[squid-users] the sibling cache peer can't work. help!

I use 121.9.*.77 and 121.9.*.78 as sibling cache peer
when i see server_list in cachemgr, there has no fetches from it's cache peer.
what is wrong with my configure file?

htcp 4827
cache_peer 121.9.*.78 sibling 80 4827 proxy-only htcp

acl All src 0/0
htcp_access allow All

Sibling : 121.9.*.78
Host : 121.9.*.78/80/4827
Flags : proxy-only htcp
Address[0] : 121.9.233.78
Status : Up

AVG RTT : 0 msec
OPEN CONNS : 0
LAST QUERY : 1205908950 seconds ago
LAST REPLY : none received
PINGS SENT : 0
PINGS ACKED: 0 0%
FETCHES : 0 0%
IGNORED : 0 0%

Histogram of PINGS ACKED:
        Misses 0 0%
        Hits 0 0%
keep-alive ratio: 0%
Received on Wed Mar 19 2008 - 01:08:00 MDT