User Manual

401
Users Manual of XGS-6350-24X4C
say, you cannot add the command line to the designated access list. However, you can run no permit and no
deny to delete items from the access list.
When you create the access list, the end of the access list includes the implicit deny
sentence by default. If the mask is omitted in the relative IP host address access
list, 255.255.255.255 is supposed to be the mask.
After the access list is created, the access list must be applied on the route or
interface. For details, refer to section 4.2.3 “Applying the Access List to the
Interface”.
43.4.2.3 Applying the Access List to the Interface
After the access list is created, you can apply it to one or multiple interfaces including the in interfaces and
out interfaces.
Run the following command in interface configuration mode.
Run… To…
ip access-groupname {in | out}
Apply the access list to the interface.
The access list can be used on the in interfaces and the out interfaces. For the standard access list of the in
interface, the soured address of the packet is to be checked according to the access list after the packet is
received. For the extensible access list, the routing switch also checks the destination. If the access list
permits the address, the software goes on processing the packet. If the access list does not permit the
address, the software drops the packet and returns an ICMP unreachable message.
For the standard access list of the out interfaces, after a packet is received or routed to the control interface,
the software checks the source address of the packet according to the access list. For the extensible access
list, the routing switch also checks the access list of the receiving side. If the access list permits the address,
the software will send the packet. If the access list does not permit the address, the software drops the packet
and returns an ICMP unreachable message.
If the designated access list does not exist, all packets allows to pass.
43.4.2.4 Extensible Access List Example
In the following example, the first line allows any new TCP to connect the destination port after port 1023. The
second line allows any new TCP to connect the SMTP port of host 130.2.1.2.
ip access-list extended aaa
permit tcp any 130.2.0.0 255.255.0.0 gt 1023
permit tcp any 130.2.1.2 255.255.255.255 eq 25
interface vlan 10
ip access-group aaa in
Another example to apply the extensible access list is given. Suppose a network connects the Internet, you
expect any host in the Ethernet can create TCP connection with the host in the Internet. However, you expect
the host in the Internet cannot create TCP connection with the host in the Ethernet unless it connects the
SMTP port of the mail host.