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Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and Services, Release 12.3 T
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Introduction
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IP Addressing and Services Commands: A through C
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IP Addressing and Services Commands: D through H
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IP Addressing and Services Commands: idle through ip local-proxy-arp
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IP Addressing and Services Commands: ip mask-reply through ip web-cache redirect
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IP Addressing and Services Commands: L through R
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IP Addressing and Services Commands: serverfarm through show ip nat
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IP Addressing and Services Commands: show ip nhrp through synguard
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IP Addressing and Services Commands: T through W
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Table Of Contents
term ip netmask-format
To specify the format in which netmasks are displayed in show command output, use the term ip netmask-format command in EXEC configuration mode. To restore the default display format, use the no form of this command.
term ip netmask-format {bitcount | decimal | hexadecimal}
no term ip netmask-format [bitcount | decimal | hexadecimal]
Syntax Description
bitcount
Number of bits in the netmask.
decimal
Netmask dotted decimal notation.
hexadecimal
Netmask hexadecimal format.
Defaults
Netmasks are displayed in dotted decimal format.
Command Modes
EXEC
Command History
Usage Guidelines
IP uses a 32-bit mask that indicates which address bits belong to the network and subnetwork fields, and which bits belong to the host field. This range of IP addresses is called a netmask. By default, show commands display an IP address and then its netmask in dotted decimal notation. For example, a subnet would be displayed as 131.108.11.55 255.255.255.0.
However, you can specify that the display of the network mask appear in hexadecimal format or bit count format instead. The hexadecimal format is commonly used on UNIX systems. The previous example would be displayed as 131.108.11.55 0XFFFFFF00.
The bitcount format for displaying network masks is to append a slash (/) and the total number of bits in the netmask to the address itself. The previous example would be displayed as 131.108.11.55/24.
Examples
The following example specifies that network masks for the session be displayed in bitcount notation in the output of show commands:
term ip netmask-format bitcountthreshold metric
To set a threshold metric other than the default value, use the threshold metric command in tracking configuration mode. To disable the threshold metric, use the no form of this command.
threshold metric {up number | down number}
no threshold metric {up number | down number}
Syntax Description
Defaults
No threshold is configured.
Command Modes
Tracking configuration
Command History
Usage Guidelines
This command is available only to IP-route threshold metric objects tracked by the track ip route metric threshold global configuration command.
The default up and down threshold values are 254 and 255, respectively. With these values, IP-route threshold tracking gives the same result as IP-route reachability tracking.
Examples
In the following example, the tracking process is tracking the IP-route threshold metric. The metric default value is changed to 16 for the up threshold and to 20 for the down threshold.
track 1 ip route 10.22.0.0/16 metric thresholdthreshold metric up 16 down 20delay down 20Related Commands
track ip route
Tracks the state of IP routing and enters tracking configuration mode.
threshold percentage
To set a threshold percentage for a tracked object in a list of objects, use the threshold percentage command in tracking configuration mode. To disable the threshold percentage, use the no form of this command.
threshold percentage {up number | down number}
no threshold percentage {up number | down number}
Syntax Description
up
Specifies the up threshold.
down
Specifies the down threshold.
number
Threshold value. Range is from 0 to 100.
Defaults
No threshold percentage is configured.
Command Modes
Tracking configuration
Command History
Usage Guidelines
When you configure a tracked list using the track object-number list command, there are two keywords available: boolean and threshold. If you specify the threshold keyword, you can specify either the percentage or weight keywords. If you specify the percentage keyword, then the weight keyword is unavailable. If you specify the weight keyword, then the percentage keyword is unavailable.
You should configure the "up" percentage first. The valid range is from 1 to 100. The down percentage depends on what you have configured for upe. For example, if you configure 50 percent for up, you will see a range from 0 to 49 percent for down.
Examples
In the following example, the tracked list 11 is configured to measure the threshold using an "up" percentage of 50 and a "down" percentage of 32.
track 11 list threshold percentageobject 1object 2threshold percentage up 50 down 32Related Commandse
threshold weight
Sets a threshold weight for a tracked object in a list of objects.
threshold weight
To set a threshold weight for a tracked object in a list of objects, use the threshold weight command in tracking configuration mode. To disable the threshold weight, use the no form of this command.
threshold weight {up number | down number}
no threshold weight {up number | down number}
Syntax Description
up
Specifies the up threshold.
down
Specifies the down threshold.
number
Threshold value. Range is from 1 to 255.
Defaults
No threshold weight is configured.
Command Modes
Tracking configuration
Command History
Usage Guidelines
When you configure a tracked list of objects using the track object-number list command, there are two keywords available: boolean and threshold. If you specify the threshold keyword, you can specify either the percentage or weight keywords. If you specify the weight keyword, then the percentage keyword is unavailable. If you specify the percentage keyword, then the weight keyword is unavailable.
