Table Of Contents

EIGRP Prefix Limit Support

Finding Feature Information

Contents

Prerequisites for EIGRP Prefix Limit Support

Restrictions for EIGRP Prefix Limit Support

Information About EIGRP Prefix Limit Support

Misconfigured VPN Peers

EIGRP Prefix Limit Support Overview

Protecting the Router from External Peers

Limiting the Number of Redistributed Prefixes

Protecting the Router at the EIGRP Process Level

Warning-Only Mode

Restart, Reset, and Dampening Timers and Counters

Restart Timer

Restart Counter

Reset Timer

Dampening Mechanism

How to Configure the Maximum-Prefix Limit

Configuring the Maximum Number of Prefix Accepted from Peering Sessions: Autonomous System Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Configuring the Maximum Number of Prefixes Accepted from Peering Sessions: Named Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Configuring the Maximum Number of Prefixes Learned Through Redistribution: Autonomous System Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Configuring the Maximum Number of Prefixes Learned Through Redistribution: Named Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Configuring the Maximum-Prefix Limit for an EIGRP Process: Autonomous System Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Configuring the Maximum-Prefix Limit for an EIGRP Process: Named Configuration

Inherited Timer Values

Prerequisites

Restrictions

Troubleshooting Tips

Examples

Configuration Examples for Configuring the Maximum-Prefix Limit

Example: Configuring the Maximum-Prefix Limit for a Single Peer—Autonomous System Configuration

Example: Configuring the Maximum-Prefix Limit for a Single Peer—Named Configuration

Example: Configuring the Maximum-Prefix Limit for All Peers—Autonomous System Configuration

Example: Configuring the Maximum-Prefix Limit for All Peers—Named Configuration

Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Autonomous System Configuration

Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Named Configuration

Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Autonomous System Configuration

Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Named Configuration

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for EIGRP Prefix Limit Support

EIGRP Prefix Limit Support

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First Published: August 9, 2004

Last Updated: November 20, 2009

The EIGRP Prefix Limit Support feature introduces the capability to limit the number of prefixes per VRF that are accepted from a specific peer or to limit all prefixes that are accepted by an Enhanced Interior Gateway Routing Protocol (EIGRP) process through peering and redistribution. This feature is designed to protect the local router from external misconfiguration that can negatively impact local system resources; for example, a peer that is misconfigured to redistribute full Border Gateway Protocol (BGP) routing tables into EIGRP. This feature is enabled under the IPv4 VRF address family and can be configured to support the MPLS VPN Support for EIGRP Between Provider Edge and Customer Edge feature.

For more information about EIGRP MPLS VPN configuration, refer to the "EIGRP MPLS VPN PE-CE Site of Origin" module.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for EIGRP Prefix Limit Support" section.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for EIGRP Prefix Limit Support

•Restrictions for EIGRP Prefix Limit Support

•Information About EIGRP Prefix Limit Support

•How to Configure the Maximum-Prefix Limit

•Configuration Examples for Configuring the Maximum-Prefix Limit

•Additional References

•Feature Information for EIGRP Prefix Limit Support

Prerequisites for EIGRP Prefix Limit Support

•Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) services have been configured between the Provider Edge (PE) routers and the customer edge (CE) routers at the customer sites.

Restrictions for EIGRP Prefix Limit Support

•This feature is supported only under the IPv4 VRF address family and can be used only to limit the number of prefixes that are accepted through a VRF.

•The EIGRP Prefix Limiting Support feature is enabled only under the IPv4 VRF address-family. A peer that is configured to send too many prefixes or a peer that rapidly advertises and then withdraws prefixes can cause instability in the network. This feature can be configured to automatically reestablish a disabled peering session at the default or user-defined time interval or when the maximum-prefix limit is not exceeded. However, the configuration of this feature alone cannot change or correct a peer that is sending an excessive number of prefixes. If the maximum-prefix limit is exceeded, you will need to reconfigure the maximum-prefix limit or reduce the number of prefixes that are sent from the peer.

