Router on a stick

[u080570]

I have a relatively small network consisting of 3 sites - one connected via a Cisco 3600 router and the other connected via a VINA T1 Integrator to my main site. I am trying to figure out how to implement a new Class C IP network segment at my main site (the other 2 sites are already finished) over top of the current Class B segment (I have heard this is called 'router on a stick') so I dont have to change all addresses at once. I am currently using 199.0.0.x addresses (incorrectly subnetted with 255.255.0.0) and am changing to 10.1.30.x address scheme. I also have a CISCO PIX firewall if that is relevant.

Thanks for any assistance
Mark

 

[wybnormal]

One of the easiest ways to do something like this is to use secondary ip addressing. This allows the router interface to answer an IP address on the interface plus a second IP range.

!
interface fa0
ip address 128.124.1.1
ip address 131.108.1.1 secondary
!

Once you have the new IP subnet working correctly, you can remove the first ip address, the secondary becomes the primary and the downtime is as lone as it takes for the report to reset.

MikeS


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[Kaja1]

You say that you want to make a new ip segment which may suggest a physically separate ethernet segment. This would require a separate ethernet port on the router that would be configured with the new class c address.
You may have to take care with the routing protocol to prevent black holes.
If you are using Rip,IGRP or EIGRP, all the 10.x.x.o networks will all be seen as a single entry in the route table. This may be prevented using eigrp with the no summary command but Rip (ver 1) and igrp will only see the classful 10.0.0.0 network and not any subnets. Rip version 2 is able to see the subnets OSPF will see the subnets but will require extra config to enable the secondary address to be propergated if you use the secondary address method.

If you are simply trying to migrate addresses on an existing segment to the 10.1.30 address then the previous feedback is correct. Again be careful setting up the routing as the secondary address will not be automatically applied to the table.
The term "router on a stick" is normally used when a single physical connection is used to carry several vlans to the router so that traffic may be passed by routing between the vlans. That link would be configured as a vlan trunk.