diff --git a/sys/include/ip.h b/sys/include/ip.h
index 56e707729..c2ab8dcf8 100644
--- a/sys/include/ip.h
+++ b/sys/include/ip.h
@@ -161,9 +161,9 @@ void	maskip(uchar*, uchar*, uchar*);
 int	eipfmt(Fmt*);
 int	isv4(uchar*);
 vlong	parseip(uchar*, char*);
-vlong	parseipmask(uchar*, char*);
+vlong	parseipmask(uchar*, char*, int);
+vlong	parseipandmask(uchar*, uchar*, char*, char*);
 char*	v4parseip(uchar*, char*);
-char*	v4parsecidr(uchar*, uchar*, char*);
 int	parseether(uchar*, char*);
 int	myipaddr(uchar*, char*);
 int	myetheraddr(uchar*, char*);
diff --git a/sys/man/2/ip b/sys/man/2/ip
index e84b14c08..d2fcab0dd 100644
--- a/sys/man/2/ip
+++ b/sys/man/2/ip
@@ -1,6 +1,6 @@
 .TH IP 2
 .SH NAME
-eipfmt, parseip, parseipmask, v4parseip, v4parsecidr, parseether, myipaddr, myetheraddr, maskip, equivip4, equivip6, defmask, isv4, v4tov6, v6tov4, nhgetv, nhgetl, nhgets, hnputv, hnputl, hnputs, ptclbsum, readipifc \- Internet Protocol addressing
+eipfmt, parseip, parseipmask, parseipandmask, v4parseip, parseether, myipaddr, myetheraddr, maskip, equivip4, equivip6, defmask, isv4, v4tov6, v6tov4, nhgetv, nhgetl, nhgets, hnputv, hnputl, hnputs, ptclbsum, readipifc \- Internet Protocol addressing
 .SH SYNOPSIS
 .B #include <u.h>
 .br
@@ -15,15 +15,15 @@ int	eipfmt(Fmt*)
 vlong	parseip(uchar *ipaddr, char *str)
 .PP
 .B
-vlong	parseipmask(uchar *ipaddr, char *str)
+vlong	parseipmask(uchar *ipaddr, char *str, int v4)
+.PP
+.B
+vlong	parseipandmask(uchar *ipaddr, uchar *ipmask, char *ipstr, char *maskstr)
 .PP
 .B
 char*	v4parseip(uchar *ipaddr, char *str)
 .PP
 .B
-ulong	v4parsecidr(uchar *addr, uchar *mask, char *str)
-.PP
-.B
 int	parseether(uchar *eaddr, char *str)
 .PP
 .B
@@ -152,13 +152,37 @@ As a concession to backwards compatibility,
 if the string is a V4 address, the return value
 is an unsigned long integer containing the big-endian V4 address.
 If not, the return value is 6.
+.PP
 .I Parseipmask
 converts a string pointed to by
 .I str
-to a 6-byte IP mask starting at
+to a 16-byte IP mask starting at
 .IR ipaddr .
 It too returns an unsigned long big-endian V4 address or 6.
-Both routines return -1 on errors.
+.I Parseipmask
+accepts a mask in
+.BI / prefixlen
+slash notation. When the
+.IR v4
+argument is non-zero, then
+.I prefixlen
+in range [0..32] is offset by 96 to yield a mask for a V4 address.
+.PP
+.I Parseipandmask
+combines
+.I parseip
+and
+.I parseipmask
+into a single call, interpreting the mask in context of the
+supplied IP address type.
+The returned IP mask is
+.B /128
+when
+.I maskstr
+is
+.BR nil .
+.PP
+All three functions return -1 on errors.
 .PP
 .I V4parseip
 converts a string pointed to by
@@ -166,15 +190,6 @@ converts a string pointed to by
 to a 4-byte V4 IP address starting at
 .IR ipaddr .
 .PP
-.I V4parsecidr
-converts a string of the form
-addr/mask, pointed to by
-.IR str ,
-to a 4-byte V4 IP address starting at
-.I ipaddr
-and a 4-byte V4 IP mask starting at
-.IR mask .
-.PP
 .I Myipaddr
 returns the first valid IP address in
 the IP stack rooted at
@@ -207,7 +222,7 @@ operates on v6 addresses.
 .PP
 .I Defmask
 returns the standard class A, B, or C mask for
-.IR ipaddr .
+.I ipaddr .
 .PP
 .I Isv4
 returns non-zero if the V6 address is in the V4 space, that is,
diff --git a/sys/src/libip/parseip.c b/sys/src/libip/parseip.c
index 9f5d5dac7..757716770 100644
--- a/sys/src/libip/parseip.c
+++ b/sys/src/libip/parseip.c
@@ -122,7 +122,7 @@ parseip(uchar *to, char *from)
  *  style
  */
 vlong
-parseipmask(uchar *to, char *from)
+parseipmask(uchar *to, char *from, int v4)
 {
 	int i, w;
 	vlong x;
@@ -133,6 +133,8 @@ parseipmask(uchar *to, char *from)
 		i = atoi(from+1);
 		if(i < 0)
 			i = 0;
+		if(i <= 32 && v4)
+			i += 96;
 		if(i > 128)
 			i = 128;
 		w = i;
@@ -141,7 +143,6 @@ parseipmask(uchar *to, char *from)
 			*p++ = 0xff;
 		if(i > 0)
 			*p = ~((1<<(8-i))-1);
-		x = nhgetl(to+IPv4off);
 		/*
 		 * identify as ipv6 if the mask is inexpressible as a v4 mask
 		 * (because it has too few mask bits).  Arguably, we could
@@ -149,6 +150,7 @@ parseipmask(uchar *to, char *from)
 		 */
 		if (w < 8*(IPaddrlen-IPv4addrlen))
 			return 6;
+		x = nhgetl(to+IPv4off);
 	} else {
 		/* as a straight v4 bit mask */
 		x = parseip(to, from);
@@ -160,29 +162,15 @@ parseipmask(uchar *to, char *from)
 	return x;
 }
 
