Loopback is currently broken in build 15760 and higher

iptables -t nat -I POSTROUTING -o br0 -s 192.168.123.0/24 -d 192.168.123.0/24 -j MASQUERADE

LAN=`nvram get lan_ipaddr`/`nvram get lan_netmask`
iptables -t nat -I POSTROUTING -o br0 -s $LAN -d $LAN -j MASQUERADE

Disable "Filter WAN NAT Redirection"

Chain POSTROUTING (policy ACCEPT 10 packets, 1026 bytes)
 pkts bytes target     prot opt in     out     source               destination
    5   464 SNAT       0    --  *      eth0    192.168.123.0/24     0.0.0.0/0           to:14.136.153.132
    0     0 RETURN     0    --  *      br0     0.0.0.0/0            0.0.0.0/0           PKTTYPE = broadcast

Enabling this filter will effectively disable local loopback.

Chain POSTROUTING (policy ACCEPT 8 packets, 632 bytes)
 pkts bytes target     prot opt in     out     source               destination
    8   752 SNAT       0    --  *      eth0    192.168.123.0/24     0.0.0.0/0           to:14.136.153.132
    0     0 DROP       0    --  *      br0     192.168.123.0/24     192.168.123.0/24

iptables -t nat -vnL PREROUTING
iptables -vnL FORWARD

Chain POSTROUTING (policy ACCEPT 1368 packets, 103K bytes)
 pkts bytes target     prot opt in     out     source               destination
    1   328 MASQUERADE 0    --  *      br0     192.168.123.0/24     192.168.123.0/24
  683 56635 SNAT       0    --  *      eth0    192.168.123.0/24     0.0.0.0/0           to:14.136.153.132
    0     0 RETURN     0    --  *      br0     0.0.0.0/0            0.0.0.0/0           PKTTYPE = broadcast

http://svn.dd-wrt.com:8000/ticket/1868