- Read Me First
- Cisco BGP Overview
- BGP 4
- Configuring a Basic BGP Network
- BGP 4 Soft Configuration
- BGP Support for 4-byte ASN
- IPv6 Routing: Multiprotocol BGP Extensions for IPv6
- IPv6 Routing: Multiprotocol BGP Link-Local Address Peering
- IPv6 Multicast Address Family Support for Multiprotocol BGP
- Configuring Multiprotocol BGP (MP-BGP) Support for CLNS
- BGP IPv6 Admin Distance
- Connecting to a Service Provider Using External BGP
- BGP Route-Map Continue
- BGP Route-Map Continue Support for Outbound Policy
- Removing Private AS Numbers from the AS Path in BGP
- Configuring BGP Neighbor Session Options
- BGP Neighbor Policy
- BGP Dynamic Neighbors
- BGP Support for Next-Hop Address Tracking
- BGP Restart Neighbor Session After Max-Prefix Limit Reached
- BGP Support for Dual AS Configuration for Network AS Migrations
- Configuring Internal BGP Features
- BGP VPLS Auto Discovery Support on Route Reflector
- BGP FlowSpec Route-reflector Support
- BGP Flow Specification Client
- BGP NSF Awareness
- BGP Graceful Restart per Neighbor
- BGP Support for BFD
- IPv6 NSF and Graceful Restart for MP-BGP IPv6 Address Family
- BGP Persistence
- BGP Link Bandwidth
- Border Gateway Protocol Link-State
- iBGP Multipath Load Sharing
- BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN
- Loadsharing IP Packets over More Than Six Parallel Paths
- BGP Policy Accounting
- BGP Policy Accounting Output Interface Accounting
- BGP Cost Community
- BGP Support for IP Prefix Import from Global Table into a VRF Table
- BGP Support for IP Prefix Export from a VRF Table into the Global Table
- BGP per Neighbor SoO Configuration
- Per-VRF Assignment of BGP Router ID
- BGP Next Hop Unchanged
- BGP Support for the L2VPN Address Family
- BGP Event-Based VPN Import
- BGP Best External
- BGP PIC Edge for IP and MPLS-VPN
- Detecting and Mitigating a BGP Slow Peer
- Configuring BGP: RT Constrained Route Distribution
- Configuring a BGP Route Server
- BGP Diverse Path Using a Diverse-Path Route Reflector
- BGP Enhanced Route Refresh
- Configuring BGP Consistency Checker
- BGP—Origin AS Validation
- BGP MIB Support
- BGP 4 MIB Support for Per-Peer Received Routes
- BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO) Using L2VPN VPLS
- BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO) Using L2VPN VPLS
- BGP NSR Auto Sense
- BGP NSR Support for iBGP Peers
- BGP Graceful Shutdown
- BGP — mVPN BGP sAFI 129 - IPv4
- BGP-MVPN SAFI 129 IPv6
- BFD—BGP Multihop Client Support, cBit (IPv4 and IPv6), and Strict Mode
- BGP Attribute Filter and Enhanced Attribute Error Handling
- BGP Additional Paths
- BGP-Multiple Cluster IDs
- BGP-VPN Distinguisher Attribute
- BGP-RT and VPN Distinguisher Attribute Rewrite Wildcard
- VPLS BGP Signaling
- Multicast VPN BGP Dampening
- BGP—IPv6 NSR
- BGP-VRF-Aware Conditional Advertisement
- BGP—Selective Route Download
- BGP—Support for iBGP Local-AS
- eiBGP Multipath for Non-VRF Interfaces (IPv4/IPv6)
- L3VPN iBGP PE-CE
- BGP NSR Support for MPLS VPNv4 and VPNv6 Inter-AS Option B
- BGP-RTC for Legacy PE
- BGP PBB EVPN Route Reflector Support
- BGP Monitoring Protocol
- VRF Aware BGP Translate-Update
- BGP Support for MTR
- BGP Accumulated IGP
- BGP MVPN Source-AS Extended Community Filtering
- BGP AS-Override Split-Horizon
- BGP Support for Multiple Sourced Paths Per Redistributed Route
- Maintenance Function: BGP Routing Protocol
BGP Support for MTR
The BGP Support for MTR feature provides Border Gateway Protocol (BGP) support for multiple logical topologies over a single physical network. This module describes how to configure BGP for Multitopology Routing (MTR).
