3 nics, 2 with same network/mask

I run openbsd with 3 NICs,
ep1 is dhcp, interface with internet ip addy
dc0 is 192.168.0.254/24
sis0 is 192.168.0.253/24

My system somehow lags, and some services do not work properly, i want to run a lot of local network services like samba, named, ftp, http, dhcpd, radiusd.
output of netstat -r :

Routing tables

Internet:
Destination Gateway Flags Refs Use Mtu Interface
default whatever.star UGS 7 8350141 - ep1
whatever1.star link#3 UC 1 0 - ep1
whatever3.star 0:f:90:27:e5:c9 UHLc 1 0 - ep1
whatever.st localhost.starman. UGHS 0 4 33224 lo0
loopback localhost.starman. UGRS 0 0 33224 lo0
localhost.starman. localhost.starman. UH 2 310 33224 lo0
192.168.0/24 link#1 UC 5 0 - dc0
1k 0:8:a1:25:95:cf UHLc 2 7146246 - L dc0
192.168.0.3 0:30:bd:f5:2:a8 UHLc 3 367525 - L dc0
192.168.0.4 0:50:bf:9a:9e:57 UHLc 2 425203 - dc0
2k 0:80:c8:93:8b:47 UHLc 1 2465467 - dc0
vinni 0:4:e2:1f:8:95 UHLc 0 11 - lo0
BASE-ADDRESS.MCAST localhost.starman. URS 0 0 33224 lo0

And i see that perfomance of machine is very strange,might some one tell me whats wrong?
sis0 192.168.0.253 is default gw for 192.168.0/24,and has QoS (altq)
ep1 also has QoS
dc0 must work on full speed in local network. But i still see server lagging.Someone told that wount theese ifaces in same network segment work, would be routing problems.
Is my configurations ok? and maybe you might advice me a better solution for my problem.

Thx.

okey, the solution was to make dc0 be in other network than sis0, i made it 192.168.1.1/24 and all started to work fine.