Cisco Cisco IOS Software Release 12.2(33)SRE
Multi-Topology Routing
Information About Multi-Topology Routing
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Cisco IOS Release 12.2(33)SRB
configuration mode. The all-interfaces command causes the non-base topology to be configured on all
interfaces of the router that are part of the default address space or the VRF in which the topology is
configured.
interfaces of the router that are part of the default address space or the VRF in which the topology is
configured.
BGP Routing Protocol Support for MTR
Before using BGP to support MTR, you should be familiar with the following concepts:
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BGP Network Scope
A new configuration hierarchy, named scope, has been introduced into the BGP protocol. To implement
MTR for BGP, the scope hierarchy is required, but the scope hierarchy is not limited to MTR use. The
scope hierarchy introduces some new configuration modes such as router scope configuration mode.
Router scope configuration mode is entered by configuring the scope command in router configuration
mode, and a collection of routing tables is created when this command is entered. BGP commands
configured under the scope hierarchy are configured for a single network (globally), or on a per-VRF
basis, and are referred to as scoped commands. The scope hierarchy can contain one or more address
families.
MTR for BGP, the scope hierarchy is required, but the scope hierarchy is not limited to MTR use. The
scope hierarchy introduces some new configuration modes such as router scope configuration mode.
Router scope configuration mode is entered by configuring the scope command in router configuration
mode, and a collection of routing tables is created when this command is entered. BGP commands
configured under the scope hierarchy are configured for a single network (globally), or on a per-VRF
basis, and are referred to as scoped commands. The scope hierarchy can contain one or more address
families.
MTR CLI Hierarchy Under BGP
The BGP CLI has been modified to provide backwards compatibility for pre-MTR BGP configuration
and to provide a hierarchical implementation of MTR. Router configuration mode is backwards
compatible with the pre-address family and pre-MTR configuration CLI. Global commands that affect
all networks are configured in this configuration mode. For address-family and topology configuration,
general session commands and peer templates can be configured to be used in the address-family or
topology configuration modes.
and to provide a hierarchical implementation of MTR. Router configuration mode is backwards
compatible with the pre-address family and pre-MTR configuration CLI. Global commands that affect
all networks are configured in this configuration mode. For address-family and topology configuration,
general session commands and peer templates can be configured to be used in the address-family or
topology configuration modes.
After any global commands are configured, the scope is defined either globally or for a specific VRF.
Address family configuration mode is entered by configuring the address-family command in router
scope configuration mode or router configuration mode. Unicast is the default address family if no
subaddress family (SAFI) is specified. MTR supports only the IPv4 address family with a SAFI of
unicast or multicast. Entering address family configuration mode from router configuration mode
configures BGP to use pre-MTR-based CLI. This configuration mode is backwards compatible with
pre-existing address family configurations. Entering address family configuration mode from router
scope configuration mode configures the router to use the hierarchical CLI that supports MTR. Address
family configuration parameters that are not specific to a topology are entered in this address family
configuration mode.
Address family configuration mode is entered by configuring the address-family command in router
scope configuration mode or router configuration mode. Unicast is the default address family if no
subaddress family (SAFI) is specified. MTR supports only the IPv4 address family with a SAFI of
unicast or multicast. Entering address family configuration mode from router configuration mode
configures BGP to use pre-MTR-based CLI. This configuration mode is backwards compatible with
pre-existing address family configurations. Entering address family configuration mode from router
scope configuration mode configures the router to use the hierarchical CLI that supports MTR. Address
family configuration parameters that are not specific to a topology are entered in this address family
configuration mode.
BGP topology configuration mode is entered by configuring the topology (BGP) command in address
family configuration mode. Up to 32 topologies (including the base topology) can be configured on a
router. The topology ID is configured by entering the bgp tid command. All address family and
subaddress family configuration parameters for the topology are configured here.
family configuration mode. Up to 32 topologies (including the base topology) can be configured on a
router. The topology ID is configured by entering the bgp tid command. All address family and
subaddress family configuration parameters for the topology are configured here.