diff --git a/xCAT-server/lib/xcat/plugins/dhcp.pm b/xCAT-server/lib/xcat/plugins/dhcp.pm
index 0d579aa57..322abb598 100644
--- a/xCAT-server/lib/xcat/plugins/dhcp.pm
+++ b/xCAT-server/lib/xcat/plugins/dhcp.pm
@@ -232,22 +232,41 @@ sub _isc_static_host_fallback
 
 sub _delete_isc_static_host
 {
-    my $node = shift;
+    my ($node, $config, $hostname) = @_;
+    $config ||= \@dhcpconf;
+
+    my $start_marker = defined($hostname)
+      ? qr/^#xCAT host declaration for \Q$node\E aka host \Q$hostname\E start$/
+      : qr/^#xCAT host declaration for \Q$node\E aka host .* start$/;
+    my $end_marker = defined($hostname)
+      ? qr/^(?:\}\s*)?#xCAT host declaration for \Q$node\E aka host \Q$hostname\E end$/
+      : qr/^(?:\}\s*)?#xCAT host declaration for \Q$node\E aka host .* end$/;
 
     my @updated;
     my $skip = 0;
-    foreach my $line (@dhcpconf) {
-        if ($line =~ /^#xCAT host declaration for \Q$node\E\b.* start$/) {
+    foreach my $line (@{$config}) {
+        if ($line =~ $start_marker) {
             $skip = 1;
             next;
         }
-        if ($skip && $line =~ /^#xCAT host declaration for \Q$node\E\b.* end$/) {
+        if ($skip && $line =~ $end_marker) {
             $skip = 0;
             next;
         }
         push @updated, $line unless $skip;
     }
-    @dhcpconf = @updated;
+    @{$config} = @updated;
+}
+
+sub _begin_isc_static_host_update
+{
+    my ($node, $enabled, $config) = @_;
+
+    return 0 unless $enabled;
+    $config ||= \@dhcpconf;
+    my $line_count = scalar(@{$config});
+    _delete_isc_static_host($node, $config);
+    return scalar(@{$config}) != $line_count;
 }
 
 sub _static_host_statements
@@ -261,21 +280,51 @@ sub _static_host_statements
     return $statements;
 }
 
+sub _node_host_statements
+{
+    my ($node, $statements) = @_;
+
+    return 'ddns-hostname \"' . $node . '\"; send host-name \"'
+      . $node . '\";' . ($statements || '');
+}
+
+sub _noip_hostname
+{
+    my ($node, $mac) = @_;
+    my $hostname = $node . '-noip' . $mac;
+    $hostname =~ s/://g;
+    return $hostname;
+}
+
 sub _add_isc_static_host
 {
-    my ($node, $hostname, $mac, $ip, $statements) = @_;
+    my ($node, $hostname, $mac, $hardwaretype, $mgtifname, $ip, $statements,
+        $has_infiniband_identity, $config, $update_started) = @_;
+    $config ||= \@dhcpconf;
 
     return unless $ip && $ip ne 'DENIED';
 
-    _delete_isc_static_host($node);
+    if ($update_started && !${$update_started}) {
+        $restartdhcp = 1 if _begin_isc_static_host_update($node, 1, $config);
+        ${$update_started} = 1;
+    }
+
+    $mac = normalize_mac($mac) || $mac;
+    _delete_isc_static_host($node, $config, $hostname);
 
     my $host_statements = _static_host_statements($statements);
-    push @dhcpconf, "#xCAT host declaration for $node aka host $hostname start\n";
-    push @dhcpconf, "host $hostname {\n";
-    push @dhcpconf, "    hardware ethernet $mac;\n";
-    push @dhcpconf, "    fixed-address $ip;\n";
-    push @dhcpconf, "    $host_statements\n" if $host_statements;
-    push @dhcpconf, "} #xCAT host declaration for $node aka host $hostname end\n";
+    my $hardware_kind = $hardwaretype == 32 ? 'infiniband' : 'ethernet';
+    push @{$config}, "#xCAT host declaration for $node aka host $hostname start\n";
+    push @{$config}, "host $hostname {\n";
+    push @{$config}, "    hardware $hardware_kind $mac;\n";
+    push @{$config}, "    fixed-address $ip;\n";
+    push @{$config}, "    $host_statements\n" if $host_statements;
+    push @{$config}, "}\n";
+    push @{$config}, _infiniband_twin_static_lines(
+        $hostname, $mac, $hardwaretype, $mgtifname, $ip,
+        $host_statements, $has_infiniband_identity
+    );
+    push @{$config}, "#xCAT host declaration for $node aka host $hostname end\n";
 
     $restartdhcp = 1;
 }
@@ -491,6 +540,7 @@ sub delnode
     if ($ent and $ent->{mac})
     {
         my @macs = split(/\|/, $ent->{mac});
+        my $has_infiniband_identity = _infiniband_identity_present(@macs);
         my $mace;
         my $count = 0;
         foreach $mace (@macs)
@@ -505,13 +555,19 @@ sub delnode
             }    #Default to hostname equal to nodename
             unless ($mac) { next; }    #Skip corrupt format
 
