To create or modify a label switched path (LSP) attribute list, use thempls traffic-eng lsp attributes command in global configuration mode. To remove a specified LSP attribute list from the device configuration, use the no form of this command.

Syntax Description

Command Default

An LSP attribute list is not created unless you create one.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

This command sets up an LSP attribute list and enters LSP Attributes configuration mode, in which you can enter LSP attributes.

To associate the LSP attributes and LSP attribute list with a path option for an LSP, you must configure the tunnel mpls traffic-eng path option attributes string command, where string is the identifier for the specific LSP attribute list.

An LSP attribute referenced by the path option takes precedence over the values configured on the tunnel interface. If an attribute is not specified in the LSP attribute list, the devices takes the attribute from the tunnel configuration. LSP attribute lists do not have default values. If the attribute is not configured on the tunnel, then the device uses tunnel default values.

Once you type the mpls traffic-eng lsp attributes command, you enter the LSP Attributes configuration mode where you define the attributes for the LSP attribute list that you are creating.

The mode commands are as follows:

• affinity—Specifies attribute flags for links that make up an LSP.
• auto-bw—Specifies automatic bandwidth configuration.
• bandwidth—Specifies LSP bandwidth.
• lockdown—Disables reoptimization for the LSP.
• priority—Specifies LSP priority.
• protection—Enables failure protection.
• record-route—Records the route used by the LSP.

The following monitoring and management commands are also available in the LSP Attributes configuration mode:

• exit—Exits from LSP Attributes configuration mode.
• list—Relists all the entries in the LSP attribute list.
• no—Removes a specific attribute from the LSP attribute list.

Related Commands

To configure a mesh group in an Interior Gateway Protocol (IGP) to allow Multiprotocol Label Switching (MPLS) traffic engineering (TE) label switch routers (LSRs) that belong to the same mesh group to signal tunnels to the local router, use the mpls traffic-eng mesh-group command in router configuration mode. To disable signaling of tunnels from LSRs in the same mesh group to the local router, use the no form of this command.

Syntax Description

Command Default

No tunnels are signaled for routers in the same mesh group.

Command Modes

Router configuration (config-router)#

Command History

Usage Guidelines

Use this command to configure a mesh group in an IGP. This allows the MPLS TE LSRs that belong to the specified mesh group to signal tunnels to the local router. The IGP floods mesh group configuration to all routers belonging to the same mesh group. An autotemplate determines how a router participates in an autotunnel. A router can participate in a mesh group through two-way tunnels or one-way tunnels.

Open Shortest Path First (OSPF) is the only IGP supported for the MPLS Traffic Engineering--AutoTunnel Mesh Groups feature.

Related Commands

To configure a router running Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF) so that Protocol-Independent Multicast (PIM) and Multiprotocol Label Switching (MPLS) traffic engineering (TE) can work together, use the mpls traffic-eng multicast-intact command in router configuration mode. To disable interoperability between PIM and MPLS TE, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

PIM and MPLS TE do not work together.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

The mpls traffic-eng multicast-intact command allows PIM to use the native hop-by-hop neighbors while unicast routing is using MPLS TE tunnels.

This command works only for OSPF and IS-IS protocols.

Related Commands

To configure a link as a passive interface between two Autonomous System Boundary Routers (ASBRs), use the mpls traffic-eng passive-interface command in interface configuration mode. To disable the passive link, use the no form of this command.

Syntax Description

Command Default

None

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

The mpls traffic-eng passive-interface command sets the next-hop address for a passive interface. The command is required only for a broadcast link.

Enter the mpls traffic-eng passive-interface command only on the outgoing interface on which the label-switched path (LSP) will exit; you do not have to enter this command on both ends of the interautonomous system (Inter-AS) link.

On a point-to-point link or on a multiaccess link where there is only one neighbor, you do not have to enter the isis or ospf keyword (or the sysid argument).

If two autonomous systems use different IGPs and have more than one neighbor on the link, you must enter the nbr-igp-id keyword followed by isis or ospf and the sysid. The sysid must be unique for each neighbor.

For a broadcast link (that is, other Resource Reservation Protocol (RSVP)) features are using the passive link), you must enter the nbr-if-addr keyword.

For an RSVP Hello configuration on an Inter-AS link, all keywords are required.

To configure a path option list, use the mpls traffic-eng path-option list command in global configuration mode. To disable this function, use the no form of this command.

Syntax Description

Command Default

There are no path option lists.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

A path option list contains a list of backup paths for a primary path option. You can specify a path option list by entering its name or identifier.

After you enter the mpls traffic-eng path-option list command, the router enters path option list configuration mode and you can enter the following commands:

• path-option --Specifies the name or identification number of the next path option to add, edit, or delete.
• list --Lists all path options.
• no --Deletes a specified path option.
• exit --Exits from path option list configuration mode.

Then you can specify explicit backup paths by entering their name or identifier.

Related Commands

To specify the metric type to use for path selection for tunnels for which the metric type has not been explicitly configured, use the mpls traffic-eng path-selection metric command in global configuration mode. To remove the specified metric type, use the no form of this command.

Syntax Description

Command Default

The default is the te metric.

