interface p1

danielknowlab · ‎09-22-2016

Hi guys!! I've analyzing this case: I need to set the address on interface p2 of R1 to use as gateway for the /24 networks on SW2 - Can not plug SW2 directly to SW1 - Can not use VLANs - Using only Static Route (no protocol)

     [10.10.0.0/24] ---------------------------
                                              |
     [10.10.1.0/24 .. 10.10.3.0/24] ------------[SW1]--------
                                              |             |
     [10.10.4.0/24 .. 10.10.7.0/24] -----------             |                    
                                                            | p1: 10.10.0.0/21
                                                           [R1]------------------....
                                                            | p2: ???.???.???.???/??
                                                            |
                                                            |
     [10.10.8.0/24 .. 10.10.255.0/24] ----------[SW2]--------

Can use only static routes and I see direct and local connections to the interfaces at these networks I think no solution here, because 10.10.8.1/16 overlaps with R1:p1 interface address and can't set a mask to cover all subnets in the gateway. Any idea or solution?? how I must to configure p2 to set correctly the gateway to the sw2 networks? Thanks!!

rasmus.elmholt · ‎09-22-2016

And you can't use secondary addresses on the interfaces either?

If the clients have a /24 subnetmask they won't be able to contact R1 in your diagram because the GW adresses is outside their subnet.

danielknowlab · ‎09-23-2016

No, I don't know how I could do that. But yes the problem is the overlapping on p1 and p2, that are limiting the range covered on p2 mask. p1 is in /21 let communication with all networks on SW1 from 10.10.0.0/24 to 10.10.7.0/24. But p2 can't be /16 because overlaps with p1, then if for example set p2 as 10.10.8.1/24 or any other not at /16 then all SW2 networks range are not covered.

I think that gateway don't need to be connected directly to network range, I think that must be in route resolution. But in this case, the ranges are overlapping and the address on p2 are limited range, for example at /24 here route table:

10.0.0.0/8 is variably subnetted, 7 subnets, 5 masks

C 10.0.0.8/30 is directly connected, Serial0/0/0

L 10.0.0.9/32 is directly connected, Serial0/0/0

C 10.10.0.0/21 is directly connected, GigabitEthernet0/0

L 10.10.0.1/32 is directly connected, GigabitEthernet0/0

C 10.10.8.0/24 is directly connected, GigabitEthernet0/1

L 10.10.8.1/32 is directly connected, GigabitEthernet0/1

S 10.20.0.0/16 [1/0] via 10.0.0.10

I tried too assigning static route explicitly to the GigabitEthernet0/1 instead by the ip of the port to avoid the next hop router itself ip. Any way don't works and i don't believe that this is a good idea for workaround, but anyway it's my testting :)

10.0.0.0/8 is variably subnetted, 8 subnets, 5 masks

C 10.0.0.8/30 is directly connected, Serial0/0/0

L 10.0.0.9/32 is directly connected, Serial0/0/0

S 10.10.0.0/16 is directly connected, GigabitEthernet0/1

C 10.10.0.0/21 is directly connected, GigabitEthernet0/0

L 10.10.0.1/32 is directly connected, GigabitEthernet0/0

C 10.10.8.0/24 is directly connected, GigabitEthernet0/1

L 10.10.8.1/32 is directly connected, GigabitEthernet0/1

S 10.20.0.0/16 [1/0] via 10.0.0.10

At this point, I'm thinking that may be bridging the p2 to p1 may be the solution, not sure.

Any other solution or recommendation?

Thanks!

rasmus.elmholt · ‎09-23-2016

interface p1

ip address 10.10.0.1 255.255.255.0

ip address 10.10.1.1 255.255.255.0 secondary

ip address 10.10.2.1 255.255.255.0 secondary

etc.

danielknowlab · ‎09-23-2016

Ummm ... I solve this with only one address 10.10.0.0 255.255.248.0, for p1, but p2 can't be resumed on one address, then I take your idea and try add secondary ips grouping the SW2 networks ... I'm going to try!!

But, this is the habitual way to solve this?

rasmus.elmholt · ‎09-23-2016

This would be the way to make it work, but it is a workaround for a poor ip addressing scheme.

Normally you wouldn't split networks like this outside the bit boundaries..

danielknowlab · ‎09-23-2016

I'm analyzing as new addressing scheme, the idea is to set 10.A.B.node schema.

10: organization private network

A: brach (internal organization site / geographical network)

B: several subnet for each branch

But in some cases level/groups of subnetworks are need on same brach. This is the analyzing case in post. I don't want/waste to set another "A" range to this split on the branch.

In this case I'm analyzing the branch on 10.10.0.0/16 and splitting for one level 10.10.0.0/21 and other level for the rest range. /21 are not on bit boundary? what best practice for this kind of split?

danielknowlab · ‎09-23-2016

Not working for me, using a Cisco 1941:

ip address 10.10.9.0 255.255.255.0 secondary

^

% Invalid input detected at '^' marker.

But, this is the habitual way to solve this? we need to enter 247 secondary interfaces, this may impact on performance.

Gateway address for several subnets that can't be superneted in one entry