Re: Multihoming

apf3885 · ‎02-19-2002

Currently I have a class C network that is attached to the internet. I would like to keep my current setup, but extend the class C over a private network to another location. In the end there would be two class C's sharing the same internet connection but seperated by a private network. I would like to do this without subnetmasking. Other than it being very sloppy and ugly is it at all possible?

svermill · ‎02-19-2002

No. You would need to subnet your class c address space accordingly. Traffic gets delivered to a (sub)network as a whole, so it needs to all be in one place. But simple subnetting and static routes are not a big challenge to set up.

Kevin Dorrell · ‎02-20-2002

If the machines on each site are going to be pretty well fixed, then your best bet to to subnet, and configure each machine for the site where it will be used.

If, on the other hand the new site is a small remote office, and you want to move machines from one site to the other without reconfiguring, you could try using ip local-area mobility. Each machine is natively on one site or the other. There is a routing protocol running between the two sites. And the ip addresses of the mobile machines are declared as mobile. Each time a machine appears on its "non-native" site, the routers use the routing protocol to create a host route for that machine on its home network. A bit like the "roaming" feature on your GSM cellphone.

See http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/np1_c/1cprt2/1cipadr.htm#3652

kasey.hohenbrink · ‎02-22-2002

Ok - this begs the question...is the second class c address network on the internet? if not, then you only have a simple route issue. if it is, then you would need to have a higher routing protocol with an AS number.

I would like to know the telco involved. if you have a T1 to SiteA and a ISP T1 to SiteA, a T1 between SiteA and SiteB. then you can route siteB default to SiteA via the private network. unfortunately the ISP won't route any of the second class c networks address space back to you. you will need to NAT and that obviates the need for the second class C.