Command Modes

Global configuration

Command History

Usage Guidelines

Use this command to specify the metric type to be used for traffic engineering (TE) tunnels for which the tunnel mpls traffic-eng path-selection metric command has not been specified.

The metric type to be used for path calculation for a given tunnel is determined as follows:

• If the tunnel mpls traffic-eng path-selection metric command was entered to specify a metric type for the tunnel, use that metric type.
• Otherwise, if the mpls traffic-eng path-selection metric was entered to specify a metric type, use that metric type.
• Otherwise, use the default (te) metric.

Related Commands

To force immediate reoptimization of all traffic engineering tunnels, use the mpls traffic-eng reoptimize command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To turn on automatic reoptimization of Multiprotocol Label Switching (MPLS) traffic engineering when certain events occur, such as when an interface becomes operational, use the mpls traffic-eng reoptimize events command in global configuration mode. To disable automatic reoptimization, use the no form of this command.

Syntax Description

Command Default

Event-based reoptimization is disabled.

Command Modes

Global configuration (config)

Command History

Related Commands

To delay the removal of old label switched paths (LSPs) or installation of new LSPs after tunnel reoptimization, use the mpls traffic-eng reoptimize timers delay command in global configuration mode. To restore the default value, use the no form of this command.

Syntax Description

Command Default

Removal of old LSPs and installation of new LSPs is not delayed.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

A device with Multiprotocol Label Switching traffic engineering (MPLS-TE) tunnels periodically examines tunnels with established LSPs to discover if more efficient LSPs (paths) are available. If a better LSP is available, the device signals the more efficient LSP. If the signaling is successful, the device replaces the older LSP with the new, more efficient LSP.

Sometimes, the slower router-point nodes may not utilize the new label’s forwarding plane. In this case, if the headend node replaces the labels quickly, packet loss can occur. The packet loss is avoided by delaying the cleanup of the old LSP by using the mpls traffic-eng reoptimize timers delay cleanup command. Until the cleanup of the old LSP is performed, subsequent reoptimizations for the tunnel are prevented.

Related Commands

To control the frequency with which tunnels with established label switched paths (LSPs) are checked for better LSPs, use the mpls traffic-eng reoptimize timers frequency command in global configuration mode. To disable this function, use the no form of this command.

Syntax Description

Command Default

3600 seconds (1 hour)

Command Modes

Global configuration (config)

Command History

Usage Guidelines

A device with traffic engineering tunnels periodically examines tunnels with established LSPs to learn if better LSPs are available. If a better LSP seems to be available, the device attempts to signal the better LSP; if the signaling is successful, the device replaces the old, inferior LSP with the new, better LSP.

Note	If the lockdown keyword is specified with the tunnel mpls traffic-eng path-option command, then a reoptimize check is not done on the tunnel.

If you configure a traffic engineering tunnel with an explicit path that is not fully specified (a series of router IDs or a combination of router IDs and interface addresses), then reoptimization may not occur.

Note	If you specify a low reoptimization frequency (for example, less than 30 seconds), there may be an increase in CPU utilization for configurations with a large number of traffic engineering tunnels.

Related Commands

To specify that the traffic engineering router identifier for the node is the IP address associated with a given interface, use the mpls traffic-eng router-id command in router configuration mode. To remove the traffic engineering router identifier, use the no form of this command.

Syntax Description

Command Default

No traffic engineering router identifier is specified.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

This router identifier acts as a stable IP address for the traffic engineering configuration. This IP address is flooded to all nodes. For all traffic engineering tunnels originating at other nodes and ending at this node, you must set the tunnel destination to the traffic engineering router identifier of the destination node, because that is the address that the traffic engineering topology database at the tunnel head uses for its path calculation.

You should configure the same traffic engineering router id for all Interior Gateway Protocol (IGP) routing processes.

Related Commands

To specify how often Intermediate System-to-Intermediate System (IS-IS) extracts traffic engineering type, length, values (TLVs) objects from flagged label switched paths (LSPs) and passes them to the traffic engineering topology database, and the maximum number of LSPs that the router can process immediately, use the mpls traffic-eng scanner command in router configuration mode. To disable the frequency that IS-IS extracts traffic engineering TLVs and the maximum number of LSPs IS-IS passes to the traffic engineering topology database, use the no form of this command.

Syntax Description

Command Default

IS-IS sends traffic engineering TLVs into the traffic engineering topology database every 5 seconds after the first 15 LSPs are processed.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

When IS-IS receives a new LSP, it inserts it into the IS-IS database. If the LSP contains traffic engineering TLVs, IS-IS flags the LSPs for transmission to the traffic engineering database. Depending on the default or user-specified interval, traffic engineering TLVs are extracted and sent to the traffic engineering database. Users can also specify the maximum number of LSPs that the router can process immediately. Processing entails checking for traffic engineering TLVs, extracting them, and passing them to the traffic engineering database. If more than 50 LSPs need to be processed, there is a delay of 5 seconds for subsequent LSPs.

The first 15 LSPs are sent without a delay into the traffic engineering database. If more LSPs are received, the default delay of 5 seconds applies.

