Ok, ton post est vieux... bientôt 10 ans... mais les réponses que tu as eu me désespères tellement, que je souhaite pporter la solution
Router#show access-list
Extended IP access list 125
10 permit icmp 10.x.x.x 0.0.0.255 any
20 permit icmp 20.x.x.x 0.0.0.255 any
30 permit icmp 30.x.x.x 0.0.0.255 any
Router#conf t
Router(config)#ip access-list extended 125
Router(config-ext-nacl)#no permit icmp 10.x.x.x 0.0.0.255 any
Router#sh access-lists
Extended IP access list 125
20 permit icmp 20.x.x.x 0.0.0.255 any
30 permit icmp 30.x.x.x 0.0.0.255 any
Router#sh voila