If I have 2 routers that route back to the same gateway router and one of the routers is issuing a public /24 to customers, can the other router issue a smaller block within that same subnet without subnetting the first router?
We are running out of IP space and the router with the /24 is only using 100 of them, but since many customers have been givin static IP address I cannot re-subnet that network without calling a bunch of customers to change their mask and gateway.
Yes, you can. Routers always choose the most specific route - so if there’s a route for a /24 and a /25 that overlap, and the IP address is within the /25, the router will use the /25 route.
However, this is not good practice at all. For one, any router or device with an interface within the /24 will never be able to reach the /25 since they’ll think it is local when really it isn’t. The routers might get the /25 into their routing table and know, but clients generally speaking can’t do that.
Ok thanks for your reply. I’ts a temporary fix until I get IP space but this should get me by for a while. We are an ISP so don’t normally have a need for clients to talk to eathother anyway, but I’ll keep that in mind.
Thanks for the help!