If you specify the no form of this command, there is a delay of 5 seconds before IS-IS scans its database and passes traffic engineering TLVs associated with flagged LSPs to the traffic engineering database

Related Commands

Note

Effective with Cisco IOS Release 15.2(2)S, the mpls traffic-eng signalling advertise implicit-null command is deprecated by the mpls traffic-eng signalling advertise explicit-null command because the IOS MPLS-TE tail router now advertises the implicit-null label in signaling messages sent to neighbors by default. Prior to this release, the IOS MPLS-TE tail router advertised the explicit-null label by default.

To configure the MPLS-TE tail router to override the new default (implicit-null label) to use the MPLS encoding for the explicit-null label in signaling messages advertised to neighbors, use the mpls traffic-eng signalling advertise explicit-null command in global configuration mode. To disable this feature, use the no form of this command.

Syntax Description

Command Default

The IOS MPLS-TE tail router now advertises the implicit-null label in signaling messages sent to neighbors.

Command Modes

Global configuration (config)#

Command History

Usage Guidelines

If the mpls traffic-eng signalling advertise implicit-null command exists your configuration we recommend that you remove it from your configuration.

The mpls traffic-eng signalling advertise explicit-null command is used on an IOS or IOS-XE MPLS-TE tail router to advertise explicit-null label in signaling messages. If the mpls traffic-eng signalling advertise explicit-null command is not configured, an implicit-null label (IETF label 3) is advertised in signaling messages.

Note

Effective with Cisco IOS Release 15.2(2)S, the mpls traffic-eng signalling advertise implicit-null command is deprecated by the mpls traffic-eng signalling advertise explicit-null command because the IOS MPLS-TE tail router now advertises the implicit-null label in signaling messages sent to neighbors by default. Prior to this release, the IOS MPLS-TE tail router advertised the explicit-null label by default. See the mpls traffic-eng signalling advertise explicit-null command if you want to configure the IOS MPLS-TE tail router to override the new default (implicit-null label) and advertise the explicit-null label to neighbors instead.

To use MPLS encoding for the implicit-null label in signaling messages sent to neighbors, use the mpls traffic-eng signalling advertise implicit-null command in global configuration mode. To disable this feature, use the no form of this command.

Syntax Description

Command Default

None

Command Modes

Global configuration (config)#

Command History

Usage Guidelines

The mpls traffic-eng signalling advertise implicit-null command is typically used on an IOS MPLS-TE tail router to advertise the IETF implicit-null label "3" signalling message to an non-IOS router.

To configure the Shared Risk Link Group (SRLG) membership of a link (interface), use the mpls traffic-eng srlg command in interface configuration mode. To remove a link from membership of one or more SRLGs, use the no form of this command.

Syntax Description

Command Default

A link does not have membership in any SRLG.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

You can enter the mpls traffic-eng srlg command multiple times to make a link a member of multiple SRLGs.

Related Commands

To specify the amount of time that a router ignores a link in its traffic engineering topology database in tunnel path Constrained Shortest Path First (CSPF) computations following a traffic engineering tunnel error on the link, use the mpls traffic-eng topology holddown sigerr command in global configuration mode. To disable the time set to ignore a ink following a traffic engineering tunnel error on the link, use the no form of this command.

Syntax Description

Command Default

If you do not specify this command, tunnel path calculations ignore a link on which there is a traffic engineering error until either 10 seconds have elapsed or a topology update is received from the Interior Gateway Protocol (IGP).

Command Modes

Global configuration (config)

Command History

Usage Guidelines

A router that is at the headend for traffic engineering tunnels might receive a Resource Reservation Protocol (RSVP) No Route error message for an existing tunnel or for one being signaled due to the failure of a link the tunnel traffic traverses before the router receives a topology update from the IGP routing protocol announcing that the link is down. In such a case, the headend router ignores the link in subsequent tunnel path calculations to avoid generating paths that include the link and are likely to fail when signaled. The link is ignored until the router receives a topology update from its IGP or a link hold-down timeout occurs. You can use the mpls traffic-eng topology holddown sigerr command to change the link hold-down time from its 10-second default value.

Related Commands

To enable Multiprotocol Label Switching (MPLS) traffic engineering tunnel signaling on a device, use the mpls traffic-eng tunnels command in global configuration mode. To disable MPLS traffic engineering tunnel signaling, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

The command is disabled.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

This command enables MPLS traffic engineering on a device. For you to use the feature, MPLS traffic engineering must also be enabled on the desired interfaces.

Related Commands

To enable Multiprotocol Label Switching (MPLS) traffic engineering (TE) tunnel signaling on an interface (assuming that it is enabled on the device), use the mpls traffic-eng tunnels command in interface configuration mode. To disable MPLS traffic engineering tunnel signaling on the interface, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

The MPLS TE is disabled on all interfaces.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Before you enable MPLS TE on the interface, you must enable MPLS TE on the device. An enabled interface has its resource information flooded into the appropriate Interior Gateway Protocol (IGP) link-state database and accepts traffic engineering tunnel signaling requests.

You can use this command to enable MPLS traffic engineering on an interface, thereby eliminating the need to use the ip rsvp bandwidth command. However, if your configuration includes Call Admission Control (CAC) for IPv4 Resource Reservation Protocol (RSVP) flows, you must use the ip rsvp bandwidth rsvp bandwidth command.

Related Commands

To specify standard Multiprotocol Label Switching (MPLS) tagging, use the mpls ttl-dec command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Optimized MPLS tagging (no mpls ttl-dec).

