diff --git a/env-ot41.sh b/env-ot41.sh
index e02f8f07..df37086b 100644
--- a/env-ot41.sh
+++ b/env-ot41.sh
@@ -1,4 +1,6 @@
+# em2 is management, em3 and em4 have no link to switch
 export MANAGEMENT_IF=em2
+export SKIP_IF=em2,em3,em4
 export NETLINK_LINE=1
 
 # allow to manually run perform tests frag and splice on netlink hosts
@@ -11,7 +13,7 @@ REMOTE_ADDR=undef
 REMOTE_ADDR6=undef
 REMOTE_SSH=undef
 export LOCAL_ADDR LOCAL_NET LOCAL_ADDR6 LOCAL_NET6
-export  REMOTE_ADDR REMOTE_ADDR6 REMOTE_SSH
+export REMOTE_ADDR REMOTE_ADDR6 REMOTE_SSH
 
 LOCAL_ADDR_RANGE=10.10.11.20
 LOCAL_ADDR6_RANGE=fdd7:e83e:66bd:1011::20
diff --git a/env-ot42.sh b/env-ot42.sh
index 0815dd36..6b681524 100644
--- a/env-ot42.sh
+++ b/env-ot42.sh
@@ -1,4 +1,6 @@
+# em4 is management, em5 is left over
 export MANAGEMENT_IF=em4
+export SKIP_IF=em4,em5
 export NETLINK_LINE=2
 
 # allow to manually run perform tests frag and splice on netlink hosts
diff --git a/net.pl b/net.pl
index f7b7b574..6ab1953f 100755
--- a/net.pl
+++ b/net.pl
@@ -139,10 +139,10 @@
 print $fh "TESTMODES ", join(" ", sort keys %testmode), "\n";
 close($fh);
 
-delete $ENV{MANAGEMENT_IF};
+delete $ENV{SKIP_IF};
 environment("$netlinkdir/bin/env-$host.sh");
-my $management_if = $ENV{MANAGEMENT_IF}
-    or die "MANAGEMENT_IF is not in 'env-$host.sh'";
+my $skip_if = $ENV{SKIP_IF} || "";
+$skip_if =~ s/,/|/;
 
 # setup remote machines
 
@@ -218,14 +218,14 @@ END
 	my %ifnums;
 	@ifnums{
 	    map { /^$iftype(\d+)$/ }
-	    grep { ! /^($management_if)$/ }
+	    grep { ! /^($skip_if)$/ }
 	    map { /^($iftype\d+) at / ? $1 : () }
 	    @dmesg} = ();
 	foreach my $ifnum (defined($num) ? ($num + 0) :
 	    pairkeys sort { $a <=> $b } keys %ifnums) {
-	    if (($iftype.($ifnum + 0)) =~ /^($management_if)$/ ||
-		($iftype.($ifnum + 1)) =~ /^($management_if)$/) {
-		die "Cannot use inferface '$if', conflicts management";
+	    if (($iftype.($ifnum + 0)) =~ /^($skip_if)$/ ||
+		($iftype.($ifnum + 1)) =~ /^($skip_if)$/) {
+		die "Cannot use inferface '$if', conflicts skip interface";
 	    }
 	    if (!exists($ifnums{$ifnum + 0}) || !exists($ifnums{$ifnum + 1})) {
 		if (defined($num)) {
diff --git a/netlink.pl b/netlink.pl
index 60b4e608..ab0b89e0 100755
--- a/netlink.pl
+++ b/netlink.pl
@@ -70,8 +70,8 @@
     $left_ifidx = 0;
     $right_ifidx = 1;
 }
-if (($iftype.$left_ifidx) =~ /^($management_if$/ ||
-    ($iftype.$right_ifidx) =~ /^($management_if$/) {
+if (($iftype.$left_ifidx) eq $management_if ||
+    ($iftype.$right_ifidx) eq $management_if) {
     if (defined($ifnum)) {
 	die "Cannot use inferface '$iface', conflicts management";
     } else {