-            if (!grep /:/, $mac) {
+            my $normalized_mac = normalize_mac($mac);
+            if ($normalized_mac) {
+                $mac = $normalized_mac;
+            } elsif (!grep /:/, $mac) {
                 $mac = lc($mac);
                 $mac =~ s/(\w{2})/$1:/g;
                 $mac =~ s/:$//;
             }
             my $hostname       = $hname;
             my %client_nethash = xCAT::DBobjUtils->getNetwkInfo([$node]);
+            my $hardwaretype = _hardware_type_for(
+                $mac, $client_nethash{$node}{mgtifname}
+            );
             if ($client_nethash{$node}{mgtifname} =~ /hf/)
             {
                 if (scalar(@macs) > 1) {
@@ -532,14 +588,21 @@ sub delnode
             print $omshell "remove\n";
             print $omshell "close\n";
 
-            if ($mac)
+            my ($ibnamecommands, $ibaddresscommands) =
+              _infiniband_twin_delete_commands(
+                $hostname, $mac, $hardwaretype,
+                $client_nethash{$node}{mgtifname},
+                _omapi_pre_create_cleanup_supported(),
+                $has_infiniband_identity
+              );
+            print $omshell $ibnamecommands if ($ibnamecommands);
+
+            my $hardwarecommands =
+              _hardware_address_delete_commands($mac, $hardwaretype);
+            if ($hardwarecommands)
             {
-                print $omshell "new host\n";
-                print $omshell "set hardware-address = " . $mac
-                  . "\n";                      #find and destroy mac conflict
-                print $omshell "open\n";
-                print $omshell "remove\n";
-                print $omshell "close\n";
+                print $omshell $hardwarecommands;
+                print $omshell $ibaddresscommands if ($ibaddresscommands);
             }
             if ($inetn and _omapi_ip_lookup_supported())
             {
@@ -649,6 +712,182 @@ sub addnode6 {
 
