-
Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3 T
-
IP Routing Protocol Commands: T Through V
-
Introduction
-
IP Routing Protocol Commands: A
-
IP Routing Protocol Commands: B
-
IP Routing Protocols Commands: C through H
-
IP Routing Protocols Commands: ignore lsa mospf through ip ospf transmit-delay
-
IP Routing Protocol Commands: ip policy route-map through is-type
-
IP Routing Protocols Commands: K through M
-
IP Routing Protocols Commands: N
-
IP Routing Protocols Commands: O through R
-
IP Routing Protocols Commands: send-lifetime through set-overload-bit
-
IP Routing Protocols Commands: show bgp nsap through show ip bgp update-group
-
IP Routing Protocols Commands: show ip cache policy through show ip local policy
-
IP Routing Protocol Commands: show ip ospf through synchronization
-
Table Of Contents
ip prefix-list sequence-number
ip rip authentication key-chain
isis retransmit-throttle-interval
ip policy route-map
To identify a route map to use for policy routing on an interface, use the ip policy route-map command in interface configuration mode. To disable policy routing on the interface, use the no form of this command.
ip policy route-map map-tag
no ip policy route-map map-tag
Syntax Description
map-tag
Name of the route map to use for policy routing. The name must match a map-tag value specified by a route-map command.
Defaults
No policy routing occurs on the interface.
Command Modes
Interface configuration
Command History
Usage Guidelines
You might enable policy routing if you want your packets to take a route other than the obvious shortest path.
The ip policy route-map command identifies a route map to use for policy routing. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which policy routing is allowed for the interface, based on the destination IP address of the packet. The set commands specify the set actions—the particular policy routing actions to perform if the criteria enforced by the match commands are met. The no ip policy route-map command deletes the pointer to the route map.
Policy routing can be performed on any match criteria that can be defined in an extended IP access list when using the match ip address command and referencing an extended IP access list.
Examples
The following example sends packets with the destination IP address of 172.120.16.18 to a router at IP address 172.130.3.20:
interface serial 0ip policy route-map wethersfield!route-map wethersfieldmatch ip address 172.120.16.18set ip next-hop 172.130.3.20Related Commands
ip policy-list
To create a Border Gateway Protocol (BGP) policy list, use the ip policy-list command in policy-map configuration mode. To remove a policy list, use the no form of this command.
ip policy-list policy-list-name {permit | deny}
no ip policy-list policy-list-name
Syntax Description
policy-list-name
Name of the configured policy list.
permit
Permits access for matching conditions.
deny
Denies access to matching conditions.
Defaults
This command is not enabled by default.
Command Modes
Policy-map configuration mode
Command History
12.0(22)S
This command was introduced.
12.2(15)T
This command was integrated into 12.2(15)T.
Usage Guidelines
When a policy list is referenced within a route map, all the match statements within the policy list are evaluated and processed. Two or more policy lists can be configured with a route map. Policy- lists configured within a route map are evaluated with AND semantics or OR semantics. A policy list can also coexist with any other preexisting match and set statements that are configured within the same route map but outside of the policy list. When multiple policy lists perform matching within a route map entry, all policy lists match on the incoming attribute only.
Examples
In the following example, a policy list is configured that permits matches on the autonomous system path and metric:
Router(config)# ip policy-list POLICY-LIST-NAME-1 permitRouter(config-policy-list)# match as-path 1Router(config-policy-list)# match metric 10Router(config-policy-list)# endIn the following example, a policy list is configured that permits traffic that matches the specified community:
Router(config)# ip policy-list POLICY-LIST-NAME-2 permitRouter(config-policy-list)# match community 20Router(config-policy-list)# match metric 10Router(config-policy-list)# ip community-list 20 permit 20:1Router(config-policy-list)# endIn the following example, a policy list is configured that denies traffic that matches the specified community:
Router(config)# ip policy-list POLICY-LIST-NAME-3 denyRouter(config-policy-list)# match community 20Router(config-policy-list)# match metric 10Router(config-policy-list)# endRelated Commands
ip prefix-list description
To add a text description of a prefix list, use the ip prefix-list description command in global configuration mode. To remove the text description, use the no form of this command.
ip prefix-list list-name sequence-number description text
no ip prefix-list list-name sequence-number description text
Syntax Description
list-name
Specifies the prefix-list name.
sequence-number
Specifies the prefix-list entry.
text
Adds a text description. Up to 80 characters can be entered.
Defaults
No default behavior or values
Command Modes
Global configuration
Command History
Usage Guidelines
The ip prefix-list description command is used to add a text description to an IP prefix list. The prefix list description can be up to 80 characters in length.
