diff --git a/filter_plugins/cumulus.py b/filter_plugins/cumulus.py
index 7186cd9..72386e1 100644
--- a/filter_plugins/cumulus.py
+++ b/filter_plugins/cumulus.py
@@ -34,19 +34,21 @@ class FilterModule(object):
         '''
         Generate a clag-id from a list of interfaces making up a MLAG bond
 
-        The clag-id for a bond must be between 1 and 65535. Generate it by
-        combining the indexes of the lowest-numbered interface on each switch.
-        This avoids manual ID assignment while keeping them mostly stable.
-
-        This clag-id does not change unless the lowest-numbered interface for
-        the bond on any switch changes. IDs of other bonds are not affected.
+        Interfaces on both sides must be the same. The clag-id is generated
+        from the interface name such as:
+          swp3 -> 3
+          swpX -> X
+          swpXsY -> X0Y
+        This may fail on very large switches with more than 1000 ports.
         '''
         clag_id = 0
         key = lambda i: i.get('device', {}).get('name')
-        for device, ifaces in itertools.groupby(sorted(interfaces, key=key), key):
-            clag_id = 256 * clag_id + min(self.cl_iface_index(ifaces))
-        if 1 <= clag_id <= 65535: # sanity checking
-            return clag_id
+        proto_iface = sorted(interfaces, key=key)[0]
+        g = re.match(r"[^0-9]*([0-9]+)(s([0-9]+))?", proto_iface["name"]).groups()
+        clag_id = g[0]
+        if g[2] is not None:
+            clag_id += '0' + g[2]
+        return clag_id
 
     def cl_clag_sys_mac(self, address):
         '''Generate a system MAC address for a MLAG with the given address'''