 }
 
+sub _infiniband_twin_mac
+{
+    my $mac = shift;
+
+    $mac = normalize_mac($mac);
+    return unless defined($mac) and length($mac) == 17;
+    return substr($mac, 0, 8) . ":03:00" . substr($mac, 8);
+}
+
+sub _infiniband_identity_present
+{
+    foreach my $entry (@_) {
+        my ($address) = split(/!/, $entry);
+        $address = normalize_mac($address);
+        return 1
+          if defined($address)
+          && (length($address) == 23 || length($address) == 26);
+    }
+    return 0;
+}
+
+sub _hardware_type_for
+{
+    my ($mac, $mgtifname) = @_;
+
+    return 37 if defined($mgtifname) && $mgtifname =~ /hf/;
+    $mac = normalize_mac($mac) || $mac || '';
+    return 32 if length($mac) == 23 || length($mac) == 26;
+    return 1;
+}
+
+sub _is_infiniband_interface
+{
+    my $mgtifname = shift;
+    return defined($mgtifname) && $mgtifname =~ /(?:^|!)ib[^!]*(?:!|$)/;
+}
+
+sub _infiniband_twin_identity
+{
+    my ($hostname, $mac, $hardwaretype, $mgtifname,
+        $has_infiniband_identity) = @_;
+    my $ibmac = _infiniband_twin_mac($mac);
+
+    return if $hardwaretype != 1
+      || !$ibmac
+      || !_is_infiniband_interface($mgtifname)
+      || $has_infiniband_identity;
+    return ("$hostname-xcat-ib", $ibmac);
+}
+
+sub _infiniband_twin_create_commands
+{
+    my ($hostname, $mac, $hardwaretype, $mgtifname, $ip, $hoststatements,
+        $cleanup_supported, $has_infiniband_identity) = @_;
+    my ($ibhostname, $ibmac) = _infiniband_twin_identity(
+        $hostname, $mac, $hardwaretype, $mgtifname,
+        $has_infiniband_identity
+    );
+
+    return unless $ibmac;
+
+    my $commands = '';
+    if ($cleanup_supported && _is_infiniband_interface($mgtifname)) {
+        $commands .= "new host\n"
+          . "set name = \"$ibhostname\"\n"
+          . "open\n"
+          . "remove\n"
+          . "close\n";
+    }
+    $commands .= "new host\n"
+      . "set name = \"$ibhostname\"\n"
+      . "set hardware-address = $ibmac\n"
+      . "set dhcp-client-identifier = $ibmac\n"
+      . "set hardware-type = 32\n";
+
+    if ($ip eq "DENIED") {
+        $commands .= "set statements = \"deny booting;\"\n";
+    } else {
+        $commands .= "set ip-address = $ip\n" if ($ip);
+        $commands .= "set statements = \"$hoststatements\"\n" if ($hoststatements);
+    }
+
+    return $commands . "create\nclose\n";
+}
+
+sub _infiniband_twin_static_lines
+{
+    my ($hostname, $mac, $hardwaretype, $mgtifname, $ip, $hoststatements,
+        $has_infiniband_identity) = @_;
+    my ($ibhostname, $ibmac) = _infiniband_twin_identity(
+        $hostname, $mac, $hardwaretype, $mgtifname,
+        $has_infiniband_identity
+    );
+
+    return unless $ibmac && $ip && $ip ne 'DENIED';
+
+    my @lines = (
+        "host $ibhostname {\n",
+        "    hardware infiniband $ibmac;\n",
+        "    fixed-address $ip;\n",
+    );
+    push @lines, "    $hoststatements\n" if $hoststatements;
+    push @lines, "}\n";
+    return @lines;
+}
+
+sub _infiniband_twin_delete_commands
+{
+    my ($hostname, $mac, $hardwaretype, $mgtifname, $cleanup_supported,
+        $has_infiniband_identity) = @_;
+    my $ibmac = _infiniband_twin_mac($mac);
+    return unless $ibmac;
+    if (!$cleanup_supported) {
+        my (undef, $current_ibmac) = _infiniband_twin_identity(
+            $hostname, $mac, $hardwaretype, $mgtifname,
+            $has_infiniband_identity
+        );
+        return unless $current_ibmac;
+    }
+    my $ibhostname = "$hostname-xcat-ib";
+
+    my $namecommands = "new host\n"
+      . "set name = \"$ibhostname\"\n"
+      . "open\n"
+      . "remove\n"
+      . "close\n";
+    my $addresscommands;
+
+    if ($cleanup_supported && _is_infiniband_interface($mgtifname)) {
+        $addresscommands = "new host\n"
+          . "set hardware-address = $ibmac\n"
+          . "set hardware-type = 32\n"
+          . "open\n"
+          . "remove\n"
+          . "close\n";
+    }
+
+    return ($namecommands, $addresscommands);
+}
+
+sub _hardware_address_delete_commands
+{
+    my ($mac, $hardwaretype) = @_;
+    return unless $mac;
+
+    my $commands = "new host\n"
+      . "set hardware-address = $mac\n";
+    $commands .= "set hardware-type = $hardwaretype\n"
+      if $hardwaretype != 1;
+
+    return $commands . "open\nremove\nclose\n";
+}
+
+sub _infiniband_twin_update_commands
+{
+    my ($hostname, $mac, $hardwaretype, $mgtifname, $ip, $hoststatements,
+        $cleanup_supported, $has_infiniband_identity) = @_;
+    my ($namecommands, $addresscommands);
+
+    if ($cleanup_supported) {
+        ($namecommands, $addresscommands) =
+          _infiniband_twin_delete_commands(
+            $hostname, $mac, $hardwaretype, $mgtifname,
+            $cleanup_supported, $has_infiniband_identity
+          );
+        undef $addresscommands if $has_infiniband_identity;
+    }
+    my $createcommands = _infiniband_twin_create_commands(
+        $hostname, $mac, $hardwaretype, $mgtifname, $ip,
+        $hoststatements, 0, $has_infiniband_identity
+    );
+
+    return ($namecommands, $addresscommands, $createcommands);
+}
+
+
 sub addnode
 {
 
@@ -772,6 +1011,9 @@ sub addnode
     }
 
     my @macs = split(/\|/, $ent->{mac});
+    my $has_infiniband_identity = _infiniband_identity_present(@macs);
+    my $static_host_fallback = _isc_static_host_fallback();
+    my $static_host_update_started = 0;
     my $mace;
     my $deflstaments = $lstatements;
     my $count        = 0;
@@ -797,10 +1039,11 @@ sub addnode
             );
             next;
         }
+        my $noip_mac = $mac;
+        $mac = normalize_mac($mac);
         my $ip = getipaddr($hname, OnlyV4 => 1);
         if ($hname eq '*NOIP*') {
-            $hname = $node . "-noip" . $mac;
-            $hname =~ s/://g;
+            $hname = _noip_hostname($node, $noip_mac);
             $ip = 'DENIED';
 
             #        } #if 'guess_next_server', inherit from the network provided value... see how this pans out
@@ -928,17 +1171,13 @@ sub addnode
         }
         else
         {
-            if (!grep /:/, $mac) {
-                $mac = lc($mac);
-                $mac =~ s/(\w{2})/$1:/g;
-                $mac =~ s/:$//;
-            }
             my $hostname       = $hname;
-            my $hardwaretype   = 1;
             my %client_nethash = xCAT::DBobjUtils->getNetwkInfo([$node]);
-            if ($client_nethash{$node}{mgtifname} =~ /hf/)
+            my $hardwaretype = _hardware_type_for(
+                $mac, $client_nethash{$node}{mgtifname}
+            );
+            if ($hardwaretype == 37)
             {
-                $hardwaretype = 37;
                 if (scalar(@macs) > 1) {
                     if ($hname !~ /^(.*)-hf(.*)$/) {
                         $hostname = $hname . "-hf" . $count;
@@ -946,27 +1185,35 @@ sub addnode
                         $hostname = $1 . "-hf" . $count;
                     }
                 }
-            } elsif (length($mac) == 23 || length($mac) == 26) { # 8 or 9 bytes of mac address
-		# Currently the only thing that has 8 or 9 bytes is an infiniband
-		# or infiniband like device, which is type 32 (0x20).
-                $hardwaretype = 32;
             }
 