Information About EIGRP Prefix Limit Support

•Misconfigured VPN Peers

•EIGRP Prefix Limit Support Overview

•Warning-Only Mode

•Restart, Reset, and Dampening Timers and Counters

Misconfigured VPN Peers

In MPLS VPNs, the number of routes that are permitted in the VPN routing and forwarding instance (VRF) is configured with the maximum routes VRF configuration command. However, limiting the number routes permitted in the VPN does not protect the local router from a misconfigured peer that sends an excessive number of routes or prefixes. This type of external misconfiguration can have a negative effect on the local router by consuming all available system resources (CPU and memory) in processing prefix updates. This type of misconfiguration can occur on a peer that is not within the control of the local administrator.

EIGRP Prefix Limit Support Overview

The EIGRP Prefix Limit Support feature provides the ability to configure a limit on the number of prefixes that are accepted from EIGRP peers or learned through redistribution. This feature can be configured on per-peer or per-process basis and can be configured for all peers and processes. This feature is designed to protect the local router from misconfigured external peers by limiting the amount of system resources that can be consumed to process prefix updates.

Protecting the Router from External Peers

This feature can be configured to protect an individual peering session or protect all peering sessions. When this feature is enabled and the maximum-prefix limit has been exceeded, the router will tear down the peering session, clear all routes that were learned from the peer, and then place the peer in a penalty state for the default or user-defined time period. After the penalty time period expires, normal peering will be reestablished.

Limiting the Number of Redistributed Prefixes

This feature can be configured to limit the number of prefixes that are accepted into the EIGRP topology table through redistribution from the Routing Information Base (RIB). All sources of redistribution are processed cumulatively. When the maximum-prefix limit is exceeded, all routes learned through redistribution are discarded and redistribution is suspended for the default or user-defined time period. After the penalty time period expires, normal redistribution will occur.

Protecting the Router at the EIGRP Process Level

This feature can be configured to protect the router at the EIGRP process level. When this feature is configured at the EIGRP process level, the maximum-prefix limit is applied to all peering sessions and to route redistribution. When the maximum-prefix limit is exceeded, all sessions with the remote peers are torn down, all routes learned from remote peers are removed from the topology and routing tables, all routes learned through redistribution are discarded, and redistribution and peering are suspended for the default or user-defined time period.

Warning-Only Mode

The EIGRP Prefix Limit Support feature has two modes of operation. This feature can control peering and redistribution per default and user-defined values or this feature can operate in warning-only mode. In warning-only mode the router will monitor the number of prefixes learned through peering and/or redistribution but will not take any action when the maximum-prefix limit is exceeded. Warning-only mode is activated only when the warning-only keyword is configured for any of the maximum-prefix limit commands. Only syslog messages are generated when this mode of operation is enabled. Syslog messages can be sent to a syslog server or printed in the console. These messages can be buffered or rate limited per standard Cisco IOS system logging configuration options. For more information about system logging in Cisco IOS software, refer to the "Troubleshooting and Fault Management" module.

Restart, Reset, and Dampening Timers and Counters

The EIGRP Prefix Limit Support feature provides two user-configurable timers, a restart counter, and a dampening mechanism. When the maximum-prefix limit is exceeded, peering and/or redistribution is suspended for a default or user-defined time period. If the maximum-prefix limit is exceeded too often, redistribution and/or peering will be suspended until manual intervention is taken.

Restart Timer

The restart timer determines how long the router will wait to form an adjacency or accept redistributed routes from the RIB after the maximum-prefix limit has been exceeded. The default restart-time period is 5 minutes.

Restart Counter

The restart counter determines the number of times a peering session can be automatically reestablished after the peering session has been torn down or after the a redistributed routes have been cleared and relearned because the maximum-prefix limit has been exceeded. The default restart-count limit is three.

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Caution After the restart count limit has been crossed, you will need to enter the clear ip route *, clear ip eigrp neighbor, or clear eigrp address-family neighbor command to restore normal peering and redistribution.