You should configure the "up" weight first. The valid range is from 1 to 255. The available "down" weight depends on what you have configured for the "up" weight. For example, if you configure 25 for up, you will see a range from 0 to 24 for down.
Examples
In the following example, the tracked list 12 is configured to measure a threshold using a specified weight.
track 12 list threshold weightobject 1object 2threshold weight up 35 down 22Related Commands
threshold percentage
Sets a threshold percentage for a tracked object in a list of objects
track interface
To configure an interface to be tracked and to enter tracking configuration mode, use the track interface command in global configuration mode. To remove the tracking, use the no form of this command.
track object-number interface type number {line-protocol | ip routing}
no track object-number interface type number {line-protocol | ip routing}
Syntax Description
Defaults
No interface is tracked.
Command Modes
Global configuration
Command History
Usage Guidelines
This command reports a state value to clients. A tracked IP-routing object is considered up when the platform is routing IP, the interface line protocol is up, and IP routing is enabled and active on the interface.
Tracking the IP-routing state of an interface (using the track interface ip routing command) can be more useful in some situations than just tracking the line-protocol state (using the track interface line-protocol command).
Examples
In the following example, the tracking process is configured to track the IP-routing capability of serial interface 1/0:
track 1 interface serial1/0 ip routingRelated Commands
track ip route
To track the state of an IP route and to enter tracking configuration mode, use the track ip route command in global configuration mode. To remove the tracking, use the no form of this command.
track object-number ip route ip-address/prefix-length {reachability | metric threshold}
no track object-number ip route ip-address/prefix-length {reachability | metric threshold}
Syntax Description
Defaults
The route to the subnet address is not tracked.
Command Modes
Global configuration
Command History
Usage Guidelines
A tracked IP-route object is considered up and reachable when a routing-table entry exists for the route and the route is not inaccessible.
To provide a common interface to tracking clients, route metric values are normalized to the range of 0 to 255, where 0 is connected and 255 is inaccessible. The resulting value is compared against threshold values to determine the tracking state as follows:
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State is up if the scaled metric for that route is less than or equal to the up threshold.
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The tracking process uses a per-protocol configurable resolution value to convert the real metric to the scaled metric. The metric value communicated to clients is always such that a lower metric value is better than a higher metric value.
Use the threshold metric tracking configuration command to specify a threshold metric other than the default threshold metric.
Examples
In the following example, the tracking process is configured to track the reachability of 10.22.0.0/16:
track 1 ip route 10.22.0.0/16 reachabilityIn the following example, the tracking process is configured to track the threshold metric using the default threshold metric values:
track 1 ip route 10.22.0.0/16 metric thresholdRelated Commands
show track
Displays HSRP tracking information.
threshold metric
Sets a threshold metric other than the default value.
track list
To specify a list of objects to be tracked and the thresholds to be used for comparison, use the track list command in global configuration mode. To disable the tracked list, use the no form of this command.
track object-number list {boolean {and | or}} | {threshold {weight | percentage}}
no track object-number list {boolean {and | or}} | {threshold {weight | percentage}}
Syntax Description
Defaults
The list is not tracked.
Command Modes
Global configuration
Command History
Examples
A track list object may be configured to track two serial interfaces when both serial interfaces are "up" and when either serial interface is "down," for example:
track 1 interface serial2/0 line-protocoltrack 2 interface serial2/1 line-protocoltrack 100 list boolean andobject 1object 2A track list object may be configured to track two serial interfaces when either serial interface is "up" and when both serial interfaces are "down," for example:
track 1 interface serial2/0 line-protocoltrack 2 interface serial2/1 line-protocoltrack 101 list boolean orobject 1object 2A track list object may be configured to track two serial interfaces when both serial interfaces are "up" and when both serial interface is "down," for example:
track 1 interface serial2/0 line-protocoltrack 2 interface serial2/1 line-protocoltrack 102 threshold weightobject 1 weight 10object 2 weight 10threshold weight up 20 down 0The configuration shown above provides some hysteresis in case one of the serial interfaces is flapping.
Related Commands
track resolution
To specify resolution parameters for a tracked object, use the track resolution command in global configuration mode. To disable this functionality, use the no form of this command.
track resolution ip route {eigrp resolution-value | isis resolution-value | ospf resolution-value | static resolution-value}
no track resolution ip route {eigrp resolution-value | isis resolution-value | ospf resolution-value | static resolution-value}
Syntax Description
Defaults
The track ip route metric resolution default values are used.
