connecting two different networks

[Altria]

Hello All,
This may be a silly question but how do I connect multiple networks that do
not have a common network IDs. Is this done thru the subnet mask? For
example, how would i share resources in networks such as;

A)111.222.0.0
B)222.0.0.0
C)333.1.20.0

I am sure that a router is involved but do I simply have to give them the
same subnet mask?
TIA
Altria

 

[Phillip Windell]

I can't tell you how to do it with fake numbers. The numbers you use
actually make a difference in how it is done. Yes, you must use a Router.
With three networks you need either two routers with two interfaces in each
or with one router that has three or more interfaces.

 

[Altria]

Hello Phillip,
Thanks for the quick response....
When you say interfaces, do u mean an interface (network interface?) for
each corresponding subnet. In the router do you add a route ip entry for all
the corresponding subnets and allow the arp table to be rebuilt?
Suppose there are routers already separating each of the different networks
is there a way that i can add each ip/subnet entry into it and allow the
router to forward packets to the appropriate destination?
How exactly would this be accomplished?
TIA,
Altria

I can't tell you how to do it with fake numbers. The numbers you use
actually make a difference in how it is done. Yes, you must use a Router.
With three networks you need either two routers with two interfaces in each
or with one router that has three or more interfaces.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

Hello All,
This may be a silly question but how do I connect multiple networks that do
not have a common network IDs. Is this done thru the subnet mask? For
example, how would i share resources in networks such as;

A)111.222.0.0
B)222.0.0.0
C)333.1.20.0

I am sure that a router is involved but do I simply have to give them the
same subnet mask?
TIA
Altria

 

[Phillip Windell]

When you say interfaces, do u mean an interface (network interface?) for
each corresponding subnet.
Yes.

In the router do you add a route ip entry for all the corresponding

subnets > and allow the arp table to be rebuilt?

When network is directly connected to a router the route table already know
about it. No manual entries are needed. No "routing protocols" are required
either. ARP is a Layer2 thing and is not even relevant to the discussion.

Suppose there are routers already separating each of the different networks
is there a way that i can add each ip/subnet entry into it and allow the
router to forward packets to the appropriate destination?
How exactly would this be accomplished?

Just because the routers exist doesn't mean you can. It depends on how the
system is built and wired up both physically and logically.

If eveything is built properly, then just enable RIP on each router and get
out of the way. It will take care of itself.

If everything comes into one single router, then it should already be
working unless someone has went out of their way to screw it up.

 

[Altria]

Thanks Philip,
So technically, It is just a matter of configuring the router and enabling
RIP so that all host IP addresses are obtained within the network.
Assuming a physical star topology and logical bus (Ethernet), the networks
reside in the same building.
TIA,
Altria

 

[Phillip Windell]

So technically, It is just a matter of configuring the router and enabling
RIP so that all host IP addresses are obtained within the network.

Not hosts addresses. Routers couldn't care less about host addresses. They
only concern themslves with the network portion of the IP#. But yes, config
the router properly, enable RIP, get out of the way.

Assuming a physical star topology and logical bus (Ethernet), the networks
reside in the same building.

It is the topology and where the routers are located in that topology that
matter. It doesn't matter where the buildings are. They could be in three
different countries and it wouldn't matter as long as the topology is
correct and supports the process.

 

[Dan]

Phillips Answer is one to do it - Using a Router between
the different nets.

But that requires hardware you may nothave or need. The
other approach in my mind is easier and cheaper.

First I'm assuming all three nets are present on the same
wire directly (not via a router route).

Go into the TCP/IP props in the advanced section add in a
static IP address for the other networks (all addresses
must be assigned you can't use DHCP in this config.) Once
you add each address you will also need to add the needed
masks.

OK, next step
Open up a DOS window then run 'ROUTE' This will give you
the Route tsble info. For help add '/?' with a space
between this will help you in setting up the Route service
which you may need to configure. As you know the default
Route (also called default gateway) sets which network and
upstream Router one needs to go to to get to the next
net. Assuming the primary IP address you have assigned to
the NIC network address space is the only pathway to gain
access to the next upstream network (via a Router or
firewall/Proxy system) you don't need to do anything
within the Route services as all of the other networks are
listed dynamically. If on the other hand one or more of
the other address networks you now have setup need to be
crossed to a router to still another network you will need
to either add the needed route entry every time you
restart your system or set a persistant entry.

Now using multiple networks on the same wire is not overly
smart. Ther are a few places it is needed but you appear
to be going to far here (DMZ). I would recommend not
having more than two nets on a given wire and have only
one network which needs to be routed across any router or
firewall. With server systems you may have multiple NICs
each used to isolate either given traffic types or
connection pathways. This is were I mostly use this trick
when two systems have muiltiple pathways between them and
I need to bias a given pathway and/or allow a given
process access to a different direction.

Sometimes the config is more complex were a static route
entry won't do. This is were adding a routing protocol
service onto the system might make better sense. Adding
RIP2 or OSPF or other routing protocol is the answer.
This allows the system to be a member of the routers route
updates yet not be a router (no interconnection between
the different NIC's or there nets).

 

[Phillip Windell]

Remember that the hosts on the network must have their Default Gateway set
to the router in their subnet.