Examples
In the following example, a prefix list description added to the prefix list named RED that states that routes are permitted from network A:
Router(config)# ip prefix-list RED description Permit routes from network ARelated Commands
ip prefix-list sequence-number
To enable the generation of default sequence numbers for entries in a prefix list, use the ip prefix-list sequence-number command in global configuration mode. To suppress default generation of sequence numbers, use the no form of this command.
ip prefix-list sequence-number
no ip prefix-list sequence-number
Syntax Description
This command has no arguments or keywords.
Defaults
Default sequence numbers are generated when an IP prefix list is configured.
Command Modes
Global configuration
Command History
Examples
The following example suppresses the automatic generation of default sequence numbers for prefix list entries:
Router(config)# no ip prefix-list sequence-numberRelated Commands
ip prefix-list
To create a prefix list or add a prefix-list entry, use the ip prefix-list command in global configuration mode. To delete a prefix-list entry, use the no form of this command.
ip prefix-list list-name | list-number [seq number] {deny network/length | permit network/length} [ge length] [le length]
no ip prefix-list list-name | list-number [seq number] {deny network/length | permit network/length} [ge length] [le length]
Syntax Description
Defaults
An implicit deny is applied to traffic that does match any prefix-list entry.
A prefix list is processed as an exact match when the le or ge keyword is not entered.
If a sequence number is entered when configuring this command, a default sequence numbering is applied to the prefix list. The number 5 is applied to the first prefix entry, and subsequent unnumbered entries are incremented by 5.
Command Modes
Global configuration
Command History
Usage Guidelines
The ip prefix-list command is used to configure IP prefix filtering. Prefix lists are configured with permit or deny keywords to either permit or deny the prefix based on the matching condition. A prefix list consists of an IP address and a bit mask. The IP address can be a classful network, a subnet, or a single host route. The bit mask is entered as a number from 1 to 32.
Prefix lists are configured to match an exact prefix length or a prefix range. The ge and le keywords are used to specify a range of the prefix lengths to match, providing more flexible configuration than can be configured with just the network/length argument. The prefix list is processed using an exact match when neither ge nor le keyword is entered. If only the ge value is entered, the range is the value entered for the ge length argument to a full 32-bit length. If only the le value is entered, the range is from value entered for the network/length argument to the le length argument. If both the ge length and le length keywords and arguments are entered, the range falls between the values used for length arguments. The following formula shows this behavior:
network/length < ge length < le length <= 32
A prefix list is configured with a name and/or sequence number. One or the other must be entered when configuring this command. If a sequence number is not entered, a default sequence number of 5 is applied to the prefix list, and subsequent prefix list entries will be increment by 5 (for example, 5, 10, 15, and etc). If a sequence number is entered for the first prefix list entry but not subsequent entries, then the subsequent entries will also be incremented by 5 (For example, if the first configured sequence number is 3, then subsequent entries will be 8, 13,18, and etc). Default sequence numbers can be suppressed by entering the no form of this command with the seq keyword.
Prefix lists are evaluated starting with the lowest sequence number. The longest most specific prefix is matched. The first successful match is processed for a given prefix. Once a match occurs, the permit or deny statement is processed, and the rest of the list is not evaluated.
Tips
For best performance, the most frequently processed prefix list statements should be configured with the lowest sequence numbers. The seq number keyword and argument can be used for resequencing.
The prefix list is applied to inbound or outbound updates for specific peer by entering the neighbor prefix-list command. Prefix list information and counters are displayed in the output of the show ip prefix-list command. Prefix-list counters can be reset by entering the clear ip prefix-list command.
Examples
In the following example, a prefix list configured to deny the default route 0.0.0.0/0:
Router(config)# ip prefix-list RED deny 0.0.0.0/0In the following example, a prefix list is configured to permit traffic from the 172.16.1.0/24 subnet:
Router(config)# ip prefix-list BLUE permit 172.16.1.0/24In the following example, a prefix list is configured to permit routes from the 10.0.0.0/8 network that have a mask length that is less than or equal to 24 bits:
Router(config)# ip prefix-list YELLOW permit 10.0.0.0/8 le 24In the following example, a prefix list is configured to deny routes from the 10.0.0.0/8 network that have a mask length that is greater than or equal to 25 bits:
Router(config)# ip prefix-list PINK deny 10.0.0.0/8 ge 25In the following example, a prefix list is configured to routes to permit routes from any network that have a mask length from 8 to 24 bits:
Router(config)# ip prefix-list GREEN permit 0.0.0.0/0 ge 8 le 24In the following example, a prefix list configured to deny any route with any mask length from the 10.0.0.0/8 network:
Router(config)# ip prefix-list ORANGE deny 10.0.0.0/8 le 32Related Commands
ip rip authentication key-chain
To enable authentication for Routing Information Protocol (RIP) Version 2 packets and to specify the set of keys that can be used on an interface, use the ip rip authentication key-chain command in interface configuration mode. To prevent authentication, use the no form of this command.
ip rip authentication key-chain name-of-chain
no ip rip authentication key-chain [name-of-chain]
Syntax Description
Defaults
No authentication is provided for RIP packets.