-            if (_isc_static_host_fallback()) {
+            if ($static_host_fallback) {
                 if ($ip ne "DENIED") {
-                    if ($lstatements) {
-                        $lstatements = 'ddns-hostname \"' . $node . '\"; send host-name \"' . $node . '\";' . $lstatements;
-                    } else {
-                        $lstatements = 'ddns-hostname \"' . $node . '\"; send host-name \"' . $node . '\";';
-                    }
+                    $lstatements = _node_host_statements($node, $lstatements);
                 } else {
                     $lstatements = "deny booting;";
                 }
-                _add_isc_static_host($node, $hostname, $mac, $ip, $lstatements);
+                _add_isc_static_host(
+                    $node, $hostname, $mac, $hardwaretype,
+                    $client_nethash{$node}{mgtifname}, $ip, $lstatements,
+                    $has_infiniband_identity, undef,
+                    \$static_host_update_started
+                );
                 $count = $count + 2;
                 next;
             }
 
+            if ($ip ne "DENIED") {
+                $lstatements = _node_host_statements($node, $lstatements);
+            }
+            my ($ibnamecommands, $ibaddresscommands, $ibcreatecommands) =
+              _infiniband_twin_update_commands(
+                $hostname, $mac, $hardwaretype,
+                $client_nethash{$node}{mgtifname}, $ip, $lstatements,
+                _omapi_pre_create_cleanup_supported(),
+                $has_infiniband_identity
+              );
+
             #syslog("local4|err", "Setting $node ($hname|$ip) to " . $mac);
             if (_omapi_pre_create_cleanup_supported()) {
                 print $omshell "new host\n";
@@ -975,6 +1222,7 @@ sub addnode
                 print $omshell "open\n";
                 print $omshell "remove\n";
                 print $omshell "close\n";
+                print $omshell $ibnamecommands if ($ibnamecommands);
             }
             if ($ip and $ip ne 'DENIED' and _omapi_ip_lookup_supported()) {
                 print $omshell "new host\n";
@@ -984,12 +1232,9 @@ sub addnode
                 print $omshell "close\n";
             }
             if (_omapi_pre_create_cleanup_supported()) {
-                print $omshell "new host\n";
-                print $omshell "set hardware-address = " . $mac
-                  . "\n";    #find and destroy mac conflict
-                print $omshell "open\n";
-                print $omshell "remove\n";
-                print $omshell "close\n";
+                print $omshell
+                  _hardware_address_delete_commands($mac, $hardwaretype);
+                print $omshell $ibaddresscommands if ($ibaddresscommands);
             }
             print $omshell "new host\n";
             print $omshell "set name = \"$hostname\"\n";
@@ -1006,18 +1251,12 @@ sub addnode
                 if ($ip) {
                     print $omshell "set ip-address = $ip\n";
                 }
-                if ($lstatements)
-                {
-                    $lstatements = 'ddns-hostname \"' . $node . '\"; send host-name \"' . $node . '\";' . $lstatements;
-
-                } else {
-                    $lstatements = 'ddns-hostname \"' . $node . '\"; send host-name \"' . $node . '\";';
-                }
                 print $omshell "set statements = \"$lstatements\"\n";
             }
 
             print $omshell "create\n";
             print $omshell "close\n";
+            print $omshell $ibcreatecommands if ($ibcreatecommands);
             unless ($::XCATSITEVALS{externaldhcpservers}) {
                 unless (grep /#definition for host $node aka host $hostname/, @dhcpconf)
                 {
@@ -3319,7 +3558,7 @@ sub kea_xnba_client_classes_for_nodes
     );
 }
 
-sub kea_normalize_mac
+sub normalize_mac
 {
     my ($mac) = @_;
 