Command Modes

Global configuration (config)

Command History

Usage Guidelines

In Cisco IOS Release 12.2(18)SXE and later releases, MPLS tagging has been optimized to allow the rewriting of the original packet’s IP type of service (ToS) and Time to Live (TTL) values before the MPLS label is pushed onto the packet header. This change can result in a slightly lower performance for certain types of traffic. If the packet’s original ToS/TTL values are not significant, you enter the mpls ttl-dec command for standard MPLS tagging.

Related Commands

To adjust the maximum packet size or maximum transmission unit (MTU) size, use the mtu command in interface configuration mode, connect configuration mode, or xconnect subinterface configuration mode. To restore the MTU value to its original default value, use the no form of this command.

Syntax Description

Command Default

The table below lists default MTU values according to media type.

Command Modes

Interface configuration (config-if)
Connect configuration (xconnect-conn-config)
xconnect subinterface configuration (config-if-xconn)

Command History

Usage Guidelines

Each interface has a default maximum packet size or MTU size. This number generally defaults to the largest size possible for that interface type. On serial interfaces, the MTU size varies but cannot be set to a value less than 64 bytes.

Note	The connect configuration mode is used only for Frame Relay Layer 2 interworking.

Changing the MTU Size

Changing the MTU size is not supported on a loopback interface.

Changing the MTU size on a Cisco 7500 series router results in the recarving of buffers and resetting of all interfaces. The following message is displayed: RSP-3-Restart:cbus complex .

You can configure native Gigabit Ethernet ports on the Cisco 7200 series router to a maximum MTU size of 9216 bytes. The MTU values range from 1500 to 9216 bytes. The MTU values can be configured to any range that is supported by the corresponding main interface.

MTU Size for an IPSec Configuration

In an IPSec configuration, such as in a crypto environment, an MTU value that is less than 256 bytes is not accepted. If you configure an MTU value less than 256 bytes, then the MTU value is automatically overwritten and given a value of 256 bytes.

Protocol-Specific Versions of the mtu Command

Changing the MTU value with the mtu interface configuration command can affect values for the protocol-specific versions of the command (the ip mtu command, for example). If the value specified with the ip mtu interface configuration command is the same as the value specified with the mtu interface configuration command, and you change the value for the mtu interface configuration command, the ip mtu value automatically matches the new mtu interface configuration command value. However, changing the values for the ip mtu configuration commands has no effect on the value for the mtu interface configuration command.

ATM and LANE Interfaces

ATM interfaces are not bound by what is configured on the major interface. By default, the MTU on a subinterface is equal to the default MTU (4490 bytes). A client is configured with the range supported by the corresponding main interface. The MTU can be changed on subinterfaces, but it may result in recarving of buffers to accommodate the new maximum MTU on the interface.

VRF-Aware Service Infrastructure Interfaces

The mtu command does not support the VRF-Aware Service Infrastructure (VASI) type interface.

Cisco 7600 Valid MTU Values

On the Cisco 7600 platform, the following valid values are applicable:

• For the SVI ports: from 64 to 9216 bytes
• For the GE-WAN+ ports: from 1500 to 9170 bytes
• For all other ports: from 1500 to 9216 bytes

You can receive jumbo frames on access subinterfaces also. The MTU values can be configured to any range that is supported by the corresponding main interface. If you enable the jumbo frames, the default is 64 bytes for the SVI ports and 9216 bytes for all other ports. The jumbo frames are disabled by default.

Cisco uBR10012 Universal Broadband Router

While configuring the interface MTU size on a Gigabit Ethernet SPA on a Cisco uBR10012 router, consider the following guidelines:

• The default interface MTU size accommodates a 1500-byte packet, plus 22 additional bytes to cover the following overhead:
  • Layer 2 header--14 bytes
  • Dot1Q header--4 bytes
  • CRC--4 bytes
• If you are using MPLS, be sure that the mpls mtu command is configured with a value less than or equal to the interface MTU.
• If you are using MPLS labels, you should increase the default interface MTU size to accommodate the number of MPLS labels. Each MPLS label adds 4 bytes of overhead to a packet.

Note	For the Gigabit Ethernet SPAs on the Cisco uBR10012 router, the default MTU size is 1500 bytes. When the interface is being used as a Layer 2 port, the maximum configurable MTU is 9000 bytes.

Related Commands

To set the name of a Multiple Spanning Tree (MST) region, use the name command in MST configuration submode. To return to the default name, use the no form of this command.

Syntax Description

Command Default

Empty string

Command Modes

MST configuration (config-mst)

Command History

Usage Guidelines

Two or more Cisco 7600 series routers with the same VLAN mapping and configuration version number are considered to be in different MST regions if the region names are different.

Caution

Be careful when using the name command to set the name of an MST region. If you make a mistake, you can put the Cisco 7600 series router in a different region. The configuration name is a case-sensitive parameter.

Related Commands

To specify the peer IP address and virtual circuit (VC) ID value of a Layer 2 VPN (L2VPN) pseudowire, use the neighbor command in interface configuration mode. To remove the peer IP address and VC ID value of an L2VPN pseudowire, use the no form of this command.