- Finding Feature Information
- Prerequisites for BGP Support for MTR
- Restrictions for BGP Support for MTR
- Information About BGP Support for MTR
- How to Configure BGP Support for MTR
- Configuration Examples for BGP Support for MTR
- Additional References
- Feature Information for BGP Support for MTR
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for BGP Support for MTR
Restrictions for BGP Support for MTR
Redistribution within a topology is permitted. Redistribution from one topology to another is not permitted. This restriction is designed to prevent routing loops. You can use topology translation or topology import functionality to move routes from one topology to another.
Only a single multicast topology can be configured, and only the base topology can be specified if a multicast topology is created.
Information About BGP Support for MTR
Routing Protocol Support for MTR
You must enable IP routing on the device for Multitopology Routing (MTR) to operate. MTR supports static and dynamic routing in Cisco software. You can enable dynamic routing per topology to support interdomain and intradomain routing. Route calculation and forwarding are independent for each topology. MTR support is integrated into Cisco software for the following protocols:
Border Gateway Protocol (BGP)
Enhanced Interior Gateway Routing Protocol (EIGRP)
Integrated Intermediate System-to-Intermediate System (IS-IS)
Open Shortest Path First (OSPF)
You apply the per-topology configuration in router address family configuration mode of the global routing process (router configuration mode). The address family and subaddress family are specified when the device enters address family configuration mode. You specify the topology name and topology ID by entering the topology command in address family configuration mode.
You configure each topology with a unique topology ID under the routing protocol. The topology ID is used to identify and group Network Layer Reachability Information (NLRI) for each topology in updates for a given protocol. In OSPF, EIGRP, and IS-IS, you enter the topology ID during the first configuration of the topology command for a class-specific topology. In BGP, you configure the topology ID by entering the bgp tid command under the topology configuration.
You can configure class-specific topologies with different metrics than the base topology. Interface metrics configured on the base topology can be inherited by the class-specific topology. Inheritance occurs if no explicit inheritance metric is configured in the class-specific topology.
You configure BGP support only in router configuration mode. You configure Interior Gateway Protocol (IGP) support in router configuration mode and in interface configuration mode.
By default, interfaces are not included in nonbase topologies. For routing protocol support for EIGRP, IS-IS, and OSPF, you must explicitly configure a nonbase topology on an interface. You can override the default behavior by using the all-interfaces command in address family topology configuration mode. The all-interfaces command causes the nonbase topology to be configured on all interfaces of the device that are part of the default address space or the virtual routing and forwarding (VRF) instance in which the topology is configured.
BGP Network Scope
To implement Border Gateway Protocol (BGP) support for Multitopology Routing (MTR), the scope hierarchy is required, but the scope hierarchy is not limited to MTR use. The scope hierarchy introduces new configuration modes such as router scope configuration mode. The device enters router scope configuration mode when you configure the scope command in router configuration mode. When this command is entered, a collection of routing tables is created.
You configure BGP commands under the scope hierarchy for a single network (globally), or on a per-virtual routing and forwarding (VRF) basis; these configurations are referred to as scoped commands. The scope hierarchy can contain one or more address families.
MTR CLI Hierarchy Under BGP
The Border Gateway Protocol (BGP) CLI provides backward compatibility for pre-Multitopology Routing (MTR) BGP configuration and provides a hierarchical implementation of MTR. Router configuration mode is backward 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, you configure general session commands and peer templates to be used in address family configuration mode or in topology configuration mode.