@@ -3329,6 +3568,11 @@ sub kea_normalize_mac
     return lc($mac);
 }
 
+sub kea_normalize_mac
+{
+    return normalize_mac(shift);
+}
+
 sub kea_node_reservations6
 {
     my ( $backend, $config, $node ) = @_;
diff --git a/xCAT-test/unit/dhcp_infiniband_twin.t b/xCAT-test/unit/dhcp_infiniband_twin.t
new file mode 100644
index 000000000..ea4d79e8a
--- /dev/null
+++ b/xCAT-test/unit/dhcp_infiniband_twin.t
@@ -0,0 +1,343 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use lib "$FindBin::Bin/../../xCAT-server/lib";
+use lib "$FindBin::Bin/../../xCAT-server/lib/perl";
+use lib "$FindBin::Bin/../../perl-xCAT";
+
+use Test::More;
+
+$ENV{XCATCFG} ||= 'SQLite:/tmp';
+
+my $source_dhcp_plugin = "$FindBin::Bin/../../xCAT-server/lib/xcat/plugins/dhcp.pm";
+if ( -f $source_dhcp_plugin ) {
+    require $source_dhcp_plugin;
+} else {
+    require xCAT_plugin::dhcp;
+}
+
+sub twin { return xCAT_plugin::dhcp::_infiniband_twin_mac( $_[0] ); }
+
+is(
+    xCAT_plugin::dhcp::normalize_mac('B8-3F-D2-4A-68-AA'),
+    'b8:3f:d2:4a:68:aa',
+    'the shared MAC normalizer canonicalizes case and separators',
+);
+is( twin('b8:3f:d2:4a:68:aa'), 'b8:3f:d2:03:00:4a:68:aa',
+    'the port GUID of the first adapter is derived from its mac' );
+is( twin('b8:3f:d2:4a:68:b2'), 'b8:3f:d2:03:00:4a:68:b2',
+    'the port GUID of the second adapter is derived from its mac' );
+is( twin('b8-3f-d2-4a-68-aa'), 'b8:3f:d2:03:00:4a:68:aa',
+    'a dash-separated mac produces a canonical InfiniBand identity' );
+is( length( twin('b8:3f:d2:4a:68:aa') ), 23,
+    'the derived address is eight bytes' );
+
+foreach my $other ( 'b8:3f:d2:03:00:4a:68:aa', '00:11:22:33:44', '', 'notamac' ) {
+    is( twin($other), undef, "'$other' gives no derived address" );
+}
+is( twin(undef), undef, 'no mac gives no derived address' );
+ok(
+    xCAT_plugin::dhcp::_infiniband_identity_present(
+        'b8:3f:d2:4a:68:aa!node01',
+        'b8:3f:d2:03:00:4a:68:aa!node01-ib',
+    ),
+    'an explicit InfiniBand identity is detected in a node mac list',
+);
+ok(
+    !xCAT_plugin::dhcp::_infiniband_identity_present(
+        'b83fd203004a68aa!node01-ib',
+    ),
+    'a colonless address rejected by addnode is not treated as an identity',
+);
+ok(
+    xCAT_plugin::dhcp::_infiniband_identity_present(
+        'b8-3f-d2-03-00-4a-68-aa!node01-ib',
+    ),
+    'a valid dashed InfiniBand identity is detected in a node mac list',
+);
+ok(
+    !xCAT_plugin::dhcp::_infiniband_identity_present(
+        'b8:3f:d2:4a:68:aa!node01',
+    ),
+    'an Ethernet-only mac list needs the derived identity',
+);
+is(
+    xCAT_plugin::dhcp::_hardware_type_for('b8:3f:d2:4a:68:aa', 'eth0'),
+    1,
+    'an Ethernet interface uses the Ethernet hardware type',
+);
+is(
+    xCAT_plugin::dhcp::_hardware_type_for(
+        'b8:3f:d2:03:00:4a:68:aa', 'ib0'
+    ),
+    32,
+    'an eight-byte fabric address uses the InfiniBand hardware type',
+);
+is(
+    xCAT_plugin::dhcp::_hardware_type_for('b8:3f:d2:4a:68:aa', 'hf0'),
+    37,
+    'an HFI interface uses the HFI hardware type',
+);
+
+is(
+    xCAT_plugin::dhcp::_node_host_statements('node01', ''),
+    'ddns-hostname \"node01\"; send host-name \"node01\";',
+    'the default host statements identify the node',
+);
+is(
+    xCAT_plugin::dhcp::_node_host_statements(
+        'node01', 'filename = \"bootfile\";'
+    ),
+    'ddns-hostname \"node01\"; send host-name \"node01\";filename = \"bootfile\";',
+    'node identity is prepended to existing host statements',
+);
+is(
+    xCAT_plugin::dhcp::_noip_hostname('node01', 'B8:3F:D2:4A:68:AA'),
+    'node01-noipB83FD24A68AA',
+    'the denied-host name preserves the legacy MAC case',
+);
+is(
+    xCAT_plugin::dhcp::_noip_hostname('node01', 'B8-3F-D2-4A-68-AA'),
+    'node01-noipB8-3F-D2-4A-68-AA',
+    'the denied-host name preserves legacy dash separators',
+);
+
+my $create_commands = <<'OMAPI';
+new host
+set name = "node01-xcat-ib"
+open
+remove
+close
+new host
+set name = "node01-xcat-ib"
+set hardware-address = b8:3f:d2:03:00:4a:68:aa
+set dhcp-client-identifier = b8:3f:d2:03:00:4a:68:aa
+set hardware-type = 32
+set ip-address = 192.0.2.10
+set statements = "ddns-hostname \"node01\"; send host-name \"node01\";"
+create
+close
+OMAPI
+
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+        'ddns-hostname \"node01\"; send host-name \"node01\";', 1, 0
+    ),
+    $create_commands,
+    'an Ethernet identity on an IPoIB network creates the InfiniBand twin',
+);
+
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, '!service!ib0', '192.0.2.10',
