07-06-2018 08:29 PM - edited 03-05-2019 10:44 AM
I set up very simple network. The first link was a point to point link with the address 10.0.0.0/30. I then had a link with 3 devices so used the subnet 10.0.0.8/29. Two routers could then ping the third and the third could ping them, but they couldn't ping each other. I'm sure the answer is very obvious to this question and I know its not best practice, but why didn't this set up work?
I changed the second segment to a 10.0.1.0/24 subnet and it worked fine.
07-06-2018 09:01 PM
Hello
what was the addressing you gave to these rtrs - was the subnet address correct on all three devices - i assume they were connected all via a switch
Also as they were all on the same subnet the rtrs didn’t require a default gateway or default route
res
paul
07-07-2018 11:44 AM
Hi Thank you for the response.
The routers in question are all in the same subnet. Both Routers 3 and 4 can ping router 2. Router 2 can ping 3 and 4.
However, router 3 and 4 cannot ping each other.
Ping from router 3 to 4:
Reply to request 0 from 10.0.0.9 received 12 ms
Reply to request 1 from 10.0.0.9 received 10 ms
Reply to request 2 from 10.0.0.9 received 12 ms
etc....
Ping from router 4 to 3:
....... timed out...
07-07-2018 01:06 AM
Hello,
provide a schematic drawing of what your topology looks like, including what is connected to what, and which IP addresses are used on which links.
07-07-2018 12:41 PM
Hi Thank you for the response. The routers in question are all in the same subnet. Both Routers 3 and 4 can ping router 2. Router 2 can ping 3 and 4. However, router 3 and 4 cannot ping each other. Ping from router 3 to 4: Reply to request 0 from 10.0.0.9 received 12 ms Reply to request 1 from 10.0.0.9 received 10 ms Reply to request 2 from 10.0.0.9 received 12 ms etc.... Ping from router 4 to 3: ....... timed out...
07-07-2018 01:21 PM
Hello,
check the routing tables: R1 only knows network 10.0.0.0/30, and R3 and R4 only know network 10.0.0.8/29. In order for all networks to be reachable, you need to run either a static default route on ech router, or a routing protocol.
So either:
R1
ip route 0.0.0.0 0.0.0.0 10.0.0.2
R3
ip route 0.0.0.0 0.0.0.0 10.0.0.9
R4
ip route 0.0.0.0 0.0.0.0 10.0.0.9
or on each router:
router rip
version 2
network 0.0.0.0
no auto-summary
07-07-2018 02:42 PM
A default route shouldn't be needed to communicate with a route on the same subnet though correct? The router 10.0.0.9 can ping 10.0.0.9 but not 10.0.0.11 even though they are both connected to the same switch.
07-07-2018 03:33 PM
07-08-2018 02:24 PM
Hello,
post the configurations of your routers...
07-08-2018 03:26 PM
It seems to me that Georg is trying to solve a different problem. He is concerned about Router 1 access to Router 3 and 4. While I agree that this is a valid concern, it is not what the original post is asking about. The question here is why Router 3 and Router 4 can not communicate. To answer this we need more information. We especially need to understand how Routers 2, 3, and 4 are connected. If this turns out to be a Frame Relay connection then it is likely that the issue is that Router 3 does not have a mapping of IP to DLCI for Router 4 (and similarly lacking a mapping on Router 4 for Router 3). If the connection is a switch, then we have a different issue. I agree with Georg that having the config of the routers will be very helpful.
HTH
Rick
07-09-2018 12:29 AM
I agree with Richard. For the sake of verification I recreated your setup in GNS3, and with Ethernet interfaces and IP addresses 10.0.0.9/28, 10.0.0.10/28, and 10.0.0.11/28 configured on the interfaces, every IP address can ping the respective other ones.
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