sh ip route shows 10.0.0.0/8 is variably subnetted

[mahesh18]

Hi all,

Router A

sh run int loopback 1

Building configuration...

Current configuration : 63 bytes

!

interface Loopback1

ip address 10.10.0.1 255.255.255.0

sh ip int brief

Loopback1                  10.10.0.1       YES NVRAM  up                    up

Loopback2                  10.10.1.1       YES NVRAM  up                    up

Loopback3                  10.10.2.1       YES NVRAM  up                    up

Loopback4                  10.10.3.1       YES NVRAM  up                    up

Router B  i did sh ip route and it shows

     10.0.0.0/8 is variably subnetted, 10 subnets, 3 masks???????????????????????????????

D EX    10.10.0.0/24 [170/26137600] via 10.1.24.2, 11:18:01, Serial0/0?????????????????????

D EX    10.10.1.0/24 [170/26137600] via 10.1.24.2, 11:18:02, Serial0/0

D EX    10.10.2.0/24 [170/26137600] via 10.1.24.2, 11:18:02, Serial0/0

D EX    10.10.3.0/24 [170/26137600] via 10.1.24.2, 11:18:02, Serial0/0

Can someone please explain me why 10.0.0.0/8 shows in router Bs   routing table.

seems it is using default subnet mask of class A.

Is it default behaviour to show default subnet mask of classless routing protocol?

But it shows also more specfic routes loopback address  from router A  like 10.10.3.0/24 .

We are using classless routing protocol which is EIGRP.

Thanks

mahesh

[Kevin Dorrell]

I presume these routes are crossing a link that is not in network 10.0.0.0/8.  Put the command no auto-summary in the eigrp section of your configs, and I think the summary route will disappear.

Kevin Dorrell

Luxembourg

[mahesh18]

Hi Kevin,

Thanks for reply.

EIGRP section has already no auto summary configured.

MAhesh

[Reza Sharifi]

Hi Mahesh,

Can someone please explain me why 10.0.0.0/8 shows in router Bs

You probably have redistribute connected on router A's EIGRP that is why the show up in router B routing table

HTH

[Richard Burts · Accepted solution]

Kevin

It has been a long time since I have seen posts from you - welcome back

What Mahesh has shown is not a summary route.

10.0.0.0/8 is variably subnetted, 10 subnets, 3 masks

is not a summary route (it has not next hop information for one thing) and is only the introductory statement that says that class A network 10.0.0.0 is present in the routing table - and that there are 10 subnets of that network present in the routing table and that collectively those subnets have 3 different subnet masks.

Reza

Since the routes in the routing table show as D EX  they are certainly redistributed and it is certainly likely that this was redistribute connected.

Mahesh

To answer your question - yes it is normal behavior that when using a classless routing protocol (and implementing classless routing in the router) that there will be an introductory line stating the classful network (10.0.0.0) with its default mask (/8) when there are multiple subnets of that network in the routing table and some of the subnets use different subnet masks.

HTH

Rick

[mahesh18]

Hi Rick,

Many thanks for your reply.

Its always good to read your replies.

Need to learn lot more from this forum .

Best regards

MAhesh