Users Guide

NOTE: You can only apply ACLs for Loopback to incoming trac.
To apply ACLs on Loopback, use the ip access-group command in INTERFACE mode. This example shows the interface
conguration status, adding rules to the access group, and displaying the list of rules in the ACL.
Example of Applying ACL Rules to a Loopback and Viewing ACL Conguration
Dell(conf)#interface loopback 0
Dell(conf-if-lo-0)#ip access-group abcd in
Dell(conf-if-lo-0)#show config
!
interface Loopback 0
no ip address
ip access-group abcd in
no shutdown
Dell(conf-if-lo-0)#end
Dell#configure terminal
Dell(conf)#ip access-list extended abcd
Dell(config-ext-nacl)#permit tcp any any
Dell(config-ext-nacl)#deny icmp any any
Dell(config-ext-nacl)#permit 1.1.1.2
Dell(config-ext-nacl)#end
Dell#show ip accounting access-list
!
Extended Ingress IP access list abcd on Loopback 0
seq 5 permit tcp any any
seq 10 deny icmp any any
seq 10 deny icmp any any
For more information, refer to the VTY Line Local Authentication and Authorization section in the Securitychapter.
IP Prex Lists
IP prex lists control routing policy.
An IP prex list is a series of sequential lters that contain a matching criterion (examine IP route prex) and an action (permit or
deny) to process routes. The lters are processed in sequence so that if a route prex does not match the criterion in the rst lter,
the second lter (if congured) is applied. When the route prex matches a lter, Dell Networking OS drops or forwards the packet
based on the lter’s designated action. If the route prex does not match any of the lters in the prex list, the route is dropped
(that is, implicit deny).
A route prex is an IP address pattern that matches on bits within the IP address. The format of a route prex is A.B.C.D/X where
A.B.C.D is a dotted-decimal address and /X is the number of bits that should be matched of the dotted decimal address. For
example, in 112.24.0.0/16, the rst 16 bits of the address 112.24.0.0 match all addresses between 112.24.0.0 to 112.24.255.255.
The following examples show permit or deny lters for specic routes using the le and ge parameters, where x.x.x.x/x represents a
route prex:
• To deny only /8 prexes, enter deny x.x.x.x/x ge 8 le 8.
• To permit routes with the mask greater than /8 but less than /12, enter permit x.x.x.x/x ge 8.
• To deny routes with a mask less than /24, enter deny x.x.x.x/x le 24.
• To permit routes with a mask greater than /20, enter permit x.x.x.x/x ge 20.
The following rules apply to prex lists:
• A prex list without any permit or deny lters allows all routes.
• An “implicit deny” is assumed (that is, the route is dropped) for all route prexes that do not match a permit or deny lter in a
congured prex list.
• After a route matches a lter, the lter’s action is applied. No additional lters are applied to the route.
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Access Control Lists (ACLs)