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Re: Enabling VNC



> What is MTU?  How do I ping with different sized packets?  What would 
> that tell me?
> > 
MTU is maximum transmission unit (packet size) in bytes that the
interface will transmit/recieve. 

If it is linux, run ifconfig and you will see the MTU value listed for
each interface:

eth1      Link encap:Ethernet  HWaddr 00:05:5D:6B:D6:BF
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4696 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3557 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:553921 (540.9 Kb)  TX bytes:2482084 (2.3 Mb)
          Interrupt:9 Base address:0xd800

Default ethernet MTU is 1500, but sometimes it gets altered along the
way up by the remote end OS or the physical mediums during transmission.

do a man on ping, but on linux it is:

ping -s <packetsize>

tcpdump -vvv host <host>

This will give an output somthing like:
12:59:43.482011 linhost.localdomain > 192.168.0.101: icmp: echo request
(DF) (ttl 64, id 14, len 1328)
12:59:43.482539 192.168.0.101 > linhost.localdomain: icmp: echo reply
(ttl 64, id 3650, len 1328)

where len =  packet size. To get this packet size I ran ping -s 1300
192.168.0.101.

This is a pretty informative article:
http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/mtu.html

There is some information in the iptables man pages - look for clamp or
TCPMSS.


> > Also check to make sure that VNC is actually listening on the port you
> > think it should be. You can netstat -npl to check for that.
> 
> I have done netstat and have found out that it is listening on the 
> right port (after fixing iptables).
> 
> Jeremy
> 
> > 
> 

ta, gb


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