After configuring any global commands, you define the scope either globally or for a specific virtual routing and forwarding (VRF) instance. The device enters address family configuration mode when you configure the address-family command in router scope configuration mode or in router configuration mode. Unicast is the default address family if no subaddress family identifier (SAFI) is specified. MTR supports only the IPv4 address family with a SAFI of unicast or multicast.
When the device enters address family configuration mode from router configuration mode, the software configures BGP to use pre-MTR-based CLI. This configuration mode is backward compatible with pre-existing address family configurations. Entering address family configuration mode from router scope configuration mode configures the device 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.
The device enters BGP topology configuration mode when you configure the topology command in address family configuration mode. You can configure up to 32 topologies (including the base topology) on a device. You configure the topology ID by entering the bgp tid command. All address family and subaddress family configuration parameters for the topology are configured here.
Note | Configuring a scope for a BGP routing process removes CLI support for pre-MTR-based configuration. |
The following example shows the hierarchy levels that are used when you configure BGP for MTR implementation:
router bgp <autonomous-system-number> ! Global commands scope {global | vrf <vrf-name>} ! Scoped commands address-family {<afi>} [<safi>] ! Address family specific commands topology {<topology-name> | base} ! topology specific commands
BGP Sessions for Class-Specific Topologies
Multitopology Routing (MTR) is configured under the Border Gateway Protocol (BGP) on a per-session basis. The base unicast and multicast topologies are carried in the global (default) session. A separate session is created for each class-specific topology that is configured under a BGP routing process. Each session is identified by its topology ID. BGP performs a best-path calculation individually for each class-specific topology. A separate Routing Information Base (RIB) and Forwarding Information Base (FIB) are maintained for each session.
Topology Translation Using BGP
Depending on the design and policy requirements for your network, you might need to install routes from a class-specific topology on one device in a class-specific topology on a neighboring device. Topology translation functionality using the Border Gateway Protocol (BGP) provides support for this operation. Topology translation is BGP neighbor-session based. You configure the neighbor translate-topology command by using the IP address and topology ID from the neighbor.
The topology ID identifies the class-specific topology of the neighbor. The routes in the class-specific topology of the neighbor are installed in the local class-specific Routing Information Base (RIB). BGP performs a best-path calculation on all installed routes and installs these routes into the local class-specific RIB. If a duplicate route is translated, BGP selects and installs only one instance of the route per standard BGP best-path calculation behavior.
Topology Import Using BGP
Importing topologies using the Border Gateway Protocol (BGP) is similar to topology translation. The difference is that routes are moved between class-specific topologies on the same device. You configure this function by entering the import topology command and specify the name of the class-specific topology or base topology. Best-path calculations are run on the imported routes before they are installed into the topology Routing Information Base (RIB). This import topology command also includes a route-map keyword to allow you to filter routes that are moved between class-specific topologies.
How to Configure BGP Support for MTR
Activating an MTR Topology by Using BGP
Perform this task to activate a Multitopology Routing (MTR) topology inside an address family by using the Border Gateway Protocol (BGP). This task is configured on Device B in the figure below and must also be configured on Device D and Device E. In this task, a scope hierarchy is configured to apply globally, and a neighbor is configured in router scope configuration mode. Under the IPv4 unicast address family, an MTR topology that applies to video traffic is activated for the specified neighbor. There is no interface configuration mode for BGP topologies.
1.
enable
2.
configure terminal
3.
router bgp
autonomous-system-number
4.
scope {global |
vrf
vrf-name}
5.
neighbor {ip-address |
peer-group-name}
remote-as
autonomous-system-number
6.
neighbor {ip-address |
peer-group-name}
transport {connection-mode {active |
passive} |
path-mtu-discovery |
multi-session |
single-session}
7.
address-family ipv4 [mdt |
multicast |
unicast]
8.
topology {base |
topology-name}
9.
bgp tid
number
10.
neighbor
ip-address
activate
11.
neighbor {ip-address |
peer-group-name}
translate-topology
number
12.
end
13.
clear ip bgp topology
{* |
topology-name} {as-number |
dampening [network-address [network-mask]] |
flap-statistics [network-address [network-mask]] |
peer-group
peer-group-name |
table-map |
update-group [number |
ip-address]} [in [prefix-filter] |
out |
soft [in [prefix-filter] |
out]]
14.
show ip bgp topology {* |
topology}
summary
DETAILED STEPS
What to Do Next
Repeat this task for every topology that you want to enable, and repeat this configuration on all neighbor devices that are to use the topologies.