+        'ddns-hostname \"node01\"; send host-name \"node01\";', 1, 0
+    ),
+    $create_commands,
+    'a relayed IPoIB interface creates the InfiniBand twin',
+);
+
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', 'DENIED', '', 1, 0
+    ),
+    join( '', ( split( /^/m, $create_commands ) )[ 0 .. 9 ] )
+      . "set statements = \"deny booting;\"\ncreate\nclose\n",
+    'a denied Ethernet identity creates a denied InfiniBand twin',
+);
+
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 32, 'ib0', '192.0.2.10', '', 1, 1
+    ),
+    undef,
+    'an existing InfiniBand identity does not create another twin',
+);
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'eth0', '192.0.2.10', '', 1, 0
+    ),
+    undef,
+    'an Ethernet network does not create an InfiniBand twin',
+);
+
+my $create_without_cleanup = <<'OMAPI';
+new host
+set name = "node01-xcat-ib"
+set hardware-address = b8:3f:d2:03:00:4a:68:aa
+set dhcp-client-identifier = b8:3f:d2:03:00:4a:68:aa
+set hardware-type = 32
+set ip-address = 192.0.2.10
+set statements = "ddns-hostname \"node01\"; send host-name \"node01\";"
+create
+close
+OMAPI
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+        'ddns-hostname \"node01\"; send host-name \"node01\";', 0, 0
+    ),
+    $create_without_cleanup,
+    'the Ubuntu-limited OMAPI path creates the twin without a failed-open cleanup',
+);
+my $create_without_address = $create_without_cleanup;
+$create_without_address =~ s/^set ip-address = .*\n//m;
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', undef,
+        'ddns-hostname \"node01\"; send host-name \"node01\";', 0, 0
+    ),
+    $create_without_address,
+    'an unresolved IP omits only the twin address',
+);
+is(
+    xCAT_plugin::dhcp::_infiniband_twin_create_commands(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10', '', 1, 1
+    ),
+    undef,
+    'an explicit InfiniBand identity suppresses the derived twin',
+);
+
+is_deeply(
+    [ xCAT_plugin::dhcp::_infiniband_twin_static_lines(
+        'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+        'option host-name "node01";', 0
+    ) ],
+    [
+        "host node01-xcat-ib {\n",
+        "    hardware infiniband b8:3f:d2:03:00:4a:68:aa;\n",
+        "    fixed-address 192.0.2.10;\n",
+        "    option host-name \"node01\";\n",
+        "}\n",
+    ],
+    'the static-host fallback declares the derived InfiniBand identity',
+);
+
+my $delete_name_commands = <<'OMAPI';
+new host
+set name = "node01-xcat-ib"
+open
+remove
+close
+OMAPI
+my $delete_address_commands = <<'OMAPI';
+new host
+set hardware-address = b8:3f:d2:03:00:4a:68:aa
+set hardware-type = 32
+open
+remove
+close
+OMAPI
+
+is(
+    xCAT_plugin::dhcp::_hardware_address_delete_commands(
+        'b8:3f:d2:4a:68:aa', 1
+    ),
+    "new host\nset hardware-address = b8:3f:d2:4a:68:aa\nopen\nremove\nclose\n",
+    'Ethernet cleanup keeps the legacy hardware-address lookup',
+);
+is(
+    xCAT_plugin::dhcp::_hardware_address_delete_commands(
+        'b8:3f:d2:03:00:4a:68:aa', 32
+    ),
+    $delete_address_commands,
+    'InfiniBand cleanup includes its OMAPI hardware type',
+);
+
+my @delete_commands = xCAT_plugin::dhcp::_infiniband_twin_delete_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', 1, 0
+);
+is_deeply(
+    \@delete_commands,
+    [ $delete_name_commands, $delete_address_commands ],
+    'removing a node produces separate name and address cleanup commands',
+);
+my @moved_network_delete_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_delete_commands(
+    'node01', 'b8-3f-d2-4a-68-aa', 1, 'eth0', 1, 1
+  );
+is_deeply(
+    \@moved_network_delete_commands,
+    [ $delete_name_commands, undef ],
+    'removing a moved node cleans up its old twin by name only',
+);
+my @limited_delete_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_delete_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', 0, 0
+  );
+is_deeply(
+    \@limited_delete_commands,
+    [ $delete_name_commands, undef ],
+    'the Ubuntu-limited OMAPI path still removes the twin by name',
+);
+my @limited_ethernet_delete_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_delete_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'eth0', 0, 0
+  );
+is_deeply(
+    \@limited_ethernet_delete_commands,
+    [],
+    'the Ubuntu-limited OMAPI path avoids a failed-open cleanup on Ethernet',
+);
+
+my @moved_network_update_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_update_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'eth0', '192.0.2.10',
+    'ddns-hostname \"node01\"; send host-name \"node01\";', 1, 0
+  );
