Why can't I ping to a router on a different port?

[AWCyber]

I'm configuring OSPF authentication in a lab on Packet Tracer. I have two PCs, two Catalyst 2960 switches, and three 4331 routers. I have configured PC-A and R1 and I tried pinging them, but I noticed something while I was pinging them.

Here is my setup so far:

• A cable connects Fa0 on PC-A to Fa0/6 on Switch0
• A cable connects from Fa0/5 on Switch0 to G0/0/0 on R1.
• A cable connects from G0/0/1 on R1 to G0/0/0 on R2.
• I have configured PC-A with 192.168.1.3 (IP), 255.255.255.0, and 192.168.1.1 (Default Gateway)
• On R1, I have configured G0/0/0 with 10.1.1.1 and 255.255.255.252, and G0/0/1 with 192.168.1.1 and 255.255.255.0. It has no domain lookup, and the OSPF authentication is network 192.168.1.0 0.0.0.255 area 0 and network 10.1.1.0 0.0.0.3 area 0.

When I try to ping both port IP addresses on R1 from PC-A, I don't get a response and it times out. However, when I switch the cables and connect from Fa0/5 to G0/0/1 on R1 and G0/0/0 on R1 to G0/0/0 on R2, the ping works. Why does it work when I put the cables in different ports?

[Martin L]

attach your PT file but it must be in a zip format

Regards, ML
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[AWCyber]

Oh okay, my apologies.

[Martin L]

PT odes not show Port IDs; u can change that in PT options; 

for a router to communicate to directly connected router (or any device) and exchange routes with L3 device (via same protocol like ospf) that link must be on the same network, aka subnet; I.e. R1 to R2 is on  10.1.1.x/30; R2 to R3 is on 10.1.2.x/30 while Router LAN to PCs is on 192.168.1.x /24 subnet

Often we can make simple mistake by connecting cables in wrong ports. 

Regards, ML
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[AWCyber]

Thank you for the explanation. I apologize if this sounds dumb, but I'm still not quite understanding. I have switched the cables to their proper ports, and I now have PC-A on 192.168.1.3/24 (Fa0), R1 on 10.1.1.1/30 (G0/0/0) and 192.168.1.1/24 (G0/0/1) and I am able to ping both R1 ports from PC-A now.

How is PC-A able to ping G0/0/0 on R1 if the two devices are on two different networks?

[Martin L]

no, it should not be able to reach each others; notice that in file u shared PC A is on left connecting Router 0 not R1, some links are down; missing IPs.

In order for PCA to reach R1 ((on right) and PC-C via R0 and R2, all routers must exchange routes; have IPs and interfaces in UP UP state.  

i will attach my solution later ...

Regards, ML
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[Martin L]

here is your file as example with RIP; you can add OSPF; or reload routers w/o saving to remove RIP configs then add OSPF

Regards, ML
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