--- /opt/sbin/munin-node.orig   2013-01-27 15:13:51.869007214 +0100
+++ /opt/sbin/munin-node 2013-01-27 16:11:20.536006950 +0100
@@ -133,7 +133,7 @@
   if [ -n "$(which ethtool)" ]; then
  if [ -x "$(which ethtool)" ]; then
          if ethtool $1 | grep -q Speed; then
-                MAX=$(($(ethtool $1 | grep Speed | sed -e 's/[[:space:]]\{1,\}/ /g' -e 's/^ //' -e 's/M.*//' | cut -d\  -f2) * 1000000))
+                MAX=$(($(ethtool $1 | grep Speed | sed -e 's/[[:space:]]\{1,\}/ /g' -e 's/^ //' -e 's/M.*//' | sed -e 's/Unknown\!/0/' | cut -d\  -f2) * 1000000))
              echo "up.max $MAX"
              echo "down.max $MAX"
      fi
@@ -535,19 +535,31 @@
     for INTER in $(grep '^ *\(ppp\|eth\|wlan\|ath\|ra\|ipsec\|tap\|br-\)\([^:]\)\{1,\}:' /proc/net/dev | cut -f1 -d: | sed 's/ //g
 s/\-/_/g');
     do
-      INTERRES=$(echo $INTER | sed 's/\./VLAN/')
-      RES="$RES if_$INTERRES"
-      eval "fetch_if_${INTERRES}() { fetch_if $INTER $@; };"
-      eval "config_if_${INTERRES}() { config_if $INTER $@; };"
+      if [ -n "$(which ethtool)" ]; then
+        if [ -x "$(which ethtool)" ]; then
+          if [ -n "$(ethtool $INTER | grep 'Link detected: yes')" ]; then
+            INTERRES=$(echo $INTER | sed 's/\./VLAN/')
+            RES="$RES if_$INTERRES"
+            eval "fetch_if_${INTERRES}() { fetch_if $INTER $@; };"
+            eval "config_if_${INTERRES}() { config_if $INTER $@; };"
+          fi
+        fi
+      fi
     done
   elif [ "$PLUG" = "if_err_" ]; then
     for INTER in $(grep '^ *\(ppp\|eth\|wlan\|ath\|ra\|ipsec\|tap\|br-\)\([^:]\)\{1,\}:' /proc/net/dev | cut -f1 -d: | sed 's/ //g
 s/\-/_/g');
     do
-      INTERRES=$(echo $INTER | sed 's/\./VLAN/')
-      RES="$RES if_err_$INTERRES"
-      eval "fetch_if_err_${INTERRES}() { fetch_if_err $INTER $@; };"
-      eval "config_if_err_${INTERRES}() { config_if_err $INTER $@; };"
+      if [ -n "$(which ethtool)" ]; then
+        if [ -x "$(which ethtool)" ]; then
+          if [ -n "$(ethtool $INTER | grep 'Link detected: yes')" ]; then
+            INTERRES=$(echo $INTER | sed 's/\./VLAN/')
+            RES="$RES if_err_$INTERRES"
+            eval "fetch_if_err_${INTERRES}() { fetch_if_err $INTER $@; };"
+            eval "config_if_err_${INTERRES}() { config_if_err $INTER $@; };"
+          fi
+        fi
+      fi
     done
   elif [ "$PLUG" = "netstat" ]; then
     if netstat -s >/dev/null 2>&1; then