Static routes and subnetting

Yup, basically that it.

BTW, lets say you had:

10.0.0.0/26
10.0.0.64/26
10.0.0.192/26

Out one interface and

10.0.0.128/26

out another interface.

You could still use 10.0.0.0/24 on the first interface and 10.0.0.128/26 out the other interface, because more specific routes take preference over less specific routes.

What might, or might not be an issue, if there was no active 10.0.0.128/26, if you use 10.0.0.0/24 it will forward any traffic, with 10.0.0.128/26 as the destination, out that interface, which as the network 10.0.0.128/26 isn't there, would waste bandwidth sending traffic to it.

Hello
Just like to add that you may want also to add a null route for the summary on the rtr that holds the /24 this way any packets sent to hosts on any network within that summary towards that rtr that is not in use can be dropped gracefully without it being sent back out by a possible default route set on the same rtr thus avoiding routing loop..

example:
ip route 10.0.0.0 255.255.255.0 null0

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Paul

If all of the /26 networks are hosted on the same device, yes you can summarize with a single /24 route on your edge device.

For example, if all of the /26 networks are on a switch at 192.168.254.254 and you have a valid path from the router to the switch on that network, you could use a route on your edge router such as:

10.0.0.0 255.255.255.0 192.168.254.254

In this example, the switch would then figure out which /26 the traffic belongs to for further processing.

What you do with the traffic once it hits the switch would be irrelevant. You could even have 2 of the /26 networks on the switch directly connected to the edge router and then the other 2 /26 networks on a switch connected to the first switch, for example. The edge router would send the traffic to the switch it’s attached to and traffic for the 2 /26 network on the switch would stay there while traffic for the other 2 /26 networks would be sent to the other switch by a route statement you’d have on the 1st switch. jasonmoulding

There are many other possible scenarios you might have. Now, if you had 2 of the /26 networks on one switch and the other 2 /26 networks on another switch and BOTH of them were directly connected to the edge router, you would NOT be able to summarize the route as a /24 because traffic would then be sent to the wrong switch in some cases. So, you’d have to instead either use a route for each /26 or you could summarize into 2 /25 routes (1 pointing to each switch).

Hello
Yes you can however i would suggest if not all the that summary (/24) is being used at this time then append a static null route on the switch so it doesn't try to forward packets to non active subnets within that summary back towards the rtr or onwards via a default route

switch:
ip route 10.0.0.0 255.255.255.0 null 0.

Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul