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Re: [suse-security] Advice Please - Extending a Network


thanks for the advice.  I am pursuing both upgrade paths we have discussed,
but find the one presented by you a challenge.

I have added an ISA Coax Ethernet Card into the machine (eth2) (I only had
an ISA slot left).  My current internal net is on eth0 and my Cable Modem
sits on eth1.  Hopefully I have followed all your advice below and also
added in SuSEfirewall2 FW_ALLOW_CLASS_ROUTING="yes" to permit the two local
nets to talk without having explicit forwarding instructions.  They are
192.168.0.xxx (original) and 192.168.1.xxx (new).

However, when I swap the coax cable over to eth2 I cannot get it to assign
any IP addresses to hosts.. Do I have to wait for the Lease Time to expire ?

Also as soon as I bring up the eth2 interface, with all my hosts on eth0,
they can still communicate to one another BUT I lose access to the internet
from all hosts.  Does the sequence the interface come up when booting matter
?  As it stands I they come up as eth0 - first local net; eth1 -
cable/internet; eth2 - new local net.

Any ideas ?

----- Original Message -----
From: "Carl Peto" <carl@xxxxxxxxxxxxxxxxxxxxx>
To: "Philip B Cook" <philipbcook@xxxxxxxxxxxx>; <suse-security@xxxxxxxx>
Sent: Monday, January 12, 2004 5:39 PM
Subject: Re: [suse-security] Advice Please - Extending a Network

> Philip,
> If you want to run two seperate subnets then you'll need to update various
> bits of config.  I'm going to be a bit pathetic and not describe it very
> fully as I've got a cold (!) and a major server crash to handle today!
> Sorry if this isn't as good as it could be.
> I am assuming that you are running a DHCP server that serves IP addresses
> and updates DNS for one simple subnet at present.
> Before you start, when the new card is in you'll use YaST2 to configure
> new card with an appropriate IP address.  If you decide to use the
> 192.168.10. subnet for the new NIC then might be a good
> suggestion for the new NIC IP address.
> Firstly DHCP.  Decide on a new subnet.  Probably something on a different
> class, like 192.168.10.xxx would be a good idea, just for simplicity.  Add
> another entry to dhcp.conf for this new subnet.  Given that you worked out
> how to do the first DHCP subnet in dhcp.conf I reckon you can work out how
> to add another?
> Second DNS.  Add new zone data for the new subnet.  You'll probably be
> some made up domain at the moment with a zone file for this.  You should
> also have a reverse lookup zone file for the existing 192.168.0 subnet.
> Copy this to create a new reverse lookup zone file for the new (e.g.
> 192.168.10.) subnet.  Modify named.conf accordingly too, make sure that
> new zone definition allows update from localhost (or whatever address
> configured) so that DHCP can update it dynamically.
> Those two bits should be easy ish for you.
> SuSEfirewall2, you just add the new Ethernet NIC device (probably eth2?)
> the FW_DEV_INT line where the existing internal NIC (probably eth1?) is.
> Also make sure to add the new subnet to FW_MASQ_NETS.
> I'm not sure about squid.  If any changes are needed to support two
> instead of one then they should be fairly obvious.
> Finally and the most nasty of all is Samba and WINS.  If you have only win
> 2k/XP clients then you are probably fairly home free.  You should be able
> ping clients on one subnet from the other and vice versa and should then
> able to see file shares/printers using the usual \\pc2\sharename "UNC"
> notation in the Windows Explorer Address Bar box, luckily for you you can
> thereby bypass the horrid NetBIOS and WINS mess.  I'm not sure how Network
> Neighbourhood works in that case (it probably just doesn't) but that's
> really just a user training issue in the end (arguably) and not worth the
> hassle.
> However if you've got Win 3.1, Win 98, Win ME, Win NT 4.0 or likewise
> clients on *any* of your connected PCs they won't be able to network
> the dreaded NetBIOS over TCP/IP ("NBT"), worse luck. :(
> In that case the best thing to do is get DHCP to set all of them up as
> "hybrid" nodes (use "man dhcp.conf" for info), with a NBNS ("WINS") server
> at ... (your Linux box IP address on *that* subnet being configured).
> adjust smb.conf (my preferred method is using SWAT over a webbrowser if
> running) so that "wins support = yes".  Next make sure all PCs are in the
> same WORKGROUP, restart Samba, DNS, DHCP, SuSEfirewall2 and all MS clients
> and pray.
> If you network the two segments together at an ethernet level you'll save
> all that hassle, however!  Mind you, arguably, you'll learn less in the
> (possibly slightly painful) process... :)
> Regards,
> Carl Peto
> Linux Server Support
> Bookman Associates
> ----- Original Message -----
> From: "Philip B Cook" <philipbcook@xxxxxxxxxxxx>
> To: <suse-security@xxxxxxxx>
> Sent: Sunday, January 11, 2004 8:03 AM
> Subject: Fw: [suse-security] Advice Please - Extending a Network
> >
> > > If the hardware solutions described are not an option then you have
> > > options using Linux (i) seperate subnets or (ii) a bridge.  The latter
> > > consists of extra modules in the kernel which effectively turn your
> > into
> > > a switch, thus saving the expense, and all LAN traffic goes across
> > > segments.  Alternatively split the LAN into two subnets, have two IP
> > > addresses, one for each NIC and have DHCP serve different IP addresses
> to
> > > hosts on each segment.  This is more traditional in some ways but can
> > > annoying for users, depending on what applications they use.  For
> instance
> > > if they are SMB clients that want to browse a "Network Neighbourhood"
> then
> > > you'll need to implement a WINS server (and possibly a domain server)
> > > keep the two subnets talking to each other.
> > >
> > > Carl Peto
> > > Linux Server Support
> > > Bookman Associates
> >
> > It seems to be quite hard to find an 8 port hub with a coax connector,
> > though I will keep looking.
> >
> > In the meantime can you expand on what I need to do following your (i)
> > seperate subnets suggestion.
> >
> > I am already running  ...
> >
> > 1) DHCP(providing IP addresses to the local machines and also updating
> > DNS zone files automatically)
> > 2) DNS (administering the local domain and forwarding to my Cable
> Company's
> > DNS servers)
> > 3) SuSEFirewall2 (blocks everything inbound, there are NO services
> > accessible from the internet other than those initiated by the local
> network
> > machines)
> > 4) Samba to support Windows Clients
> > 5) Squid
> >
> > so I think I have all the parts running I need, but need some pointers
> > how to add the extra interface into the settings for each.
> >
> > Thanks everyone for your advice.
> >
> > Philip
> >
> >
> > --
> > Check the headers for your unsubscription address
> > For additional commands, e-mail: suse-security-help@xxxxxxxx
> > Security-related bug reports go to security@xxxxxxx, not here
> >

Check the headers for your unsubscription address
For additional commands, e-mail: suse-security-help@xxxxxxxx
Security-related bug reports go to security@xxxxxxx, not here