Dell S4048T, Configuration Manual

Page: 91 / 1277

Denying and Permitting Access to a Terminal
Line
Dell Networking recommends applying only standard access control lists (ACLs) to deny and permit access to
VTY lines.
• Layer 3 ACLs deny all traffic that is not explicitly permitted, but in the case of VTY lines, an ACL with no
rules does not deny traffic.
• You cannot use the
show ip accounting access-list
command to display the contents of an ACL
that is applied only to a VTY line.
• When you use the
access-class access-list-name
command without specifying the
ipv4
or
ipv6
attribute, both IPv4 as well as IPv6 rules that are defined in that ACL are applied to the terminal.
This method is a generic way of configuring access restrictions.
• To be able to filter access exclusively using either IPv4 or IPv6 rules, use either the
ipv4
or
ipv6
attribute along with the
access-class access-list-name
command. Depending on the attribute
that you specify (
ipv4
or
ipv6
), the ACL processes either IPv4 or IPv6 rules, but not both. Using this
configuration, you can set up two different types of access classes with each class processing either
IPv4 or IPv6 rules separately.
To apply an IP ACL to a line, Use the following command.
• Apply an ACL to a VTY line.
LINE mode
access-class access-list-name [ipv4 | ipv6]
NOTE: If you already have configured generic IP ACL on a terminal line, then you cannot further apply
IPv4 or IPv6 specific filtering on top of this configuration. Similarly, if you have configured either IPv4 or
IPv6 specific filtering on a terminal line, you cannot apply generic IP ACL on top of this configuration.
Before applying any of these configurations, you must first undo the existing configuration using the
no
access-class access-list-name [ipv4 | ipv6]
command.
Example of an ACL that Permits Terminal Access
Example Configuration
To view the configuration, use the
show config
command in LINE mode.
Dell(config-std-nacl)#show config
!
ip access-list standard myvtyacl
seq 5 permit host 10.11.0.1
Dell(config-std-nacl)#line vty 0
Dell(config-line-vty)#show config
line vty 0
access-class myvtyacl
Dell(conf-ipv6-acl)#do show run acl
!
ip access-list extended testdeny
seq 10 deny ip 30.1.1.0/24 any
seq 15 permit ip any any
!
ip access-list extended testpermit
seq 15 permit ip any any
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