+is_deeply(
+    \@moved_network_update_commands,
+    [ $delete_name_commands, undef, undef ],
+    're-registering a node on Ethernet removes its former twin by name only',
+);
+
+my @infiniband_update_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_update_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+    'ddns-hostname \"node01\"; send host-name \"node01\";', 1, 0
+  );
+is_deeply(
+    \@infiniband_update_commands,
+    [ $delete_name_commands, $delete_address_commands, $create_without_cleanup ],
+    're-registering an IPoIB node replaces its generated twin',
+);
+
+my @limited_update_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_update_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+    'ddns-hostname \"node01\"; send host-name \"node01\";', 0, 0
+  );
+is_deeply(
+    \@limited_update_commands,
+    [ undef, undef, $create_without_cleanup ],
+    'the limited OMAPI path does not attempt a failed-open cleanup',
+);
+
+my @explicit_identity_update_commands =
+  xCAT_plugin::dhcp::_infiniband_twin_update_commands(
+    'node01', 'b8:3f:d2:4a:68:aa', 1, 'ib0', '192.0.2.10',
+    'ddns-hostname \"node01\"; send host-name \"node01\";', 1, 1
+  );
+is_deeply(
+    \@explicit_identity_update_commands,
+    [ $delete_name_commands, undef, undef ],
+    'updating an explicit InfiniBand identity does not remove it by address',
+);
+
+# The mgtifname of a network can name more than one interface, separated by !.
+# The InfiniBand interface is not always the last one, so a test that only
+# matches the last name leaves a node on ib0!eth0 without its second entry.
+foreach my $ifname (qw(ib0 ib0.8001 eth0!ib0 ib0!eth0 ib0!ib1 bond0!ib2)) {
+    ok( xCAT_plugin::dhcp::_is_infiniband_interface($ifname),
+        "'$ifname' is served by an InfiniBand interface" );
+}
+foreach my $ifname (qw(eth0 eth0!eth1 bond0 hf0)) {
+    ok( !xCAT_plugin::dhcp::_is_infiniband_interface($ifname),
+        "'$ifname' is not served by an InfiniBand interface" );
+}
+ok( !xCAT_plugin::dhcp::_is_infiniband_interface(undef),
+    'a network with no interface name is not served by InfiniBand' );
+
+done_testing();
diff --git a/xCAT-test/unit/dhcp_static_host_markers.t b/xCAT-test/unit/dhcp_static_host_markers.t
new file mode 100644
index 000000000..8409a1965
--- /dev/null
+++ b/xCAT-test/unit/dhcp_static_host_markers.t
@@ -0,0 +1,184 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+use FindBin;
+use lib "$FindBin::Bin/../../xCAT-server/lib";
+use lib "$FindBin::Bin/../../xCAT-server/lib/perl";
+use lib "$FindBin::Bin/../../perl-xCAT";
+
+use Test::More;
+
+$ENV{XCATCFG} ||= 'SQLite:/tmp';
+
+my $source_dhcp_plugin = "$FindBin::Bin/../../xCAT-server/lib/xcat/plugins/dhcp.pm";
+if ( -f $source_dhcp_plugin ) {
+    require $source_dhcp_plugin;
+} else {
+    require xCAT_plugin::dhcp;
+}
+
+my @config;
+
+my @infiniband_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node00', 'node00', 'b8:3f:d2:03:00:4a:68:aa', 32,
+    'ib0', '192.0.2.10', '', 1, \@infiniband_config,
+);
+like(
+    join( '', @infiniband_config ),
+    qr/^\s*hardware infiniband b8:3f:d2:03:00:4a:68:aa;$/m,
+    'the static-host fallback keeps an explicit InfiniBand hardware type',
+);
+unlike(
+    join( '', @infiniband_config ),
+    qr/^\s*hardware ethernet b8:3f:d2:03:00:4a:68:aa;$/m,
+    'the static-host fallback does not label an InfiniBand identity as Ethernet',
+);
+
+my @dashed_mac_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node00', 'node00', 'B8-3F-D2-4A-68-AA', 1,
+    'eth0', '192.0.2.11', '', 0, \@dashed_mac_config,
+);
+like(
+    join( '', @dashed_mac_config ),
+    qr/^\s*hardware ethernet b8:3f:d2:4a:68:aa;$/m,
+    'the static-host fallback emits a valid canonical dashed MAC',
+);
+
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node01', 'node01', '00:11:22:33:44:55', 1,
+    'eth0', '192.0.2.1', '', 0, \@config,
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node02', 'node02', '00:11:22:33:44:66', 1,
+    'eth0', '192.0.2.2', '', 0, \@config,
+);
+
+like(
+    join( '', @config ),
+    qr/^#xCAT host declaration for node01 aka host node01 end$/m,
+    'the static host end marker occupies its own line',
+);
+
+xCAT_plugin::dhcp::_delete_isc_static_host('node01', \@config);
+my $remaining = join( '', @config );
+unlike($remaining, qr/\bnode01\b/, 'the selected static host is removed');
+like($remaining, qr/\bnode02\b/, 'the following static host is preserved');
+
+my @legacy_config = (
+    "#xCAT host declaration for node01 aka host node01 start\n",
+    "host node01 {\n",
+    "    hardware ethernet 00:11:22:33:44:55;\n",