Syntax Description

Command Default

Peer address and VC ID value of a pseudowire are not specified.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

You must configure the neighbor command for the pseudowire to be functional.

Related Commands

To enable the exchange of information with a Border Gateway Protocol (BGP) neighbor, use the neighbor activate command in address family configuration mode or router configuration mode. To disable the exchange of an address with a BGP neighbor, use the no form of this command.

Syntax Description

Command Default

The exchange of addresses with BGP neighbors is enabled for the IPv4 address family. Enabling address exchange for all other address families is disabled.

Note

Address exchange for address family IPv4 is enabled by default for each BGP routing session configured with the neighbor remote-as command unless you configure the no bgp default ipv4-activate command before configuring the neighbor remote-as command, or you disable address exchange for address family IPv4 with a specific neighbor by using the no neighbor activate command.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Usage Guidelines

Use this command to advertise address information in the form of an IP or IPv6 prefix. The address prefix information is known as Network Layer Reachability Information (NLRI) in BGP.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces. This keyword does not need to be used for non-link-local IPv6 addresses.

Related Commands

To configure provider edge (PE) routers to allow readvertisement of all prefixes containing duplicate autonomous system numbers (ASNs), use the neighbor allowas-in command in router configuration mode. To disable the readvertisement of the ASN of the PE router, use the no form of this command.

Syntax Description

Command Default

Readvertisement of all prefixes containing duplicate ASNs is disabled by default.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

In a hub and spoke configuration, a PE router readvertises all prefixes containing duplicate autonomous system numbers. Use the neighbor allowas-in command to configure two VRFs on each PE router to receive and readvertise prefixes are as follows:

• One Virtual Private Network routing and forwarding (VRF) instance receives prefixes with ASNs from all PE routers and then advertises them to neighboring PE routers.
• The other VRF receives prefixes with ASNs from the customer edge (CE) router and readvertises them to all PE routers in the hub and spoke configuration.

You control the number of times an ASN is advertised by specifying a number from 1 to 10.

Related Commands

To configure a provider edge (PE) router to override the autonomous system number (ASN) of a site with the ASN of a provider, use the neighbor as-override command in router configuration mode. To remove Virtual Private Network (VPN) IPv4 prefixes from a specified router, use the no form of this command.

Syntax Description

Command Default

Automatic override of the ASN is disabled.

Command Modes

Router configuration

Command History

Usage Guidelines

This command is used in conjunction with the site-of-origin feature, identifying the site where a route originated, and preventing routing loops between routers within a VPN.

Related Commands

To configure the Exterior Border Gateway Protocol (eBGP) peer router, which is the neighboring Autonomous System Boundary Router (ASBR), as an Inter-AS Option AB peer, use the neighbor inter-as-hybrid command in address family configuration mode. The Inter-AS Option AB feature is a hybrid of Inter-AS Option (10)A and Inter-AS Option (10)B network configurations, enabling the interconnection of different autonomous systems to provide Virtual Private Network (VPN) services. To remove the peer router configuration, use the no form of this command.

Syntax Description

Command Default

No Inter-AS AB neighbor eBGP (ASBR) router is specified.

Command Modes

Address family configuration (config-router-af)

Command History

Usage Guidelines

Advertised routes have the route targets (RTs) that are configured on the virtual private network (VPN) routing and forwarding (VRF) instance. Advertised routes do not have their original RTs.

If any prefixes are imported into Option AB VRFs, then the imported paths are advertised to this peer.

Related Commands

To enable the IPv6 address family for a Border Gateway Protocol (BGP) neighbor that does not support capability negotiation, use the neighbor override-capability-negcommand in address family configuration mode. To disable the IPv6 address family for a BGP neighbor that does not support capability negotiation, use the no form of this command.

Syntax Description

Command Default

Capability negotiation is enabled.

Command Modes

Address family configuration

Command History

Usage Guidelines

Capability negotiation is used to establish a connection between BGP-speaking peers. If one of the BGP peers does not support capability negotiation, the connection is automatically terminated. The neighbor override-capability-negcommand overrides the capability negotiation process and enables BGP-speaking peers to establish a connection.

The neighbor override-capability-negcommand is supported only in address family configuration mode for the IPv6 address family.

Related Commands

To add an entry to the BGP or multiprotocol BGP neighbor table, use the neighbor remote-as command in router configuration mode. To remove an entry from the table, use the no form of this command.

Syntax Description

Command Default

There are no BGP or multiprotocol BGP neighbor peers.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

Specifying a neighbor with an autonomous system number that matches the autonomous system number specified in the router bgp global configuration command identifies the neighbor as internal to the local autonomous system. Otherwise, the neighbor is considered external.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

By default, neighbors that are defined using the neighbor remote-as command in router configuration mode exchange only unicast address prefixes. To exchange other address prefix types, such as multicast and Virtual Private Network (VPN) Version 4, neighbors must also be activated in the appropriate address family configuration mode.

