diff --git a/plugins/dynamix/Eth0.page b/plugins/dynamix/Eth0.page
index 2a8c1762f..e449f167f 100644
--- a/plugins/dynamix/Eth0.page
+++ b/plugins/dynamix/Eth0.page
@@ -681,7 +681,7 @@ IPv6 DNS server 3:
 </div>
 </div>
 Desired MTU:
-: <input type="number" name="MTU" min="68" max="9198" value="<?=$eth0['MTU']?>" class="narrow" placeholder="1500">
+: <input type="number" name="MTU" min="68" max="9198" value="<?=$eth0['MTU']?>" class="narrow" placeholder="<?=exec("ip link show dev eth0|grep -Pom1 'mtu \K\d+'")?>">
 
 > This is the MTU size to use on the physical Ethernet interface.
 > If left blank, the MTU will automatically be determined (by default 1500 bytes).
diff --git a/plugins/dynamix/EthX.page b/plugins/dynamix/EthX.page
index 171cc2078..f83fe48e7 100644
--- a/plugins/dynamix/EthX.page
+++ b/plugins/dynamix/EthX.page
@@ -291,7 +291,7 @@ IPv6 privacy extensions:
 </div>
 </div>
 Desired MTU:
-: <input type="number" name="MTU" min="68" max="9198" value="<?=$locked?$ethX['MTU']:$ethX['MTU']?>" class="narrow" placeholder="1500">
+: <input type="number" name="MTU" min="68" max="9198" value="<?=$locked?$ethX['MTU']:$ethX['MTU']?>" class="narrow" placeholder="<?=exec("ip link show dev ethX|grep -Pom1 'mtu \K\d+'")?>">
 
 > This is the MTU size to use on the physical Ethernet interface.
 > If left blank, the MTU will automatically be determined (by default 1500 bytes).