Creating and applying an access list to interface can verify if traffic is making to or from a source/destination. In the following example I want to see if HTTP traffic is making to the subnet where my HTTP server is. First I create an access list.
access-list 100 deny tcp any any eq 0
access-list 100 deny udp any any eq 0
access-list 100 permit tcp host 192.x.y.z host 10.a.b.c eq 80 log
access-list 100 permit ip any any
Next apply the access list to the interface.
ip access-group 100 in
Now we send some traffic and then check the logs and the access list.
show log
%SEC-6-IPACCESSLOGP: list 100 permit tcp 192.x.y.z(30430) -> 10.a.b.c(80), 1 packet
show access-list 100
30 permit tcp any host 192.x.y.z host 10.a.b.c eq 80 log (4 matches)
