import re
p = re.compile(r'(tengig.*?(?:\n+)?\bmtu\b.*?(?:\n+)?\bcarrier-delay\b[^\n]+)', re.MULTILINE | re.IGNORECASE)
test_str = "port0 interface GigabitEthernet0/4/0\n\nport1 interface TenGigabitEthernet0/1/0\n\nlogin delay 2\n\nbfd-template single-hop BDI\n\nip ftp source-interface Loopback0\n\nip tftp source-interface Loopback0\n\ninterface Loopback0\n\ninterface Loopback100\n\ninterface Loopback999\n\ndescription * Loopback interface for management *\n\ninterface TenGigabitEthernet0/0/0\n\nmtu 9216\n\ncarrier-delay msec 0\n\ninterface TenGigabitEthernet0/1/0\n\nmtu 9216\n\ncarrier-delay msec 0\n\ninterface GigabitEthernet0/4/0\n\nmtu 9216\n\ninterface GigabitEthernet0/4/1\n"
 
print(re.findall(p, test_str))

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