Command Modes
Interface configuration
Command History
Usage Guidelines
If no key chain is configured with the key-chain command, no authentication is performed on the interface (not even the default authentication).
Examples
The following example configures the interface to accept and send any key belonging to the key chain named trees:
ip rip authentication key-chain treesRelated Commands
ip rip authentication mode
To specify the type of authentication used in Routing Information Protocol (RIP) Version 2 packets, use the ip rip authentication mode command in interface configuration mode. To restore clear text authentication, use the no form of this command.
ip rip authentication mode {text | md5}
no ip rip authentication mode
Syntax Description
Defaults
Clear text authentication is provided for RIP packets.
Command Modes
Interface configuration
Command History
Usage Guidelines
RIP Version 1 does not support authentication.
Examples
The following example configures the interface to use MD5 authentication:
ip rip authentication mode md5Related Commands
ip rip receive version
To specify a Routing Information Protocol (RIP) version to receive on an interface basis, use the ip rip receive version command in interface configuration mode. To follow the global version rules, use the no form of this command.
ip rip receive version [1] [2]
no ip rip receive version
Syntax Description
1
(Optional) Accepts only RIP Version 1 packets on the interface.
2
(Optional) Accepts only RIP Version 2 packets on the interface.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to override the default behavior of RIP as specified by the version command. This command applies only to the interface being configured. You can configure the interface to accept both RIP versions.
Examples
The following example configures the interface to receive both RIP Version 1 and Version 2 packets:
ip rip receive version 1 2The following example configures the interface to receive only RIP Version 1 packets:
ip rip receive version 1Related Commands
ip rip send version
To specify a Routing Information Protocol (RIP) version to send on an interface basis, use the ip rip send version command in interface configuration mode. To follow the global version rules, use the no form of this command.
ip rip send version [1] [2]
no ip rip send version
Syntax Description
1
(Optional) Sends only RIP Version 1 packets out the interface.
2
(Optional) Sends only RIP Version 2 packets out the interface.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command to override the default behavior of RIP as specified by the version command. This command applies only to the interface being configured.
Examples
The following example configures the interface to send both RIP Version 1 and Version 2 packets out the interface:
ip rip send version 1 2The following example configures the interface to send only RIP Version 2 packets out the interface:
ip rip send version 2Related Commands
ip rip receive version
Specifies a RIP version to receive on an interface basis.
version
Specifies a RIP version used globally by the router.
ip rip triggered
To enable triggered extensions to Routing Information Protocol (RIP), use the ip rip triggered command in interface configuration mode. To disable triggered extensions to RIP, use the no form of this command.
ip rip triggered
no ip rip triggered
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
When triggered extensions to RIP are enabled, routing updates are sent on the WAN only if one of the following events occurs:
•
•
•
•
You might want to enable this feature if you are using an on-demand circuit and you are charged for usage time. Fewer routing updates will incur lower usage costs.
Entries in the routing database can be either temporary or semipermanent. Entries learned from broadcasts on LANs are temporary; they will expire if not periodically refreshed by more broadcasts.
Entries learned from a triggered response on the WAN are semipermanent; they do not time out like other entries. Certain events can cause these routes to time out, such as the interface going down, or if the outgoing interface is the same as the incoming interface. Neighbor updates of the routes with a metric of 16 (infinity) mean the route is unreachable, and those routes are eventually removed from the routing table.
Examples
The following example enables triggered extensions to RIP:
interface serial 0ip rip triggeredRelated Commands
show ip rip database
Displays the contents of the RIP private database when triggered extensions to RIP are enabled.
ip rip v2-broadcast
To allow Routing Information Protocol (RIP) Version 2 update packets to be sent as broadcast packets instead of multicast packets, use the rip v2-broadcast command in interface configuration mode. To disable the broadcast of IP RIP Version 2 update packets that are sent as broadcast packets, use the no form of this command.
ip rip v2-broadcast
no ip rip v2-broadcast
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default. Unless the ip rip v2-broadcast commend is entered, RIP Version 2 update packets are sent as multicast packets.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use the ip rip v2-broadcast command to broadcast RIP Version 2 broadcast updates to hosts that do not listen to multicast broadcasts. Version 2 updates (requests and responses) will be sent to the IP broadcast address 255.255.255.255 instead of the IP multicast address 244.0.0.9.