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Reset Timer

The reset timer is used to configure the router to reset the restart count to 0 after the default or configured reset-time period has expired. This timer is designed to provide administrator with control over long-and medium-term accumulated penalties. The default reset-time period is 15 minutes.

Dampening Mechanism

The dampening mechanism is used to apply an exponential decay penalty to the restart-time period each time the maximum-prefix limit is exceeded. The half-life for the decay penalty is 150 percent of the default or user-defined restart-time value in minutes. This mechanism is designed to identify and suppress unstable peers. It is disabled by default.

How to Configure the Maximum-Prefix Limit

•Configuring the Maximum Number of Prefix Accepted from Peering Sessions: Autonomous System Configuration (required)

•Configuring the Maximum Number of Prefixes Accepted from Peering Sessions: Named Configuration (required)

•Configuring the Maximum Number of Prefixes Learned Through Redistribution: Autonomous System Configuration (required)

•Configuring the Maximum Number of Prefixes Learned Through Redistribution: Named Configuration (required)

•Configuring the Maximum-Prefix Limit for an EIGRP Process: Autonomous System Configuration (required)

•Configuring the Maximum-Prefix Limit for an EIGRP Process: Named Configuration (required)

Configuring the Maximum Number of Prefix Accepted from Peering Sessions: Autonomous System Configuration

The maximum-prefix limit can be configured for all peering sessions or individual peering sessions with the neighbor maximum-prefix (EIGRP) command. When the maximum-prefix limit is exceeded, the session with the remote peer is torn down and all routes learned from the remote peer are removed from the topology and routing tables. The maximum-prefix limit that can be configured is limited only by the available system resources on the router.

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Note In EIGRP, neighbor commands have been used traditionally to configure static neighbors. In the context of this feature, however, the neighbor maximum-prefix command can be used to configure the maximum-prefix limit for both statically configured and dynamically discovered neighbors.

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Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

•VRFs have been created and configured.

•EIGRP peering is established through the MPLS VPN.

Restrictions

•This task can be configured only in IPv4 VRF address family configuration mode.

•When you configure the neighbor maximum-prefix command to protect a single peering session, only the maximum-prefix limit, the percentage threshold, the warning-only configuration options can be configured. Session dampening, restart, and reset timers are configured on a global basis.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp as-number

4. address-family ipv4 [unicast] vrf vrf-name

5. neighbor {ip-address | peer-group-name} description text

6. neighbor ip-address maximum-prefix maximum [threshold] [warning-only]

7. neighbor maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only]

8. end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp as-number Example: Router(config)# router eigrp 1	Enters router configuration mode and creates an EIGRP routing process. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [multicast][unicast] [vrf vrf-name] autonomous-system autonomous-system-number Example: Router(config-router)# address-family ipv4 vrf vrf1	Enters address family configuration mode and creates a session for the VRF.
Step 5	neighbor {ip-address | peer-group-name} description text Example: Router(config-router-af)# neighbor 172.16.2.3 description peer with example.com	(Optional) Associates a description with a neighbor.
Step 6	neighbor ip-address maximum-prefix maximum [threshold] [warning-only] Example: Router(config-router-af)# neighbor 10.0.0.1 maximum-prefix 10000 80 warning-only	Limits the number of prefixes that are accepted from the specified EIGRP neighbor.
Step 7	neighbor maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af)# neighbor maximum-prefix 10000 80 warning-only	Limits the number of prefixes that are accepted from all EIGRP neighbors.
Step 8	end Example: Router(config-router-af)# end	Exits address family configuration mode and enters privileged EXEC mode.

Troubleshooting Tips

If an individual peer or all peers have exceeded the maximum-prefix limit the same number of times as the default or user-defined restart-count value, the individual session or all sessions will need to be manually reset with the clear ip route* or clear ip eigrp neighbor command before normal peering can be reestablished.

