites over an IPv4 WAN. The architect decides to use a single GRE tunnel. What is the main advantage of using GRE for this requirement?
Select an answer first
28application · medium
A GRE tunnel is configured between two routers, but the tunnel interface is down. The engineer checks the configuration and finds that the tunnel destination is set to an IP address that is not reachable from the local router. What is the most likely reason the tunnel is down?
Select an answer first
29expert · hard
A GRE tunnel is configured between two routers. The tunnel interface is up/up, but users cannot reach the remote site. The engineer runs a ping from the local router to the remote tunnel IP and it succeeds. The engineer also checks the routing table and sees that the remote site's subnet is not present. The local router is running OSPF over the tunnel. What is the most likely cause of the problem?
Select an answer first
30expert · hard
A GRE tunnel is configured between two routers. The tunnel is up, but large file transfers fail. The engineer suspects an MTU issue and wants to fix it without affecting other traffic. The physical interface MTU is 1500 bytes. What is the best configuration to solve the problem?
Select an answer first

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Static Point-To-Point GRE Tunnels CCIE-ENTERPRISE-INFRASTRUCTURE Practice Questions (Page 6)

Questions 26–30

A network architect is designing a solution to connect two data centers. The requirement is to carry both IPv4 and IPv6 traffic between the sites over an IPv4 WAN. The architect decides to use a single GRE tunnel. What is the main advantage of using GRE for this requirement?

A GRE tunnel is configured between two routers, but the tunnel interface is down. The engineer checks the configuration and finds that the tunnel destination is set to an IP address that is not reachable from the local router. What is the most likely reason the tunnel is down?

A GRE tunnel is configured between two routers. The tunnel is up, but large file transfers fail. The engineer suspects an MTU issue and wants to fix it without affecting other traffic. The physical interface MTU is 1500 bytes. What is the best configuration to solve the problem?

Keep studying — Transport Technologies and Solutions