Use the alternate-as keyword introduced in Cisco IOS Release 12.2(33)SXH to specify up to five alternate autonomous systems in which a dynamic BGP neighbor may be identified. BGP dynamic neighbor support allows BGP peering to a group of remote neighbors that are defined by a range of IP addresses. BGP dynamic neighbors are configured using a range of IP addresses and BGP peer groups. After a subnet range is configured and associated with a BGP peer group using the bgp listen command and a TCP session is initiated for an IP address in the subnet range, a new BGP neighbor is dynamically created as a member of that group. The new BGP neighbor will inherit any configuration or templates for the group.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces. This keyword does not need to be used for non-link-local IPv6 addresses.

In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain--65538 for example--as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, the Cisco implementation of 4-byte autonomous system numbers uses asdot--1.2 for example--as the only configuration format, regular expression match, and output display, with no asplain support.

Note	In Cisco IOS releases that include 4-byte ASN support, command accounting and command authorization that include a 4-byte ASN number are sent in the asplain notation irrespective of the format that is used on the command-line interface.

To ensure a smooth transition, we recommend that all BGP speakers within an autonomous system that is identified using a 4-byte autonomous system number, be upgraded to support 4-byte autonomous system numbers.

Related Commands

To specify that a communities attribute should be sent to a BGP neighbor, use the neighbor send-community command in address family or router configuration mode. To remove the entry, use the no form of this command.

Syntax Description

Command Default

No communities attribute is sent to any neighbor.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Usage Guidelines

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

Related Commands

To enable a Border Gateway Protocol (BGP) router to send Multiprotocol Label Switching (MPLS) labels with BGP routes to a neighboring BGP router, use the neighbor send-label command in address family configuration mode or router configuration mode. To disable this feature, use the no form of this command.

Syntax Description

Command Default

BGP routers distribute only BGP routes.

Command Modes

Address family configuration (config-router-af)
Router configuration (config-router)

Command History

Usage Guidelines

The neighbor send-label command enables a router to use BGP to distribute MPLS labels along with IPv4 routes to a peer router. You must issue this command on both the local and the neighboring router.

This command has the following restrictions:

• If a BGP session is running when you issue the neighbor send-label command, the BGP session flaps immediately after the command is issued.
• In router configuration mode, only IPv4 addresses are distributed.

Use the neighbor send-label command in address family configuration mode, to bind and advertise IPv6 prefix MPLS labels. Using this command in conjunction with the mpls ipv6 source-interface global configuration command allows IPv6 traffic to run over an IPv4 MPLS network without any software or hardware configuration changes in the backbone. Edge routers configured to run both IPv4 and IPv6 traffic forward IPv6 traffic using MPLS and multiprotocol internal BGP (MP-iBGP).

Cisco IOS software installs /32 routes for directly connected external BGP (eBGP) peers when the BGP session for such a peer comes up. The /32 routes are installed only when MPLS labels are exchanged between such peers. Directly connected eBGP peers exchange MPLS labels for:

• IP address families (IPv4 and IPv6) with the neighbor send-label command enabled for the peers
• VPN address families (VPNv4 and VPNv6)

A single BGP session can include multiple address families. If one of the families exchanges MPLS labels, the /32 neighbor route is installed for the connected peer.

Related Commands

To enable a Border Gateway Protocol (BGP) router to send Multiprotocol Label Switching (MPLS) labels with explicit-null information for a CSC-CE router and BGP routes to a neighboring CSC-PE router, use the neighbor send-label explicit-null command in address family configuration mode or router configuration mode. To disable a BGP router from sending MPLS labels with explicit-null information, use the no form of this command.

Syntax Description

Command Default

None

Command Modes

Address family configuration (config-router-af)
Router configuration (config-router)

Command History

Usage Guidelines

This command enables a CSC-CE router to use BGP to distribute MPLS labels with a value of zero for explicit-null instead of implicit-null along with IPv4 routes to a CSC-PE peer router.

You must issue this command only on the local CSC-CE router.

You can use this command only with IPv4 addresses.

Related Commands

To suppress a Virtual Private LAN Service (VPLS) signaling protocol use the neighbor suppress-signaling-protocol command in address family configuration or router configuration mode. To remove the entry, use the no form of this command.

Syntax Description

Command Default

LDP signaling is not suppressed.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Usage Guidelines

If you specify that LDP signaling is suppressed by using the ldp keyword, BGP signaling will be enabled.

Related Commands

To have the Cisco software allow Border Gateway Protocol (BGP) sessions to use any operational interface for TCP connections, use the neighbor update-source command in router configuration mode. To restore the interface assignment to the closest interface, which is called the best local address, use the no form of this command.

Syntax Description

Command Default

Best local address

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

This command can work in conjunction with the loopback interface feature described in the “Interface Configuration Overview” chapter of the Cisco IOS Interface and Hardware Component Configuration Guide.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

The neighbor update-source command must be used to enable IPv6 link-local peering for internal or external BGP sessions.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces and for these link-local IPv6 addresses you must specify the interface they are on. The syntax becomes <IPv6 local-link address>%<interface name>, for example, FE80::1%Ethernet1/0. Note that the interface type and number must not contain any spaces, and be used in full-length form because name shortening is not supported in this situation. The % keyword and subsequent interface syntax is not used for non-link-local IPv6 addresses.

Related Commands

To create pseudowires with specific provider edge (PE) routers in an L2VPN Advanced VPLS configuration, use the neighbor command in VPLS transport configuration mode. To remove the pseudowires, use the no form of this command.