Command Modes
Global configuration
Command History
Usage Guidelines
The track ip route command causes tracking of a route in the routing table. If a route exists in the table, the metric value is converted into a number in the range from 0 to 255. The metric resolution for the specified routing protocol is used to do the conversion. There are default values for the metric resolution but the track resolution command can be used to change the metric resolution default values.
Examples
In the following example, the EIGRP routing protocol has a resolution value of 280.
track resolution ip route eigrp 280Related Commands
track rtr
To track the state of a Service Assurance Agent (SAA) operation and to enter tracking configuration mode, use the track rtr command in global configuration mode. To remove the tracking, use the no form of this command.
track object-number rtr saa-id {state | reachability}
no track object-number rtr saa-id {state | reachability}
Syntax Description
Defaults
SAA tracking is disabled.
Command Modes
Global configuration
Command History
12.3(4)T
This command was introduced.
12.2(25)S
This command was integrated into Cisco IOS Release 12.2(25)S.
Usage Guidelines
Every SAA operation maintains an operation return-code value. This return code is interpreted by the tracking process. The return code may return OK, OverThreshold, and several other return codes. Different operations may have different return-code values, so only values common to all operation types are used.
Two aspects of an SAA operation can be tracked: state and reachability. The difference between these relates to the acceptance of the OverThreshold return code. Table 51 shows the state and reachability aspects of SAA operations that can be tracked.
Table 51 Comparison of State and Reachability Operations
State
OK
(everything else)
Up
Down
Reachability
OK or over threshold
(everything else)
Up
Down
In the following example, the tracking process is configured to track the state of SAA router 2.
track 1 rtr 2 stateIn the following example, the SAA tracking process is configured to track the reachability of SAA router 3.
track 2 rtr 3 reachabilitytrack timer
To specify the interval in which the tracking process polls the tracked object, use the track timer command in tracking configuration mode. To disable this functionality, use the no form of this command.
track timer {interface | ip route} seconds
no track timer {interface | ip route} seconds
Syntax Description
Defaults
If you do not use the track timer command to specify a polling interval, a tracked object will be tracked at the default polling interval.
Command Modes
Tracking configuration
Command History
Examples
In the following example, the tracking process is configured to poll the tracked interface every 3 seconds:
track timer interface 3transmit-interface
To assign a transmit interface to a receive-only interface, use the transmit-interface command in interface configuration mode. To return to normal duplex Ethernet interfaces, use the no form of this command.
transmit-interface type number
no transmit-interface
Syntax Description
type
Transmit interface type to be linked with the (current) receive-only interface.
number
Transmit interface number to be linked with the (current) receive-only interface.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
Receive-only interfaces are used commonly with microwave Ethernet links.
Examples
The following example specifies Ethernet interface 0 as a simplex Ethernet interface:
interface ethernet 1ip address 128.9.1.2transmit-interface ethernet 0update arp
To secure dynamic Address Resolution Protocol (ARP) entries in the ARP table to their corresponding DHCP bindings, use the update arp command in DHCP pool configuration mode. To disable this command and change secure ARP entries to dynamic ARP entries, use the no form of this command.
update arp
no update arp
Syntax Description
This command has no keywords or arguments.
Defaults
No default behavior or values.
Command Modes
DHCP pool configuration
Command History
Usage Guidelines
The update arp DHCP pool configuration command is used to secure ARP table entries and their corresponding DHCP leases. However, existing active leases are not secured. These leases will remain insecure until they are renewed. When the lease is renewed, it is treated as a new lease and will be secured automatically. If this feature is disabled on the DHCP server, all existing secured ARP table entries will automatically change to dynamic ARP entries.
This command can be configured only under the following conditions:
•
•
The configuration of this command is not visible to the client. When this command is configured, secured ARP table entries that are created by a DHCP server cannot be removed from the ARP table by the clear arp-cache command. This is designed behavior. If a secure ARP entry created by the DHCP server must be removed, the clear ip dhcp binding command can be used. This command will clear the DHCP binding and secured ARP table entry.
Note
Examples
The following example configures the Cisco IOS DHCP server to secure ARP table entries to their corresponding DHCP leases within the DHCP pool named WIRELESS-POOL:
Router(config)# ip dhcp pool WIRELESS-POOLRouter(dhcp-config)# update arpRouter(dhcp-config)# exitRelated Commands
update dns
To dynamically update the Domain Name System (DNS) with address (A) and pointer (PTR) Resource Records (RRs) for some address pools, use the update dns command in global configuration mode. To disable dynamic updates, use the no form of this command.
update dns [both | never] [override] [before]
no update dns [both | never] [override] [before]
Syntax Description
Defaults
No updates are performed.