+    "    fixed-address 192.0.2.1;\n",
+    "} #xCAT host declaration for node01 aka host node01 end\n",
+    "#xCAT host declaration for node02 aka host node02 start\n",
+    "host node02 {\n",
+    "    hardware ethernet 00:11:22:33:44:66;\n",
+    "    fixed-address 192.0.2.2;\n",
+    "} #xCAT host declaration for node02 aka host node02 end\n",
+);
+xCAT_plugin::dhcp::_delete_isc_static_host('node01', \@legacy_config);
+my $legacy_remaining = join( '', @legacy_config );
+unlike($legacy_remaining, qr/\bnode01\b/,
+    'a static host written by an older xCAT release is removed');
+like($legacy_remaining, qr/\bnode02\b/,
+    'deleting an old-format host preserves the following host');
+
+my @multi_host_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node03', 'node03', '00:11:22:33:44:77', 1,
+    'eth0', '192.0.2.3', '', 0, \@multi_host_config,
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node03', 'node03-ib', '00:11:22:33:44:88', 32,
+    'ib0', '192.0.2.3', '', 1, \@multi_host_config,
+);
+my $multi_host = join( '', @multi_host_config );
+like($multi_host, qr/^host node03 \{$/m,
+    'adding a second identity preserves the first host for a node');
+like($multi_host, qr/^host node03-ib \{$/m,
+    'adding a second identity records its own host for the node');
+
+my @prefix_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node01', 'node01', '00:11:22:33:44:99', 1,
+    'eth0', '192.0.2.1', '', 0, \@prefix_config,
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node01-ib', 'node01-ib', '00:11:22:33:44:aa', 1,
+    'eth0', '192.0.2.4', '', 0, \@prefix_config,
+);
+xCAT_plugin::dhcp::_delete_isc_static_host('node01', \@prefix_config);
+my $prefix_remaining = join( '', @prefix_config );
+unlike($prefix_remaining, qr/^host node01 \{$/m,
+    'node-wide deletion removes the exact node');
+like($prefix_remaining, qr/^host node01-ib \{$/m,
+    'node-wide deletion preserves a node with the same prefix');
+
+my @replacement_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node04', 'node04-old', '00:11:22:33:44:bb', 1,
+    'eth0', '192.0.2.5', '', 0, \@replacement_config,
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node04', 'node04-old-ib', '00:11:22:33:44:cc', 32,
+    'ib0', '192.0.2.5', '', 1, \@replacement_config,
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node05', 'node05', '00:11:22:33:44:dd', 1,
+    'eth0', '192.0.2.6', '', 0, \@replacement_config,
+);
+ok(
+    xCAT_plugin::dhcp::_begin_isc_static_host_update(
+        'node04', 1, \@replacement_config,
+    ),
+    'removing stale identities marks the static configuration as changed',
+);
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node04', 'node04-current', '00:11:22:33:44:ee', 1,
+    'eth0', '192.0.2.5', '', 0, \@replacement_config,
+);
+my $replacement = join( '', @replacement_config );
+unlike($replacement, qr/^host node04-old(?:-ib)? \{$/m,
+    're-registering a node removes identities that are no longer present');
+like($replacement, qr/^host node04-current \{$/m,
+    're-registering a node writes its current identity');
+like($replacement, qr/^host node05 \{$/m,
+    're-registering a node preserves other nodes');
+ok(
+    !xCAT_plugin::dhcp::_begin_isc_static_host_update(
+        'node04', 0, \@replacement_config,
+    ),
+    'a disabled static update leaves the configuration unchanged',
+);
+
+my @lazy_config;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node06', 'node06-old', '00:11:22:33:44:11', 1,
+    'eth0', '192.0.2.7', '', 0, \@lazy_config,
+);
+my $before_failed_update = join( '', @lazy_config );
+my $update_started = 0;
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node06', 'node06-current', '00:11:22:33:44:22', 1,
+    'eth0', undef, '', 0, \@lazy_config, \$update_started,
+);
+is(join( '', @lazy_config ), $before_failed_update,
+    'an unresolved replacement preserves the existing static host');
+is($update_started, 0,
+    'an unresolved replacement does not begin the static update');
+xCAT_plugin::dhcp::_add_isc_static_host(
+    'node06', 'node06-current', '00:11:22:33:44:22', 1,
+    'eth0', '192.0.2.8', '', 0, \@lazy_config, \$update_started,
+);
+my $lazy_replacement = join( '', @lazy_config );
+unlike($lazy_replacement, qr/^host node06-old \{$/m,
+    'the first valid replacement removes stale node identities');
+like($lazy_replacement, qr/^host node06-current \{$/m,
+    'the first valid replacement writes the current identity');
+is($update_started, 1,
+    'the successful replacement records that cleanup has started');
+
+done_testing();