Syntax Description

Command Default

Pseudowires are not created.

Command Modes

VPLS transport configuration (config-if-transport)

Command History

Usage Guidelines

The neighbor command uses default values for the VFI name, VPN ID, and encapsulation type.

Related Commands

To specify the type of tunnel signaling and encapsulation mechanism for each Virtual Private LAN Service (VPLS) peer, use the neighbor command in L2 VFI manual configuration mode. To disable a split horizon, use the no form of this command.

Syntax Description

Command Default

Split horizon is enabled.

Command Modes

L2 VFI manual configuration (config-vfi)

Command History

Usage Guidelines

In a full-mesh VPLS network, keep split horizon enabled to avoid looping.

With the introduction of VPLS Autodiscovery, the remote router ID no longer needs to be the LDP router ID. The address that you specify can be any IP address on the peer, as long as it is reachable. When VPLS Autodiscovery discovers peer routers for the VPLS, the peer router addresses might be any routable address.

Related Commands

To configure the network source of the next hop to be used by the PE VPN, use the network command in router configuration mode. To disable the source, use the no form of this command.

Syntax Description

Command Default

Next-hop network sources are not configured.

Command Modes

Address family configuration
Router configuration

Command History

Usage Guidelines

The ipv6-address argument in this command configures the IPv6 network number.

Related Commands

To specify the next IP address in the explicit path, use the next-address command in IP explicit path configuration mode.

Syntax Description

Command Default

The next IP address in the explicit path is not specified.

Command Modes

IP explicit path configuration

Command History

Usage Guidelines

To specify an explicit path that includes only the addresses specified, specify each address in sequence by using the next-address command without the loose keyword.

To configure an interarea traffic engineering (TE) tunnel, configure the tunnel path options as loose explicit paths. Specify that each Autonomous System Boundary Router (ASBR) traversed by the tunnel label switched path (LSP) is a loose hop by entering the next-address loose command.

To use explicit paths for TE tunnels within an Interior Gateway Protocol (IGP) area, you can specify a combination of both loose and strict hops.

When specifying an explicit path for an MPLS TE tunnel, you can specify link or node addresses of the next-hop routers in an explicit path. You can also specify a mixture of link and node addresses. However, there are some restrictions:

• In Cisco IOS Releases 12.2(33)SRD and 12.4(24)T, and Cisco XE Release 2.4 and earlier releases, you cannot specify an explicit path that uses a link address as the first hop and then node addresses as the subsequent hops. However, you can use a node address as the first hop andlink addresses as the subsequent hops.
• In Cisco IOS Releases after 12.2(33)SRD, 12.4(24)T , and Cisco XE Release 2.4, you can use a link address as the first hop and then node addresses as the subsequent hops. There are no restrictions when specifying a mixture of link and node addresses.

When specifying an explicit path, if you specify the “forward” address (the address of the interface that forwards the traffic to the next router) as the next-hop address, the explicit path might not be used. Using the forward address allows that entry to be treated as a loose hop for path calculation. Cisco recommends that you use the “receive”address (the address of the interface that receives traffic from the sending router) as the next-hop address.

In the following example, router R3 sends traffic to router R1. The paths marked a,b and x,y between routers R1 and R2 are parallel paths.

R1(a)----(b)R2(c)--(d)R3
  (x)----(y)

If you configure an explicit path from R3 to R1 using the “forward” addresses (addresses d and b), the tunnel might reroute traffic over the parallel path (x,y) instead of the explicit path. To ensure that the tunnel uses the explicit path, specify the “receive” addresses as part of the next-address command, as shown in the following example:

ip explicit-path name path1
  next-address ©)
  next-address (a)

Related Commands

To disable sending routing updates on an interface, use the passive-interface command in router configuration mode. To reenable the sending of routing updates, use the no form of this command.

Syntax Description

Command Default

No interfaces are passive. Routing updates are sent to all interfaces on which the routing protocol is enabled.

Command Modes

Router configuration

Command History

Usage Guidelines

If you disable the sending of routing updates on an interface, the particular address prefix will continue to be advertised to other interfaces, and updates from other routers on that interface continue to be received and processed.

The default keyword sets all interfaces as passive by default. You can then configure individual interfaces where adjacencies are desired using the no passive-interface command. The default keyword is useful in Internet service provider (ISP) and large enterprise networks where many of the distribution routers have more than 200 interfaces.

OSPF for IPv6 routing information is neither sent nor received through the specified router interface. The specified interface address appears as a stub network in the OSPF for IPv6 domain.

For the Intermediate System-to-Intermediate System (IS-IS) protocol, this command instructs IS-IS to advertise the IP addresses for the specified interface without actually running IS-IS on that interface. The no form of this command for IS-IS disables advertising IP addresses for the specified address.

To configure parameters related to Operation, Administration, and Maintenance (OAM) management for an ATM permanent virtual circuit (PVC), switched virtual circuit (SVC), VC class, or VC bundle, or label-controlled ATM (LC-ATM) VC, use the oam retry command in the appropriate command mode. To remove OAM management parameters, use the no form of this command.