Configuring the Maximum Number of Prefixes Accepted from Peering Sessions: Named Configuration

The maximum-prefix limit can be configured for all peering sessions or individual peering sessions with the neighbor maximum-prefix (EIGRP) command. When the maximum-prefix limit is exceeded, the session with the remote peer is torn down and all routes learned from the remote peer are removed from the topology and routing tables. The maximum-prefix limit that can be configured is limited only by the available system resources on the router.

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Note In EIGRP, neighbor commands have been used traditionally to configure static neighbors. In the context of this feature, however, the neighbor maximum-prefix command can be used to configure the maximum-prefix limit for both statically configured and dynamically discovered neighbors.

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Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

•VRFs have been created and configured.

•EIGRP peering is established through the MPLS VPN.

Restrictions

•This task can be configured only in IPv4 VRF address family configuration mode.

•When you configure the neighbor maximum-prefix command to protect a single peering session, only the maximum-prefix limit, the percentage threshold, and the warning-only configuration options can be configured. Session dampening, restart, and reset timers are configured on a global basis.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp virtual-instance-name

4. address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number

5. neighbor {ip-address | peer-group-name} description text

6. neighbor ip-address maximum-prefix maximum [threshold] [warning-only]

7. neighbor maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | [warning-only]]

8. exit-address-family

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp virtual-instance-name Example: Router(config)# router eigrp virtual-name1	Enters router configuration mode and creates an EIGRP routing process. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number Example: Router(config-router)# address-family ipv4 vrf RED autonomous-system 45000	Enters address family configuration mode and creates a session for the VRF.
Step 5	neighbor {ip-address | peer-group-name} description text Example: Router(config-router-af)# neighbor 172.16.2.3 description peer with example.com	(Optional) Associates a description with a neighbor.
Step 6	neighbor ip-address maximum-prefix maximum [threshold][warning-only] Example: Router(config-router-af)# neighbor 10.0.0.1 maximum-prefix 10000 80 warning-only	Limits the number of prefixes that are accepted from the specified EIGRP neighbor.
Step 7	neighbor maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af)# neighbor maximum-prefix 10000 80 warning-only	Limits the number of prefixes that are accepted from all EIGRP neighbors.
Step 8	exit-address-family Example: Router(config-router-af)# exit-address-family	Exits address family configuration mode.

Troubleshooting Tips

If an individual peer or all peers have exceeded the maximum-prefix limit the same number of times as the default or user-defined restart-count value, the individual session or all sessions will need to be manually reset with the clear ip route* or clear eigrp address-family neighbors command before normal peering can be reestablished.

Configuring the Maximum Number of Prefixes Learned Through Redistribution: Autonomous System Configuration

The maximum-prefix limit can be configured for prefixes learned through redistribution with the redistribute maximum-prefix (EIGRP) command. When the maximum-prefix limit is exceeded, all routes learned from the RIB will be discarded and redistribution will be suspended for the default or user-defined time period. The maximum-prefix limit that can be configured for redistributed prefixes is limited only by the available system resources on the router.

Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

•VRFs have been created and configured.

•EIGRP peering is established through the MPLS VPN.

Restrictions

This task can be configured only in IPv4 VRF address family configuration mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp as-number

4. address-family ipv4 [unicast] vrf vrf-name

5. redistribute maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only]

6. end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp as-number Example: Router(config)# router eigrp 1	Enters router configuration mode and creates an EIGRP routing process. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [unicast] vrf vrf-name Example: Router(config-router)# address-family ipv4 vrf VRF1	Enters address family configuration mode and creates a session for the VRF.
Step 5	redistribute maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af)# redistribute maximum-prefix 10000 80 reset-time 10 restart 2	Limits the number of prefixes redistributed into an EIGRP process.
Step 6	end Example: Router(config-router-af)# end	Exits address family configuration mode and enters privileged EXEC mode.

Troubleshooting Tips

If the maximum-prefix limit has been exceeded for redistribution the same number of times as the default or user-defined restart-count value, the clear ip route * or clear ip eigrp neighbors command will need to be entered before normal redistribution will occur.

