Consider the following example: I have two networks (192.168.1.0 and 192.168.2.0) with one PC in each network (PC0 - 192.168.1.1 and PC1 - 192.168.2.1) and a router R0 with 2 interfaces connecting these networks:
Then I configure a standard access list on the R0's Fa0/1 interface to block traffic outcoming from PC0 to PC1 as:
R0(config)#access-list 1 deny host 192.168.1.1
R0(config)#access-list 1 permit any
R0(config)#interface fa0/1
R0(config-if)#ip access-group 1 out
When I ping PC1 from PC0 I'm getting this result as expected:
C:\>ping 192.168.2.1
Pinging 192.168.2.1 with 32 bytes of data:
Reply from 192.168.1.10: Destination host unreachable.
Reply from 192.168.1.10: Destination host unreachable.
Reply from 192.168.1.10: Destination host unreachable.
Reply from 192.168.1.10: Destination host unreachable.
But when I try to ping PC0 from PC1, I'm getting
C:\>ping 192.168.1.1
Pinging 192.168.1.1 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Since the, "access-group 1 out" is configured in R0's interface Fa0/1, it should just only filter traffic coming from the outside, right? So my Ping request should be permitted, but I'm getting the unreachable response.
Why so? I would really appreciate a help on this one.