Subnetting Question

skywolaskywola Posts: 9Member ■□□□□□□□□□
Here is the diagram:

What I am trying to accomplish, is create a route to the network in the colored square from Router2.
On router 2, which I have telneted into, I am entering the following:

R2(config)#ip route
%Inconsistent address and mask

The routing table in R3 is as follows: is variably subnetted, 2 subnets, 2 masks
C is directly connected, FastEthernet0/1
C is directly connected, FastEthernet0/0
S* [1/0] via

I have entered :
R2(config)#ip classless
in both R2 and R3, so that cannot be the issue.
I am using 2811 routers, I'm not sure it that could be a factor or not.
Cisco IOS Software, 2800 Software (C2800NM-IPBASE-M), Version 12.3( 8 ) T5, RELEASE
Given that Router1 and Router2 are ok with the addresses subnetted using, it seems that
Router3 should be ok with . . . . . . I tried just to see what would happen
and got the same message. My quess is that it has something to do with the way R2 is subnetted . . . . but
why that would be an issue escapes me. It's likely either the router itself or a newby issue . . . icon_rolleyes.gif

I went back to R3, and found that the address on Fa0/1 was not listed correctly, so I did this:
R3(config-if)#int f0/1
R3(config-if)#ip address
R3(config-if)#no sh
R3(config-if)#int f0/0
R3(config-if)#ip address
% overlaps with FastEthernet0/1

The network on Fa0/1 is, available addresses and with broadcast address
The network for f0/0 should be, so I should be able to use with the mask I
would think!


  • skywolaskywola Posts: 9Member ■□□□□□□□□□
    I'm answering part of my own question . . . .

    R2(config)#ip route

    The problem appears to be that, when entering the ip route statement, it should be the network, not the actual
    address . . . . ip route;
    The easiest solution is to change the ip address for f0/0 to, then in the routing table in R2 use
    ip route
    although, to me, it seems like you would be able to do it the way I tried to do it.
    using . . . . but anyway, using
  • volfkhatvolfkhat Posts: 944Member ■■■■■■■□□□
    Im at work... so don't have the time to better study your pic.

    BUT what strikes me as ODD:

    Router 3's Internal Nic:

    But your Host is:

    So... not sure what address you are trying to go for...
    although assuming ?
  • aldoilici1aldoilici1 Junior Member Posts: 9Member ■■□□□□□□□□
    you listed R3 routing table as:

    C is directly connected, FastEthernet0/0

    It's a different network from what you have on diagram
    CCNA R&S, CCNA Cyber Ops, GSEC, GMON
  • DeathmageDeathmage Posts: 2,496Banned
    C is your problem. in the network ID and your broadcast ID is, so your workable range is to

    Remember a /30 only has 2 workable addresses, one side for one router the other side for the remote connecting router.

    With that being said your 1st address is which would be in the 2nd subnet of a /30, while your next hop is in the 1st subnet which is illegal.

    Also since it's a /30 your mask would be not that would be a /26 or subnets of 64.

    Might be a good idea to go on Google and search 'Subnetting Workbook', it will be the 1st result and print it out and work through them.

    It's just a mix up with subnetting bit it's very important to master.


    Keep at it!
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