diff --git a/tests/atf_python/sys/net/vnet.py b/tests/atf_python/sys/net/vnet.py
--- a/tests/atf_python/sys/net/vnet.py
+++ b/tests/atf_python/sys/net/vnet.py
@@ -103,6 +103,7 @@
         if1 = cls(alias_name, name)
         ret = [if1]
         if name.startswith("epair"):
+            run_cmd("/sbin/ifconfig {} -txcsum -txcsum6".format(name))
             if2 = cls(alias_name, name[:-1] + "b")
             if1.epairb = if2
             ret.append(if2);
diff --git a/tests/sys/common/vnet.subr b/tests/sys/common/vnet.subr
--- a/tests/sys/common/vnet.subr
+++ b/tests/sys/common/vnet.subr
@@ -42,6 +42,11 @@
 vnet_mkepair()
 {
 	ifname=$(ifconfig epair create)
+	# When transmit checksum offloading is enabled, if_epair does not
+	# compute checksums, it just marks packets that this computation still
+	# needs to be done. However, some test cases verify the checksum.
+	# Therefore disable this for IPv4 and IPv6.
+	ifconfig ${ifname} -txcsum -txcsum6
 	list_interface $ifname
 	list_interface ${ifname%a}b
 	echo ${ifname%a}