Configuring the Maximum Number of Prefixes Learned Through Redistribution: Named Configuration

The maximum-prefix limit can be configured for prefixes learned through redistribution with the redistribute maximum-prefix (EIGRP) command. When the maximum-prefix limit is exceeded, all routes learned from the RIB will be discarded and redistribution will be suspended for the default or user-defined time period. The maximum-prefix limit that can be configured for redistributed prefixes is limited only by the available system resources on the router.

Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

VRFs have been created and configured. EIGRP peering is established through the MPLS VPN.

Restrictions

This task can be configured only in IPv4 VRF address family topology configuration mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp virtual-instance-name

4. address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number

5. network ip-address [wildcard-mask]

6. topology {base | topology-name tid number}

7. redistribute maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only]

8. exit-af-topology

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp virtual-instance-name Example: Router(config)# router eigrp virtual-name1	Enters router configuration mode and creates an EIGRP routing process. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number Example: Router(config-router)# address-family ipv4 vrf VRF1	Enters address family configuration mode and creates a session for the VRF.
Step 5	network ip-address [wildcard-mask] Example: Router(config-router-af)# network 172.16.0.0	Specifies the network for an EIGRP address family routing process.
Step 6	topology {base | topology-name tid number} Example: Router(config-router-af)# topology base	Configures an EIGRP process to route traffic under the specified topology instance and enters address-family topology configuration mode.
Step 7	redistribute maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af-topology)# redistribute maximum-prefix 10000 80 reset-time 10 restart 2	Limits the number of prefixes redistributed into an EIGRP process.
Step 8	exit-af-topology Example: Router(config-router-af-topology)# exit-af-topology	Exits address family topology configuration mode.

Troubleshooting Tips

If the maximum-prefix limit has been exceeded for redistribution the same number of times as the default or user-defined restart-count value, the clear ip route * or clear eigrp address-family neighbors command will need to be entered before normal redistribution will occur.

Configuring the Maximum-Prefix Limit for an EIGRP Process: Autonomous System Configuration

The maximum-prefix limit can be configured for an EIGRP process to limit the number prefixes that are accepted from all sources. This task is configured with the maximum-prefix command. When the maximum-prefix limit is exceeded, sessions with the remote peers are brought down and all routes learned from remote peers are removed from the topology and routing tables. Also, all routes learned from the RIB are discarded and redistribution is suspended for the default or user-defined time period.

Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

•VRFs have been created and configured.

•EIGRP peering is established through the MPLS VPN.

Restrictions

This task can be configured only in IPv4 VRF address family configuration mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp as-number

4. address-family ipv4 [unicast] vrf vrf-name

5. maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only]

6. end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp as-number Example: Router(config)# router eigrp 1	Enters router configuration mode and creates an EIGRP routing process. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [unicast] vrf vrf-name Example: Router(config-router)# address-family ipv4 vrf RED	Enters address family configuration mode and creates a session for the VRF.
Step 5	maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af)# maximum-prefix 10000 80 reset-time 10 restart 2 warning-only	Limits the number of prefixes that are accepted under an address family by an EIGRP process. •The example configures a maximum-prefix limit of 10,000 prefixes, a reset time period of 10 minutes, a warning message to be displayed at 80 percent of the maximum-prefix limit, and a restart time period of 2 minutes.
Step 6	end Example: Router(config-router-af)# end	Exits address-family configuration mode and enters privileged EXEC mode.

Troubleshooting Tips

If the maximum-prefix limit has been exceeded for redistribution the same number of times as the default or user-defined restart-count value, the clear ip route * or clear ip eigrp neighbors command will need to be entered before normal redistribution will occur.

Configuring the Maximum-Prefix Limit for an EIGRP Process: Named Configuration

The maximum-prefix limit can be configured for an EIGRP process to limit the number prefixes that are accepted from all sources. This task is configured with the maximum-prefix command. When the maximum-prefix limit is exceeded, sessions with the remote peers are brought down and all routes learned from remote peers are removed from the topology and routing tables. Also, all routes learned from the RIB are discarded and redistribution is suspended for the default or user-defined time period.

