import re
data = '''1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 00:25:b5:12:02:00 brd ff:ff:ff:ff:ff:ff '''
p = re.compile(r'^\s*link/ether\s+([0-9a-fA-F]+(?::[0-9a-fA-F]+){5})\s+brd', re.M)
print(p.findall(data))

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