Which of the following routing protocols does not support MD5 authentication for secure route updates? (Select
the best answer.)

A.
BGP

B.
OSPF

C.
RIPv1

D.
RIPv2

E.
EIGRP

Explanation:
Routing Information Protocol version 1 (RIPv1) does not support Message Digest 5 (MD5) authentication for
secure route updates. Routing protocol spoofing can inject false routes into routing tables, which can influence
path selection through a routed network. You can mitigate routing table modification by implementing routing
protocol authentication and filtering. RIPv1 does not support any form of authentication? however, its
successor, RIP version 2 (RIPv2), supports either plaintext authentication or MD5 authentication.
Border Gateway Protocol (BGP), Open Shortest Path First (OSPF), RIPv2, Enhanced Interior Gateway Routing
Protocol (EIGRP) all support MD5 authentication for secure route updates. Although many of these protocols,
such as OSPF, support plaintext authentication as an alternative to MD5, Cisco recommends using MD5 for
authentication because it is considerably more secure than plaintext authentication.
Alternatively, you can disable all dynamic routing protocols and use static routes to ensure that routes are
updated securely. However, static routes work well only on small, reliable networks. Static routes are not
scalable, because changes made on one router are not propagated to the other routers on the network? each
router must be modified manually.

Cisco: Network Foundation Protection: Restrict Routing Protocol Membership
Cisco: Sample Configuration for Authentication in RIPv2