Syntax Description

Command Default

ATM PVCs and SVCs

up-count : 3down-count: 5retry-frequency: 1 second

LC-ATM VCs

up-count : 2down-count: 2retry-frequency: 2 seconds

Command Modes

Bundle configuration mode (for a VC bundle)
Control-VC configuration (for an LC-ATM VC)
Interface-ATM-VC configuration (for an ATM PVC or SVC)
PVC range configuration (for an ATM PVC range)
PVC-in-range configuration (for an individual PVC within a PVC range)
VC-class configuration (for a VC class)

Command History

Usage Guidelines

The following guidelines apply to PVCs, SVCs, and VC classes. They do not apply to LC-ATM VCs.

• For ATM PVCs, SVCs, or VC bundles, if the oam retry command is not explicitly configured, the VC inherits the following default configuration (listed in order of precedence):

  • Configuration of the oam retry command in a VC class assigned to the PVC or SVC itself.
  • Configuration of the oam retry command in a VC class assigned to the PVC’s or SVC’s ATM subinterface.
  • Configuration of the oam retry command in a VC class assigned to the PVC’s or SVC’s ATM main interface.
  • Global default: up-count = 3, down-count = 5, retry-frequency = 1 second. This set of defaults assumes that OAM management is enabled using the oam-pvc or oam-svc command. The up-count and retry-frequency arguments do not apply to SVCs.
• To use this command in bundle configuration mode, enter the bundle command to create the bundle or to specify an existing bundle before you enter this command.
• If you use the oam retry command to configure a VC bundle, you configure all VC members of that bundle. VCs in a VC bundle are further subject to the following inheritance rules (listed in order of precedence):

  • VC configuration in bundle-vc mode
  • Bundle configuration in bundle mode (with the effect of assigned VC-class configuration)
  • Subinterface configuration in subinterface mode

Related Commands

To enable Operation, Administration, and Maintenance (OAM) cell emulation on ATM adaptation layer 5 (AAL5) over Multiprotocol Label Switching (MPLS) or Layer 2 Tunnel Protocol Version 3 (L2TPv3), use the oam-ac emulation-enable command in the appropriate configuration mode on both provider edge (PE) routers. To disable OAM cell emulation, use the no form of this command on both routers.

Syntax Description

Command Default

OAM cell emulation is disabled.

Command Modes

L2transport PVC configuration--for an ATM PVC
VC class configuration mode--for a VC class

Command History

Usage Guidelines

This command is used with AAL5 over MPLS or L2TPv3 and is not supported with ATM cell relay over MPLS or L2TPv3.

Related Commands

To enable end-to-end F5 Operation, Administration, and Maintenance (OAM) loopback cell generation and OAM management for an ATM permanent virtual circuit (PVC), virtual circuit (VC) class, or label-controlled ATM (LC-ATM) VC, use the oam-pvc command in the appropriate command mode. To disable generation of OAM loopback cells and OAM management, use the no form of this command.

Syntax Description

Command Default

OAM management and loop detection are disabled.

Command Modes

ATM VC class configuration (config-vc-class)
ATM VC configuration (config-if-atm-vc)
Control-VC configuration (cfg-mpls-atm-cvc)
PVC-in-range configuration (cfg-if-atm-range-pvc)

Command History

Usage Guidelines

If OAM management is enabled, further control of OAM management is configured by using the oam retry command.

ATM VC or VC Classes

If the oam-pvc command is not explicitly configured on an ATM PVC, the PVC inherits the following default configuration (in order of precedence):

• Configuration from the oam-pvc command in a VC class assigned to the PVC itself.
• Configuration from the oam-pvc command in a VC class assigned to the ATM subinterface of the PVC.
• Configuration from the oam-pvccommand in a VC class assigned to the ATM main interface of the PVC.
• Global default: End-to-end F5 OAM loopback cell generation and OAM management are disabled, but if OAM cells are received, they are looped back. The default value for the frequency argument is 10 seconds.

Specifying the ATM VC or VC Classes

You can select the VCs or VC classes to which to apply OAM management and loop detection by using the oam-pvc command in any of the following command modes:

• ATM VC class configuration--for a VC class
• ATM VC configuration mode--for an ATM PVC or loopback mode detection
• Control-VC configuration mode--for enabling OAM management on an LC-ATM VC
• PVC-in-range configuration--for an individual PVC within a PVC range

Loopback Mode Detection

When a PVC traverses an ATM cloud and OAM is enabled, the router sends a loopback cell to the other end and waits for a response to determine whether the circuit is up. However, if an intervening router within the ATM cloud is in loopback mode, the router considers the circuit to be up, when in fact the other end is not reachable.

When enabled, the Loopback Mode Detection Through OAM feature detects when an intervening router is in loopback mode, in which case it sets the OAM state to NOT_VERIFIED. This prevents traffic from being routed on the PVC for as long as any intervening router is detected as being in loopback mode.

Related Commands

To configure the refresh interval for Protection State Coordination (PSC) Protocol messages, use the psc refresh interval command in MPLS TP global configuration mode. To remove the configuration, use the no form of this command.

Syntax Description

Command Default

No intervals are specified.

Command Modes

MPLS TP global configuration mode (config-mpls-tp)

Related Commands

To check Multiprotocol Label Switching (MPLS) label switched path (LSP) connectivity, use the ping mpls command in privileged EXEC mode.

Syntax Description