In order to reduce unnecessary load on those hosts that are not listening to RIP Version 2 broadcasts, the system uses an IP multicast address for periodic broadcasts. The IP multicast address is 244.0.0.9.
Note
Examples
The following example configures Version 2 IP broadcast updates on RIP Ethernet interface 3/1:
Router(config) interface ethernet3/1Router(config-if) ip address 172.1.1.1 255.255.255.0Router(config-if) ip rip v2-broadcast...Router(config-if) router ripRouter(config-if) version 2Router(config-if) network 172.0.0.0Enter debug ip rip command to verify that RIP Version 2 IP broadcast updates are being sent to the IP broadcast address 255.255.255 instead of IP multicast address 244.0.0.9:
Router# debug ip rip14:41:59: RIP: sending v2 update to 255.255.255.255 via Ethernet3/1 (172.1.1.1)If the ip rip v2-broadcast command has not been entered, the output from the debug ip rip command verifies that the RIP Version 2 IP broadcast updates are being sent to the IP multicast address 244.0.0.9:
Router# debug ip rip15:45:16: RIP: sending v2 update to 244.0.0.9 via Ethernet3.1 (172.1.1.1)Related Commands
ip route
To establish static routes, use the ip route command in global configuration mode. To remove static routes, use the no form of this command.
ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent | track number] [tag tag]
no ip route prefix mask
Syntax Description
Defaults
No static routes are established.
Command Modes
Global configuration
Command History
Usage Guidelines
The establishment of a static route is appropriate when the Cisco IOS software cannot dynamically build a route to the destination.
If you specify an administrative distance, you are flagging a static route that can be overridden by dynamic information. For example, routes derived with Interior Gateway Routing Protocol (IGRP) have a default administrative distance of 100. To have a static route that would be overridden by an IGRP dynamic route, specify an administrative distance greater than 100. Static routes have a default administrative distance of 1.
Static routes that point to an interface on a connected router will be advertised by way of Routing Information Protocol (RIP), IGRP, and Enhanced Interior Gateway Routing Protocol (EIGRP) regardless of whether redistribute static commands are specified for those routing protocols. This situation occurs because static routes that point to an interface are considered in the routing table to be connected and hence lose their static nature. Also, the target of the static route should be included in the network (DHCP) command. If this condition is not met, no dynamic routing protocol will advertise the route unless a redistribute static command is specified for these protocols. With the following configuration:
rtr1 (serial 172.16.188.1/30)--------------> rtr2(Fast Ethernet 172.31.1.1/30) ------>router [rip | eigrp | igrp]network 172.16.188.0network 172.31.0.0•
ip route 172.16.188.252 255.255.255.252 FastEthernet0/0RIP and IGRP do not redistribute the route with the following ip route command because of the split horizon algorithm:
ip route 172.16.188.252 255.255.255.252 serial2/1•
ip route 172.16.188.252 255.255.255.252 FastEthernet0/0ip route 172.16.188.252 255.255.255.252 serial2/1With the Open Shortest Path First (OSPF) protocol, static routes that point to an interface are not advertised unless a redistribute static command is specified.
Adding a static route to an Ethernet or other broadcast interface (for example, ip route 0.0.0.0 0.0.0.0 Ethernet 1/2) will cause the route to be inserted into the routing table only when the interface is up. This configuration is not generally recommended. When the next hop of a static route points to an interface, the router considers each of the hosts within the range of the route to be directly connected through that interface, and therefore it will send Address Resolution Protocol (ARP) requests to any destination addresses that route through the static route.
The practical implication of configuring the ip route 0.0.0.0 0.0.0.0 Ethernet 1/2 command is that the router will consider all of the destinations that the router does not know how to reach through some other route as directly connected to Ethernet interface 1/2. So the router will send an ARP request for each host for which it receives packets on this network segment. This configuration can cause high processor utilization and a large ARP cache (along with memory allocation failures). Configuring a default route or other static route that directs the router to forward packets for a large range of destinations to a connected broadcast network segment can cause your router to reload.
Specifying a numerical next hop that is on a directly connected interface will prevent the router from using proxy ARP. However, if the interface with the next hop goes down and the numerical next hop can be reached through a recursive route, you may specify both the next hop and interface (for example, ip route 0.0.0.0 0.0.0.0 Ethernet 1/2 10.1.2.3) with a static route to prevent routes from passing through an unintended interface.
The track number keyword and argument combination specifies that the static route will be installed only if the state of the configured track object is up.