If you want to import routes from one Multitopology Routing (MTR) topology to another on the same device, see the “Importing Routes from an MTR Topology by Using BGP” section.
Importing Routes from an MTR Topology by Using BGP
Perform this task to import routes from one Multitopology Routing (MTR) topology to another on the same device, when multiple topologies are configured on the same device. In this task, a prefix list is defined to permit prefixes from the 10.2.2.0 network, and this prefix list is used with a route map to filter routes moved from the imported topology. A global scope is configured, address family IPv4 is entered, the VIDEO topology is specified, the VOICE topology is imported, and the routes are filtered using the route map named 10NET.
1.
enable
2.
configure terminal
3.
ip prefix-list
list-name [seq
number] {deny |
permit}
network/length [ge
ge-length] [le
le-length]
4.
route-map
map-name [permit |
deny] [sequence-number]
5.
match ip address {access-list-number [access-list-number ... |
access-list-name...] |
access-list-name [access-list-number ... |
access-list-name] |
prefix-list
prefix-list-name [prefix-list-name...]}
6.
exit
7.
router bgp
autonomous-system-number
8.
scope {global |
vrf
vrf-name}
9.
address-family ipv4 [mdt |
multicast |
unicast]
10.
topology {base |
topology-name}
11.
import topology {base |
topology-name} [route-map
map-name]
12.
end
DETAILED STEPS
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable
Example: Device> enable |
Enables privileged EXEC mode. |
Step 2 |
configure terminal
Example: Device# configure terminal |
Enters global configuration mode. |
Step 3 |
ip prefix-list
list-name [seq
number] {deny |
permit}
network/length [ge
ge-length] [le
le-length]
Example: Device(config)# ip prefix-list TEN permit 10.2.2.0/24 |
Configures an IP prefix list. |
Step 4 |
route-map
map-name [permit |
deny] [sequence-number]
Example: Device(config)# route-map 10NET |
Creates a route map and enters route-map configuration mode. |
Step 5 |
match ip address {access-list-number [access-list-number ... |
access-list-name...] |
access-list-name [access-list-number ... |
access-list-name] |
prefix-list
prefix-list-name [prefix-list-name...]}
Example: Device(config-route-map)# match ip address prefix-list TEN |
Configures the route map to match a prefix that is permitted by a standard access list, an extended access list, or a prefix list. |
Step 6 |
exit
Example: Device(config-route-map)# exit |
Exits route-map configuration mode and returns to global configuration mode. |
Step 7 |
router bgp
autonomous-system-number
Example: Device(config)# router bgp 50000 |
Enters router configuration mode to create or configure a Border Gateway Protocol (BGP) routing process. |
Step 8 |
scope {global |
vrf
vrf-name}
Example: Device(config-router)# scope global |
Defines the scope to the BGP routing process and enters router scope configuration mode.