Command Modes
Global configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Usage Guidelines
If you configure the update dns both override command, the DHCP server will perform DDNS updates for both PTR and A RRs associated with addresses assigned from an address pool, even if the DHCP client specified in the FQDN that the server should not.
If the server is configured using this command with or without any of the other keywords, and if the server does not see an FQDN option in the DHCP interaction, then it will assume that the client does not understand DDNS and act as though it were configured to update both A and PTR records on behalf of the client.
Examples
The following example shows how to configure the DHCP to never update the A and PTR RRs:
update dns neverRelated Commands
utilization mark high
To configure the high utilization mark of the current address pool size, use the utilization mark high command in DHCP pool configuration mode. To remove the high utilization mark, use the no form of this command.
utilization mark high percentage-number
no utilization mark high percentage-number
Syntax Description
Defaults
The default high utilization mark is 100 percent of the current pool size.
Command Modes
DHCP pool configuration
Command History
Usage Guidelines
The current pool size is the sum of all addresses in all the subnets in the pool. If the utilization level exceeds the configured high utilization mark, the pool will schedule a subnet request.
This command cannot be used unless the autogrow size option of the origin command is configured.
Examples
The following example sets the high utilization mark to 80 percent of the current pool size:
utilization mark high 80Related Commands
origin
Configures an address pool as an on-demand address pool.
utilization mark low
Configures the low utilization mark of the current address pool size.
utilization mark low
To configure the low utilization mark of the current address pool size, use the utilization mark low command in DHCP pool configuration mode. To remove the low utilization mark, use the no form of this command.
utilization mark low percentage-number
no utilization mark low percentage-number
Syntax Description
Defaults
The default low utilization mark is 0 percent of the current pool size.
Command Modes
DHCP pool configuration
Command History
Usage Guidelines
The current pool size is the sum of all addresses in all the subnets in the pool. If the utilization level drops below the configured low utilization mark, a subnet release is scheduled from the address pool.
This command cannot be used unless the autogrow size option of the origin command is configured.
Examples
The following example sets the low utilization mark to 20 percent of the current pool size:
utilization mark low 20Related Commands
origin
Configures an address pool as an on-demand address pool.
utilization mark high
Configures the high utilization mark of the current address pool size.
virtual
To configure virtual server attributes, use the virtual virtual server configuration command. To remove the attributes, use the no form of this command.
virtual ip-address {tcp | udp} port-number [service service-name]
no virtual
Syntax Description
Defaults
No default behavior or values.
Command Modes
SLB virtual server configuration
Command History
12.0(7)XE
This command was introduced.
12.1(5)T
This command was integrated into Cisco IOS Release 12.1(5)T.
Usage Guidelines
The no virtual command is allowed only if the virtual server was removed from service by the no inservice command.
For some applications, it is not feasible to configure all the virtual server TCP or UDP port numbers for the IOS SLB feature. To support such applications, you can configure IOS SLB virtual servers to accept flows destined for all ports. To configure an all-port virtual server, specify a port number of 0.
Note
Examples
The following example specifies that the virtual server with the IP address 10.0.0.1 performs load balancing for TCP connections for the port named www. The virtual server processes HTTP requests.
ip slb vserver PUBLIC_HTTPvirtual 10.0.0.1 tcp wwwRelated Commands
ip slb vserver
Identifies a virtual server.
show ip slb vservers
Displays information about the virtual servers.
vrf
To associate the on-demand address pool with a VPN routing and forwarding instance (VRF) name, use the vrf command in DHCP pool configuration mode. To remove the VRF name, use the no form of this command.
vrf name
no vrf name
Syntax Description
Defaults
No default behavior or values
Command Modes
DHCP pool configuration
Command History
Usage Guidelines
Associating a pool with a VRF allows overlapping addresses with other pools that are not on the same VRF. Only one pool can be associated with each VRF. If the pool is configured with the origin dhcp command or origin aaa command, the VRF information is sent in the subnet request. If the VRF is configured with an RFC 2685 VPN ID, the VPN ID will be sent instead of the VRF name.
Examples
The following example associates the on-demand address pool with a VRF named red:
ip dhcp pool red_poolorigin dhcp subnet size initial 24 autogrow 24utilization mark high 85utilization mark low 15vrf redRelated Commands
vrrp authentication
To authenticate Virtual Router Redundancy Protocol (VRRP) packets received from other routers in the group, use the vrrp authentication command in interface configuration mode. To disable VRRP authentication, use the no form of this command.
vrrp group authentication {text-string | text text-string | md5 {key-string [0 | 7 | key-string] | key-chain key-chain}
no vrrp group authentication {text-string | text text-string | md5 {key-string [0 | 7 | key-string] | key-chain key-chain}
Syntax Description
