Help! Whats up with my network?!

I've just done a simple nmap scan of my network with nmap: nmap -sP 192.168.1.1-255

networkserver@networkServer:~$ sudo nmap -sP 192.168.1.1-255

Starting Nmap 5.00 ( http://nmap.org ) at 2010-08-26 17:46 NZST
Host RTA1320.home (192.168.1.1) is up (0.00060s latency).
MAC Address: 00:26:B6:C9:E7:48 (Unknown)
Host 192.168.1.2 is up (0.00057s latency).
MAC Address: 00:23:69:16:85:D7 (Cisco-Linksys)
Host 192.168.1.3 is up (0.00015s latency).
MAC Address: 02:27:19:B4:61:DB (Unknown)
Host networkServer (192.168.1.50) is up.
Host 192.168.1.104 is up (0.0012s latency).
MAC Address: 00:1A:4D:9C:70:0E (Giga-byte Technology Co.)
Host 192.168.1.109 is up (0.0076s latency).
MAC Address: 78:E4:00:8E:FE:63 (Unknown)
Nmap done: 255 IP addresses (6 hosts up) scanned in 28.74 seconds

That seemed to take a rather long time, so I check with a friend on his network and it only took 2.74 secconds!

My network layout is:

                             /---WifiRouter----#laptop>
Modem----server---switch---->
                             \---#devbox

I figure something is wrong with the routing settings on my network but I'm not sure how to check it? Any ideas?

From serverfault glisignoli

• Could you give the output of command (on the server): # route -n ?

  glisignoli : Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 100 0 0 eth0
  From sentinel

• The network you checked was the same ? Machines / Os / topology. Also, do you (or he) have/has QOS enabled on your / his switch ?

  Also it would be helpful it you give the Ip's of every machine. (to know what is what). Just to mention that it seems that your bottleneck is located on 192.168.1.104 (Giga-byte Technology Co.). What is it ?

  From Nikolaidis Fotis