-/*
- *  parse a v4 ip address/mask in cidr format
- */
-char*
-v4parsecidr(uchar *addr, uchar *mask, char *from)
+vlong
+parseipandmask(uchar *ip, uchar *mask, char *ipstr, char *maskstr)
 {
-	int i;
-	char *p;
-	uchar *a;
+	vlong x;
 
-	p = v4parseip(addr, from);
-
-	if(*p == '/'){
-		/* as a number of prefix bits */
-		i = strtoul(p+1, &p, 0);
-		if(i > 32)
-			i = 32;
-		memset(mask, 0, IPv4addrlen);
-		for(a = mask; i >= 8; i -= 8)
-			*a++ = 0xff;
-		if(i > 0)
-			*a = ~((1<<(8-i))-1);
-	} else 
-		memcpy(mask, defmask(addr), IPv4addrlen);
-	return p;
+	x = parseip(ip, ipstr);
+	if(x == -1)
+		return -1;
+	if(maskstr == nil || parseipmask(mask, maskstr, memcmp(ip, v4prefix, IPv4off) == 0) == -1)
+		memset(mask, 0xff, IPaddrlen);
+	return x;
 }
diff --git a/sys/src/libip/readipifc.c b/sys/src/libip/readipifc.c
index 8169a14eb..70212ef57 100644
--- a/sys/src/libip/readipifc.c
+++ b/sys/src/libip/readipifc.c
@@ -31,9 +31,7 @@ _readoldipifc(char *buf, Ipifc **l, int index)
 		/* allocate new local address */
 		*ll = lifc = mallocz(sizeof(Iplifc), 1);
 		ll = &lifc->next;
-
-		parseip(lifc->ip, f[i]);
-		parseipmask(lifc->mask, f[i+1]);
+		parseipandmask(lifc->ip, lifc->mask, f[i], f[i+1]);
 		parseip(lifc->net, f[i+2]);
 		ifc->pktin = strtoul(f[i+3], nil, 10);
 		ifc->pktout = strtoul(f[i+4], nil, 10);
@@ -129,8 +127,7 @@ lose:
 		*ll = lifc = mallocz(sizeof(Iplifc), 1);
 		ll = &lifc->next;
 
-		parseip(lifc->ip, f[0]);
-		parseipmask(lifc->mask, f[1]);
+		parseipandmask(lifc->ip, lifc->mask, f[0], f[1]);
 		parseip(lifc->net, f[2]);
 
 		lifc->validlt = strtoul(f[3], nil, 10);