Inherited Timer Values

Default or user-defined restart, restart-count, and reset-time values for the process-level configuration of this feature, configured with the maximum-prefix command, are inherited by the redistribute maximum-prefix and neighbor maximum-prefix command configurations by default. If a single peer is configured with the neighbor maximum-prefix command, a process-level configuration or a configuration that is applied to all neighbors will be inherited.

Prerequisites

•VRFs have been created and configured.

•EIGRP peering is established through the MPLS VPN.

Restrictions

This task can be configured only in IPv4 VRF address family topology configuration mode.

SUMMARY STEPS

1. enable

2. configure terminal

3. router eigrp virtual-instance-name

4. address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number

5. topology {base | topology-name tid number}

6. maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only]

7. exit-af-topology

8. show eigrp address-family {ipv4 | ipv6} [vrf vrf-name] [autonomous-system-number] [multicast] accounting

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router eigrp virtual-instance-name Example: Router(config)# router eigrp virtual-name1	Creates an EIGRP routing process and enters router configuration mode. •A maximum of 30 EIGRP routing processes can be configured.
Step 4	address-family ipv4 [multicast] [unicast] [vrf vrf-name] autonomous-system autonomous-system-number Example: Router(config-router)# address-family ipv4 vrf VRF1 autonomous-system 45000	Enters address family configuration mode and creates a session for the VRF.
Step 5	topology {base | topology-name tid number} Example: Router(config-router-af)# topology base	Configures an EIGRP process to route traffic under the specified topology instance and enters address family topology configuration mode.
Step 6	maximum-prefix maximum [threshold] [[dampened] [reset-time minutes] [restart minutes] [restart-count number] | warning-only] Example: Router(config-router-af-topology)# maximum- prefix 10000 80 reset-time 10 restart 2 warning-only	Limits the number of prefixes that are accepted under an address family by an EIGRP process. •The example configures a maximum-prefix limit of 10,000 prefixes, a reset time period of 10 minutes, a warning message to be displayed at 80 percent of the maximum-prefix limit, and a restart time period of 2 minutes.
Step 7	exit-af-topology Example: Router(config-router-af-topology)# exit-af-topology	Exits address family topology configuration mode.
Step 8	show eigrp address-family {ipv4 | ipv6} [vrf vrf-name] [autonomous-system-number] [multicast] accounting Example: Router# show eigrp address-family ipv4 22 accounting	(Optional) Displays prefix accounting information for EIGRP processes. Note Connected and summary routes are not listed individually in the output from this show command but are counted in the total aggregate count per process.

Troubleshooting Tips

If the maximum-prefix limit has been exceeded for redistribution the same number of times as the default or user-defined restart-count value, the clear ip route * or clear eigrp address-family neighbors command will need to be entered before normal redistribution will occur.

Examples

The following is sample output from the show eigrp address-family accounting command:

Router# show eigrp address-family ipv4 22 accounting 

EIGRP-IPv4 VR(saf) Accounting for AS(22)/ID(10.0.0.1) 

Total Prefix Count: 3  States: A-Adjacency, P-Pending, D-Down 

State Address/Source    Interface       Prefix   Restart  Restart/ 

                                        Count     Count   Reset(s) 

 A    10.0.0.2          Et0/0               2         0        0

 P    10.0.2.4          Se2/0               0         2        114

 D    10.0.1.3          Et0/0               0         3        0 

Configuration Examples for Configuring the Maximum-Prefix Limit

•Example: Configuring the Maximum-Prefix Limit for a Single Peer—Autonomous System Configuration

•Example: Configuring the Maximum-Prefix Limit for a Single Peer—Named Configuration

•Example: Configuring the Maximum-Prefix Limit for All Peers—Autonomous System Configuration

•Example: Configuring the Maximum-Prefix Limit for All Peers—Named Configuration

•Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Autonomous System Configuration

•Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Named Configuration

•Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Autonomous System Configuration

•Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Named Configuration

Example: Configuring the Maximum-Prefix Limit for a Single Peer—Autonomous System Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for a single peer. The maximum limit is set to 1000 prefixes, and the warning threshold is set to 80 percent. When the maximum-prefix limit is exceeded, the session with this peer will be torn down, all routes learned from this peer will be removed from the topology and routing tables, and this peer will be placed in a penalty state for 5 minutes (default penalty value).

