OpenVPN Client Authentication without Certificates

I've been trying to get my OVPN server work without client-side certificate verification.

My server.conf contains the following:

# Ports & protocols
port 1194
proto udp
dev tun

# Server certs and keys
ca /etc/openvpn/keys/ca.crt
cert /etc/openvpn/keys/server.crt
key /etc/openvpn/keys/server.key  # This file should be kept secret
dh /etc/openvpn/keys/dh2048.pem

# Server subnet
server 198.18.200.0 255.255.255.0

# Persist IP lease pool
ifconfig-pool-persist ipp.txt

# Pushing to a private subnet
 push "route 192.168.10.234 255.255.255.0"

# Allowing duplicate common names for clients (no keys/certs)
duplicate-cn

# KeepAlive
keepalive 10 120

# Cryptographic cipher.
cipher AES-256-CBC

# privilege downgrade fix.
persist-key
persist-tun

# Output a short status log
status openvpn-status.log

# Verbosity level 4
verb 4

# Notify the client that when the server restarts
explicit-exit-notify 1

# Add PAM Auth plugin
plugin /usr/lib/openvpn/openvpn-plugin-auth-pam.so login

# No need for client cert
client-cert-not-required

and the client.conf file contains the following

# Define Client
client

dev tun

# protocol
proto udp-client

# Server
remote abc.efg.xyz

# Service port
port 1194

# Not binding to a specific port
nobind

# Try to preserve some state across restarts.
persist-key
persist-tun


# moderate verbosity
verb 4
mute 10

# Chosen yptographic cipher.
cipher AES-256-CBC

# cipher algorithm
auth SHA1

# Username and password are stored in this file
auth-user-pass f_secret

auth-nocache

I am unable to connect and when I checked the log, it is requiring me the CA file.

Options error: You must define CA file (--ca) or CA path (--capath)

Can someone please tell me, how can I avoid using the CA file?