topic Access from one subnet to another in Network Security

Access from one subnet to another

Spinu Viorel — Wed, 13 Mar 2019 00:57:55 GMT

Hello,

I have a router. I connected 3 port so I have 3 subnets:

192.168.0.0/24 Fa0, 192.168.1.0/24 Fa1, and 192.168.2.0/24 Fa2

Now, I need to do:

Subnet 192.168.1.0 is the most secure so nobody should access it, except one host from 192.168.2.0 subnet(192.168.2.10), but users from 192.168.1.0 should access both 0.0 and 2.0 subnets.

Subnets 192.168.0.0 and 192.168.2.0 should access each otherwith no restriction.

I have configured this:

access-list 100 deny ip 192.168.0.0 0.0.0.255 192.168.1.0 0.0.0.255

access-list 100 deny ip 192.168.2.0 0.0.0.255 192.168.1.0 0.0.0.255

access-list 100 permit ip any any

int fast 1

access-group 100 out

but in this way if users from 192.168.1.0 try to access the other 2 subnet, the return trafic will match the access list 100 so subnet 192.168.1.0 is not able to access them.

Can u give me a solution please?

Thank U!

Re: Access from one subnet to another

acomiskey — Thu, 31 Jul 2008 14:16:01 GMT

I assume int fast 1 is 192.168.1.x?

access-list 100 permit tcp any 192.168.1.0 0.0.0.255 established

access-list 100 permit ip 192.168.2.10 0.0.0.0 192.168.1.0 0.0.0.255

int fast 1

access-group 100 out

Re: Access from one subnet to another

Spinu Viorel — Fri, 01 Aug 2008 11:53:58 GMT

yes, you assumed right and it is working

thanks a lot

Re: Access from one subnet to another

eplanchon — Fri, 01 Aug 2008 14:12:48 GMT

What kind of router do you have?

Re: Access from one subnet to another

Spinu Viorel — Fri, 01 Aug 2008 16:53:01 GMT

cisco 1812

Re: Access from one subnet to another

eplanchon — Fri, 01 Aug 2008 17:09:30 GMT

Thanks.

How do you define 3 subnets using this router?

Do you need to do VLAN?

Re: Access from one subnet to another

Spinu Viorel — Fri, 01 Aug 2008 17:19:12 GMT

yes...it is a little more complicated.

the subnets are connected via a switch HP with VLANS and I have access-list on every every subnet IN direction...but I was intrested in the problem with returning traffic (if u read my firs message)