Exam 300-101 Question id=480 VPN Technologies

Refer to the exhibit. After configuring GRE between two routers running OSPF that are connected to each other via a WAN link, a network engineer notices that the two routers cannot establish the GRE tunnel to begin the exchange of routing updates. What is the reason for this?
q_103

A. Either a firewall between the two routers or an ACL on the router is blocking IP protocol number 47.
B. Either a firewall between the two routers or an ACL on the router is blocking UDP 57.
C. Either a firewall between the two routers or an ACL on the router is blocking TCP 47.
D. Either a firewall between the two routers or an ACL on the router is blocking IP protocol number 57.

WARNING

the answers are mixed, do not specify in the comment number or the letter of the answer
please write answer#A instead A, answer#B instead B...
Subject:

only logged users can write comments