Interfaces
Use interface commands to configure globally scoped interface parameters. With these commands, you can override system defaults for sets of interfaces. Both physical and logical interfaces can be individually identified and their global parameters set. In addition, sets of physical interfaces can be specified by way of a "wildcarding" mechanism.
autonomous-system
Name
autonomous-system - specifies the autonomous system (AS) used to create an AS path associated with the interface route created from this interface
Syntax
autonomous-system as-number
no autonomous-system as-number?
Mode
Interface Configuration
Parameters
as-number - an integer between 1 and 65535, inclusive
Description
The autonomous-system command specifies the autonomous system that will be used to create an AS path associated with the route created from the definition of this interface. The autonomous system number of the router running Advanced Routing Suite is specified with the global AS command. The autonomous system numbers of BGP's peers is specified in BGP configuration. An interface defines a route known as an "interface route". Interface routes are also known as direct routes. Specifying an AS number on the interface will cause the direct route corresponding to the interface to be generated with a non-empty AS path. If this route is then exported into BGP, update messages advertising this route will include the specified AS in their AS path. Normally, the interface AS number is not set.
The negative of this command, no autonomous-system, removes the autonomous-system definition previously defined by the autonomous-system command and reverts to the default of no autonomous-system associated with this interface. Note: Specifying a value for as-number in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
By default, no AS number is associated with an interface.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example sets the AS for interface fxp1 to be 1439.
(config)# interface fxp1
(config-if)# autonomous-system 1439
disable
Name
disable - disables the associated interface
Syntax
disable
no disable
Mode
Interface Configuration
Parameters
none
Description
The disable command specifies that messages received on this interface must be ignored. The negative of this command, no disable, re-enables the interface.
Default
This option is not explicitly configured by default.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example disables inter face 192.168.15.1
(config)# interface 192.168.15.1
(config-if)# disable
preference
Name
preference - used to select the best route when multiple routes exist for the same destination
Syntax
preference pref
no preference pref?
Mode
Interface Configuration
Parameters
pref - an integer in the range of 0 to 255 inclusive, with 0 being the highest preference that a route may have. Note: Only direct routes (in other words, routes to subnets on directly connected interfaces) can have a preference of 0.
Description
Multiple routes can exist for the same destination prefix. In this situation, the route's preference is used to select the best route. For interface routes, preference sets the preference for routes to this interface when it is up.
The negative of this command, no preference, removes the configured preference and reverts to the default preference of 0. Note: Specifying a value for pref in the no form has no effect on the configuration. Thus, it is displayed above as optional.
Default
If preference is not configured, it is as if the user had configured the following:
(config-if)# preference 0
Command History
NGC 2.2 - This command was introduced.
Examples
The following example sets the preference for interface fxp1 to be 15.
(config)# interface fxp1
(config-if)# preference 15
primary-alias
Name
primary-alias - sets the primary logical address for a physical interface
Syntax
primary-alias [ ipv4-addr ipv4-address masklen len |
no primary-alias [ ipv4-addr ipv4-address masklen len |
Mode
Interface Configuration
Parameters
ipv4-addr ipv4-address masklen len - specifies an IPv4 address with a netmask. The value of len can be a number from 0 to 32, inclusive
Description
The primary-alias command is used to override the default selection of the primary logical interfaces on a given physical interface. There is exactly one primary interface for each subnet defined on a given physical interface. By default, Advanced Routing Suite selects the first logical read from the operating system for each subnet defined on the physical interface as a primary interface. The primary-alias command provides a way to specify which of the logical interfaces that share the same subnet is to be selected as primary for that subnet.
The negative of this command, no primary-alias removes the configured primary-alias command and reverts to the default primary addresses, which are the addresses of the first interfaces read from the kernel for each subnet on a physical interface. Note: Specifying parameters after no primary-alias has no effect on the configuration. Thus, they are displayed above as optional.
Default
The default primary addresses are the addresses of the first interfaces read from the kernel for each subnet on a physical interface.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures physical interface fxp1 and sets the primary-alias for that physical interface to 192.168.10.15 with a mask length of 24.
(config)# interface fxp1
(config-if)# primary-alias ipv4-addr 192.168.10.15 masklen 24
unnumbered
Name
unnumbered - configures the specified interface as an unnumbered interface
Syntax
unnumbered interface-name
no unnumbered interface-name
Mode
Interface Configuration
Parameters
interface-name - the name of the physical interface from which an interface address will be borrowed
Description
The unnumbered command indicates that the associated interface is an "unnumbered" interface. The purpose of unnumbered interfaces is to allow a network administrator to save IP address space. There are, by definition, only two machines on a serial or ppp link, and having to assign an IP subnet is an inefficient use of IP address space. In order to forward packets, a host or router must have an IP source address.
The IPv4 address of the first primary logical interface on the physical interface named by the interface-name parameter will be borrowed and used for the interface named in this command.
The term, "Unnumbered Interface" is actually a misnomer. The interfaces are not really unnumbered. What actually happens is the unnumbered interface borrows an IP address from another configured interface on the box to use as its source address.
With regards to unnumbered interfaces, the following assumptions are made:
- The p2p or serial link has a framing protocol for encapsulating IP packets (such as PPP or HDLC).
- The operating system provides a method for joining a multicast group on a physical interface by referring to the interface by name (such as "ppp1") or interface index.
- A supporting physical interface exists on the box that is configured with a valid IP address.
- A route can be installed in the OS forwarding table with a nexthop address of 0 or a nexthop specifying the physical interface.
The negative of this command, no unnumbered, removes the unnumbered definition previously configured with the unnumbered command and reverts to the default of the interface being a numbered interfaces.
Default
Interfaces are not unnumbered by default.
Command History
NGC 2.2 - This command was introduced.
Examples
The following example configures interface eth0 as an unnumbered interface.
(config)# interface eth0
(config-if)# unnumbered eth1
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