Router(config)# router eigrp 100

Router(config-router)# address-family ipv4 vrf VRF1

Router(config-router-af)# neighbor 10.0.0.1 maximum-prefix 1000 80 

Router(config-router-af)# end

Example: Configuring the Maximum-Prefix Limit for a Single Peer—Named Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for a single peer. The maximum limit is set to 1000 prefixes, and the warning threshold is set to 80 percent. When the maximum-prefix limit is exceeded, the session with this peer will be torn down, all routes learned from this peer will be removed from the topology and routing tables, and this peer will be placed in a penalty state for 5 minutes (default penalty value).

Router(config)# router eigrp virtual-name1

Router(config-router)# address-family ipv4 vrf VRF1 autonomous-system 45000

Router(config-router-af)# neighbor 10.0.0.1 maximum-prefix 1000 80 

Router(config-router-af)# exit-address-family

Example: Configuring the Maximum-Prefix Limit for All Peers—Autonomous System Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for all peers. The maximum limit is set to 10,000 prefixes, the warning threshold is set to 90 percent, the restart timer is set to 4 minutes, a decay penalty is configured for the restart timer with the dampened keyword, and all timers are configured to be reset to 0 every 60 minutes. When the maximum-prefix limit is exceeded, all peering sessions will be torn down, all routes learned from all peers will be removed from the topology and routing tables, and all peers will be placed in a penalty state for 4 minutes (user-defined penalty value). A dampening exponential decay penalty will also be applied.

Router(config)# router eigrp 100

Router(config-router)# address-family ipv4 vrf VRF1

Router(config-router-af)# neighbor maximum-prefix 10000 90 dampened reset-time 60 
restart 4

Router(config-router-af)# end

Example: Configuring the Maximum-Prefix Limit for All Peers—Named Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for all peers. The maximum limit is set to 10,000 prefixes, the warning threshold is set to 90 percent, the restart timer is set to 4 minutes, a decay penalty is configured for the restart timer with the dampened keyword, and all timers are configured to be reset to 0 every 60 minutes. When the maximum-prefix limit is exceeded, all peering sessions will be torn down, all routes learned from all peers will be removed from the topology and routing tables, and all peers will be placed in a penalty state for 4 minutes (user-defined penalty value). A dampening exponential decay penalty will also be applied.

Router(config)# router eigrp virtual-name1

Router(config-router)# address-family ipv4 vrf VRF1 autonomous-system 45000

Router(config-router-af)# neighbor maximum-prefix 10000 90 dampened reset-time 60 
restart 4

Router(config-router-af)# exit-address-family

Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Autonomous System Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for routes learned through redistribution. The maximum limit is set to 5000 prefixes and the warning threshold is set to 95 percent. When the number of prefixes learned through redistribution reaches 4750 (95 percent of 5000), warning messages will be displayed in the console. Because the warning-only keyword is configured, the topology and routing tables will not be cleared and route redistribution will not be placed in a penalty state.

Router(config)# router eigrp 100

Router(config-router)# address-family ipv4 vrf VRF1

Router(config-router-af)# redistribute maximum-prefix 5000 95 warning-only 

Router(config-router-af)# end

Example: Configuring the Maximum-Prefix Limit for Redistributed Routes—Named Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for routes learned through redistribution. The maximum limit is set to 5000 prefixes and the warning threshold is set to 95 percent. When the number of prefixes learned through redistribution reaches 4750 (95 percent of 5000), warning messages will be displayed in the console. Because the warning-only keyword is configured, the topology and routing tables will not be cleared and route redistribution will not be placed in a penalty state.

