ACL Specific Prefix Question

[Iloveyou]

In the ACL list 

10 permit icmp 10.0.0.0/8 host y.y.y.y

The above line does not work UNLESS I use a more specific subnet which in this case is 10.1.1.0/24.

So I have to put the line below.  

10 permit icmp 10.1.1.0/24 host y.y.y.y

Can someone explain to me why the more general subnet mask will not work?

Isnt the 10.0.0.0/8 subnet supposed to include all the 10 subnet?

[MHM Cisco World]

You are totally correct' the 10.0.0.0/8 must work BUT it can other issue effect this traffic.

One of them is NATing 

Other is Routing 

Can you share the config and topolgy let me check it

MHM

[Iloveyou]

10.1.1.1/24 is configured on my laptop.

This is no other network since I just configured the subnet on my laptop for testing purposes only.

[MHM Cisco World]

1-NAT issue
debug ip nat 
2-routing issue
in ACL add in end 
deny any any log 

this will give you hint if it not routing issue, if traffic pass through other interface

MHM

[balaji.bandi]

Can you explain more what is not work ? that permit statement - what is y.y.y.y (is part of that  that supernet ?)

what devices is this /X  should use wild mask for the ACL to accept ?

[Iloveyou]

y.y.y.y is the specific ip address of the destination host.

As of now I am using a laptop for testing.

what is /X should sue subnet mask?

[balaji.bandi]

You need to post more configuration here and give us the device mode and IOS code running

how these connected ?

10 permit icmp 10.0.0.0/8 host y.y.y.y   - this not work from your Laptop are you not able to ping this y.y.y.y ? where is y.y.y.y connected. ? how is your topology looks like ?

[Iloveyou]

This is the configuration, it is a C1111 router

line vty 0 4
access-class TESTACL in
privilege level 15
login local
transport input ssh

ip access-list extended TESTACL
10 permit ip 10.0.0.0 0.0.0.255 host 10.0.0.3

interface Vlan3
ip address 10.0.0.3 255.255.255.0

interface GigabitEthernet0/1/3
switchport access vlan 3
switchport mode access

The topology is that I connect my laptop to Gi0/1/3 with ip address 10.0.0.2/24 configured.

The ACL : 10 permit ip 10.0.0.0 0.0.0.255 host 10.0.0.3 works.

But 10 permit ip 10.0.0.0 0.255.255.255 host 10.0.0.3 doesnt work. 

Any specific reason?

I dont know. maybe i got my subnet mask wrong.