diff --git a/ipam/allocate.go b/ipam/allocate.go
index fbc3a685..c144edfd 100644
--- a/ipam/allocate.go
+++ b/ipam/allocate.go
@@ -33,7 +33,7 @@ func (g *allocate) Try(alloc *Allocator) bool {
 		return true
 	}
 
-	if !alloc.universe.Overlaps(g.r.Range()) {
+	if !alloc.universe.Range().Overlaps(g.r.Range()) {
 		g.resultChan <- allocateResult{err: fmt.Errorf("range %s out of bounds: %s", g.r, alloc.universe)}
 		return true
 	}
diff --git a/ipam/allocator.go b/ipam/allocator.go
index 1adec91e..50950ffe 100644
--- a/ipam/allocator.go
+++ b/ipam/allocator.go
@@ -55,7 +55,7 @@ type Allocator struct {
 	stopChan          chan<- struct{}
 	ourName           mesh.PeerName
 	seed              []mesh.PeerName          // optional user supplied ring seed
-	universe          address.Range            // superset of all ranges
+	universe          address.CIDR             // superset of all ranges
 	ring              *ring.Ring               // information on ranges owned by all peers
 	space             space.Space              // more detail on ranges owned by us
 	owned             map[string]ownedData     // who owns what addresses, indexed by container-ID
@@ -80,7 +80,7 @@ type Config struct {
 	OurUID      mesh.PeerUID
 	OurNickname string
 	Seed        []mesh.PeerName
-	Universe    address.Range
+	Universe    address.CIDR
 	IsObserver  bool
 	Quorum      func() uint
 	Db          db.DB
@@ -101,7 +101,7 @@ func NewAllocator(config Config) *Allocator {
 		ourName:     config.OurName,
 		seed:        config.Seed,
 		universe:    config.Universe,
-		ring:        ring.New(config.Universe.Start, config.Universe.End, config.OurName),
+		ring:        ring.New(config.Universe.Range().Start, config.Universe.Range().End, config.OurName),
 		owned:       make(map[string]ownedData),
 		db:          config.Db,
 		paxos:       participant,
@@ -953,7 +953,7 @@ func (alloc *Allocator) loadPersistedData() bool {
 		return false
 	}
 
-	if persistedRing.Range() != alloc.universe {
+	if persistedRing.Range() != alloc.universe.Range() {
 		overwritePersisted("Deleting persisted data for IPAM range %s; our range is %s", persistedRing.Range(), alloc.universe)
 		return false
 	}
diff --git a/ipam/claim.go b/ipam/claim.go
index 6ad1b712..fda36f15 100644
--- a/ipam/claim.go
+++ b/ipam/claim.go
@@ -58,7 +58,7 @@ func (c *claim) Try(alloc *Allocator) bool {
 	case mesh.UnknownPeerName:
 		// If our ring doesn't know, it must be empty.
 		alloc.infof("Claim %s for %s: is in the range %s, but the allocator is not initialized yet; will try later.",
-			c.cidr, c.ident, alloc.universe.AsCIDRString())
+			c.cidr, c.ident, alloc.universe)
 		if c.noErrorOnUnknown {
 			c.sendResult(nil)
 		}
diff --git a/ipam/testutils_test.go b/ipam/testutils_test.go
index b665771b..13fa8171 100644
--- a/ipam/testutils_test.go
+++ b/ipam/testutils_test.go
@@ -143,7 +143,7 @@ func makeAllocator(name string, cidrStr string, quorum uint) (*Allocator, addres
 		OurName:     peername,
 		OurUID:      mesh.PeerUID(rand.Int63()),
 		OurNickname: "nick-" + name,
-		Universe:    cidr.Range(),
+		Universe:    cidr,
 		IsObserver:  quorum == 0,
 		Quorum:      func() uint { return quorum },
 		Db:          new(mockDB),
diff --git a/prog/weaver/main.go b/prog/weaver/main.go
index f1d895fd..e185abde 100644
--- a/prog/weaver/main.go
+++ b/prog/weaver/main.go
@@ -427,7 +427,7 @@ func createAllocator(router *weave.NetworkRouter, config ipamConfig, db db.DB, i
 		OurUID:      router.Ourself.Peer.UID,
 		OurNickname: router.Ourself.Peer.NickName,
 		Seed:        config.SeedPeerNames,
-		Universe:    ipRange.Range(),
+		Universe:    ipRange,
 		IsObserver:  config.Observer,
 		Quorum:      func() uint { return determineQuorum(config.PeerCount, router) },
 		Db:          db,