Router(config)# router eigrp virtual-name1

Router(config-router)# address-family ipv4 vrf VRF1 autonomous-system 45000

Router(config-router-af)# network 172.16.0.0

Router(config-router-af)# topology base

Router(config-router-af-topology)# redistribute maximum-prefix 5000 95 warning-only 

Router(config-router-af-topology)# exit-af-topology

Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Autonomous System Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for an EIGRP process, which includes routes learned through redistribution and routes learned through EIGRP peering sessions. The maximum limit is set to 50,000 prefixes. When the number of prefixes learned through redistribution reaches 37,500 (75 percent of 50,000), warning messages will be displayed in the console.

When the maximum-prefix limit is exceeded, all peering sessions will be reset, the topology and routing tables will be cleared, and redistributed routes and all peering sessions will be placed in a penalty state.

Router(config)# router eigrp 100

Router(config-router)# address-family ipv4 vrf RED

Router(config-router-af)# maximum-prefix 50000 

Router(config-router-af)# end

Example: Configuring the Maximum-Prefix Limit for an EIGRP Process—Named Configuration

The following example, starting in global configuration mode, configures the maximum-prefix limit for an EIGRP process, which includes routes learned through redistribution and routes learned through EIGRP peering sessions. The maximum limit is set to 50,000 prefixes. When the number of prefixes learned through redistribution reaches 37,500 (75 percent of 50,000), warning messages will be displayed in the console.

When the maximum-prefix limit is exceeded, all peering sessions will be reset, the topology and routing tables will be cleared, and redistributed routes and all peering sessions will be placed in a penalty state.

Router(config)# router eigrp virtual-name

Router(config-router)# address-family ipv4 vrf VRF1 autonomous-system 45000

Router(config-router-af)# topology base

Router(config-router-af-topology)# maximum-prefix 50000 

Router(config-router-af-topology)# exit-af-topology

Additional References

Related Documents

Related Topic	Document Title
Cisco IOS commands	Cisco IOS Master Commands List, All Releases
EIGRP commands	Cisco IOS IP Routing: EIGRP Command Reference
EIGRP autonomous system configuration and EIGRP named configuration	"Configuring EIGRP" module
BGP cost community configuration tasks for EIGRP MPLS VPN PE-CE	"BGP Cost Community Support" module
Basic EIGRP configuration tasks	"Configuring EIGRP" module
EIGRP MPLS VPN configuration tasks	"EIGRP MPLS VPN PE-CE Site of Origin (SoO)" module
MPLS VPNs configuration tasks	"Configuring MPLS Layer 3 VPNs" module
System logging	"Troubleshooting and Fault Management" module of the Cisco IOS Network Management Configuration Guide

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MIBs

MIBs	MIBs Link
None	To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

RFCs

RFCs	Title
None	—

Technical Assistance

Description

Link

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Feature Information for EIGRP Prefix Limit Support

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

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Note Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

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Table 1 Feature Information for EIGRP Prefix Limit Support 

Feature Name	Releases	Feature Information
EIGRP Prefix Limit Support	12.0(29)S 12.3(14)T 15.0(1)M 12.2(33)SRE	The EIGRP Prefix Limit Support feature introduces the capability to limit the number of prefixes per VRF that are accepted from a specific peer or to limit all prefixes that are accepted by an Enhanced Interior Gateway Routing Protocol (EIGRP) process through peering and redistribution. The following commands were introduced or modified by this feature: maximum-prefix, neighbor maximum-prefix (EIGRP), redistribute maximum-prefix (EIGRP), show ip eigrp accounting, show ip eigrp vrf accounting In Cisco IOS Release 15.0(1)M and 12.2(33)SRE, the following commands were introduced or modified: maximum-prefix, neighbor description, redistribute maximum-prefix (EIGRP), show eigrp address-family accounting, show ip eigrp accounting. In Cisco IOS Release 15.0(1)M and 12.2(33)SRE, the following command was replaced: show ip eigrp vrf accounting.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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