Examples
The following example chooses an administrative distance of 110. In this case, packets for network 10.0.0.0 will be routed to a router at 172.31.3.4 if dynamic information with an administrative distance less than 110 is not available.
ip route 10.0.0.0 255.0.0.0 172.31.3.4 110
Note
The following example routes packets for network 172.31.0.0 to a router at 172.31.6.6:
ip route 172.31.0.0 255.255.0.0 172.31.6.6The following example routes packets for network 192.168.1.0 directly to the next hop at 10.1.2.3. If the interface goes down, this route is removed from the routing table and will not be restored unless the interface comes back up.
ip route 192.168.1.0 255.255.0.0 Ethernet 0 10.1.2.3The following example installs the static route only if the state of track object 123 is up:
ip route 0.0.0.0 0.0.0.0 Ethernet 0/1 10.1.1.242 track 123Related Commands
ip route priority high
To assign a high priority to an Integrated Intermediate System-to-Intermediate System (IS-IS) IP prefix, use the ip route priority high command in router configuration mode. To remove the IP prefix priority, use the no form of this command.
ip route priority high tag tag-value
no ip route priority high tag tag-value
Syntax Description
tag tag-value
Assigns a high priority to IS-IS IP prefixes with a specific route tag in a range from 1 to 4294967295.
Defaults
No IP prefix priority is set.
Command Modes
Router configuration
Command History
Usage Guidelines
When you use the ip route priority high command to tag higher priority IS-IS IP prefixes for faster processing and installation in the global routing table, you can achieve faster convergence. For example, you can help Voice over IP (VoIP) gateway addresses get processed first to help VoIP traffic get updated faster than other types of packets.
Examples
The following example uses the ip route priority high command to assign a tag value of 100 to the IS-IS IP prefix:
Router> enableRouter# configure terminalRouter(config)# interface Ethernet 0Router(config-if)# ip router isisRouter(config-if)# isis tag 100!Router(config)# router isisRouter(config)# ip route priority high tag 100!Related Commands
ip route profile
To enable IP routing table statistics collection, use the ip route profile command in global configuration mode. To disable collection of routing table statistics, use the no form of the command.
ip route profile
no ip route profile
Syntax Description
This command has no arguments or keywords.
Defaults
The time interval for each sample, or sampling interval, is a fixed value and is set at 5 seconds.
Command Modes
Global configuration
Command History
Usage Guidelines
The ip route profile command helps you to monitor routing table fluctuations that can occur as the result of route flapping, network failure, or network restoration.
This command identifies route flapping over brief time intervals. The time interval for each sample, or sampling interval, is a fixed value and is set at 5 seconds.
Two sets of statistics are collected. The per-interval statistics are collected over a sampling interval, while the routing table change statistics are the result of aggregating the per-interval statistics. The per-interval statistics are collected as a single set of counters, with one counter tracking one event. All counters are initialized at the beginning of each sampling interval; counters are incremented as corresponding events occur anywhere in the routing table.
At the end of a sampling interval, the per-interval statistics for that sampling interval are integrated with the routing table change statistics collected from the previous sampling intervals. The counters holding the per-interval statistics are reset and the process is repeated.
Routing table statistics are collected for the following events:
•
•
•
•
•
Use the show ip route profile command to display the routing table change statistics.
Examples
The following example enables the collection of routing table statistics:
ip route profileRelated Commands
ip route static adjust-time
To change the time interval for IP static route adjustments during convergence, use the ip route static adjust-time command in global configuration mode. To reinstate the default adjustment time of 60 seconds, use the no form of this command.
ip route static adjust-time seconds
no ip route static adjust-time seconds
Syntax Description
Defaults
seconds: 60
Command Modes
Global configuration
Command History
Usage Guidelines
By default, static route adjustments are made every 60 seconds. To adjust the timer to any interval from 1 to 60 seconds, enter the ip route static adjust-time command.
The benefit of reducing the timer from the 60-second default value is to increase the convergence when static routes are used. However, reducing the interval can be CPU intensive if the value is set very low and a large number of static routes are configured.
Examples
In the following example, the adjustment time for static routes has been changed from the default 60 seconds to 30 seconds:
Router(config)# ip route static adjust-time 30To remove the 30-second adjusted time interval and reinstate the default 60-second value, enter the no route ip static adjust-time command:
Router(config)# no ip route static adjust-time 30Related Commands
ip router isis
To configure an IS-IS routing process for IP on an interface and to attach an area designator to the routing process, use the ip router isis command in interface configuration mode. To disable IS-IS for IP, use the no form of the command.
ip router isis area-tag
no ip router isis area-tag
Syntax Description
