[ILUG] Enabling server to access single IP address out of net mask range

[Burke, Gary : GIG IS&T]

Would it not be possible to add a second IP address to the box and allow
access to the foreign IP address from there...?

ie.  Your IP would be 192.168.200.1/24
Your other IP would be 192.168.205.x/24

Then you can access all the addresses on the 192.168.200 and 192.168.205
networks.


Let see:
In your kernel config, enable IP Aliasing.  Compile and reboot (This is
assuming it's not already on)
then use "ifconfig eth0:0 192.168.205.2 netmask 255.255.255.0 up"

This will give you an interface on the 192.168.205 network.  You will
probably have to do something like

route add -net 192.168.205.0 netmask 255.255.255.0 eth0:0


Gary

> -----Original Message-----
> From:	Cormac Hogan [SMTP:cormac_hogan at hotmail.com]
> Sent:	Thursday, June 08, 2000 2:28 PM
> To:	Tony.Patton at nwifhe.ac.uk
> Cc:	ilug at linux.ie
> Subject:	[ILUG] Enabling server to access single IP address out of
> netmask range
> 
> Date: Thu, 08 Jun 2000 06:27:49 PDT
> Mime-Version: 1.0
> Content-Type: text/plain; format=flowed
> 
> Tony,
> 
> With a netmask of 255.255.255.0, I believe that the only hosts which this 
> oracle server (192.168.200.1) can reach are from 192.168.200.1 - 
> 192.168.200.254. Therefore I'm confused as to how it can even reach the 
> router 192.168.1.1 as it will think that this is a different class C
> network 
> ?
> If the netmask was 255.255.0.0, then it wouldn't be a problem as the
> router 
> and host would be on the same class B network.
> 
> Alternatively, if you want this host to reach the 192.168.205 network, you
> 
> would need to set the netmask to 255.255.250.0. This will allow the oracle
> 
> server (192.168.200.1) to reach hosts in the address range 192.168.200.1 -
> 
> 192.168.205.254, i.e. your print server & associated routers.
> 
> If you now want wish to narrow this down further and only access a certain
> 
> range of hosts, this gets more tricky. Because of the way the netmask is 
> organised, if you wish to allow access to hosts from xx.xx.xx.60 to 
> xx.xx.xx.70, you will need to set the msbit of the lsbyte of the subnet 
> mask, i.e. 255.255.250.128. This will mask all hosts except hosts from 
> xx.xx.xx.1 - xx.xx.xx.126. However, this screws you since your print
> server 
> & router are .240 & .254 repectively. To allow routing to these hosts, you
> 
> can only set the subnet mask to 192.168.205.255, allowing access from the 
> whole 205
> network.
> 
> So I don't think you can achieve what you want.
> 
> Hope this helps anyway.
> 
> Cormac
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