|
Step 9 |
address-family ipv4 [mdt |
multicast |
unicast]
Example: Device(config-router-scope)# address-family ipv4 |
Enters router scope address family configuration mode to configure an address family session under BGP. |
Step 10 |
topology {base |
topology-name}
Example: Device(config-router-scope-af)# topology VIDEO |
Configures the topology instance in which BGP routes class-specific or base topology traffic, and enters router scope address family topology configuration mode. |
Step 11 |
import topology {base |
topology-name} [route-map
map-name]
Example: Device(config-router-scope-af-topo)# import topology VOICE route-map 10NET |
(Optional) Configures BGP to move routes from one topology to another on the same device. |
Step 12 |
end
Example: Device(config-router-scope-af-topo)# end |
(Optional) Exits router scope address family topology configuration mode and returns to privileged EXEC mode. |
Configuration Examples for BGP Support for MTR
Example: BGP Topology Translation Configuration
The following example shows how to configure the Border Gateway Protocol (BGP) in the VIDEO topology and how to configure topology translation with the 192.168.2.2 neighbor:
router bgp 45000 scope global neighbor 172.16.1.1 remote-as 50000 neighbor 192.168.2.2 remote-as 55000 neighbor 172.16.1.1 transport multi-session neighbor 192.168.2.2 transport multi-session address-family ipv4 topology VIDEO bgp tid 100 neighbor 172.16.1.1 activate neighbor 192.168.2.2 activate neighbor 192.168.2.2 translate-topology 200 end clear ip bgp topology VIDEO 50000
Example: BGP Global Scope and VRF Configuration
The following example shows how to configure a global scope for a unicast topology and also for a multicast topology. After the device exits the router scope configuration mode, a scope is configured for the virtual routing and forwarding (VRF) instance named DATA.
router bgp 45000 scope global bgp default ipv4-unicast neighbor 172.16.1.2 remote-as 45000 neighbor 192.168.3.2 remote-as 50000 address-family ipv4 unicast topology VOICE bgp tid 100 neighbor 172.16.1.2 activate exit address-family ipv4 multicast topology base neighbor 192.168.3.2 activate exit exit exit scope vrf DATA neighbor 192.168.1.2 remote-as 40000 address-family ipv4 neighbor 192.168.1.2 activate end
Examples: BGP Topology Verification
The following example shows summary output for the show ip bgp topology command. Information is displayed about Border Gateway Protocol (BGP) neighbors configured to use the Multitopology Routing (MTR) topology named VIDEO.
Device# show ip bgp topology VIDEO summary BGP router identifier 192.168.3.1, local AS number 45000 BGP table version is 1, main routing table version 1 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 172.16.1.2 4 45000 289 289 1 0 0 04:48:44 0 192.168.3.2 4 50000 3 3 1 0 0 00:00:27 0
The following partial output displays BGP neighbor information under the VIDEO topology:
Device# show ip bgp topology VIDEO neighbors 172.16.1.2 BGP neighbor is 172.16.1.2, remote AS 45000, internal link BGP version 4, remote router ID 192.168.2.1 BGP state = Established, up for 04:56:30 Last read 00:00:23, last write 00:00:21, hold time is 180, keepalive interval is 60 seconds Neighbor sessions: 1 active, is multisession capable Neighbor capabilities: Route refresh: advertised and received(new) Message statistics, state Established: InQ depth is 0 OutQ depth is 0 Sent Rcvd Opens: 1 1 Notifications: 0 0 Updates: 0 0 Keepalives: 296 296 Route Refresh: 0 0 Total: 297 297 Default minimum time between advertisement runs is 0 seconds For address family: IPv4 Unicast topology VIDEO Session: 172.16.1.2 session 1 BGP table version 1, neighbor version 1/0 Output queue size : 0 Index 1, Offset 0, Mask 0x2 1 update-group member Topology identifier: 100 . . . Address tracking is enabled, the RIB does have a route to 172.16.1.2 Address tracking requires at least a /24 route to the peer Connections established 1; dropped 0 Last reset never Transport(tcp) path-mtu-discovery is enabled Connection state is ESTAB, I/O status: 1, unread input bytes: 0 Minimum incoming TTL 0, Outgoing TTL 255 Local host: 172.16.1.1, Local port: 11113 Foreign host: 172.16.1.2, Foreign port: 179 . . .
Example: Importing Routes from an MTR Topology by Using BGP
The following example shows how to configure an access list to be used by a route map named VOICE to filter routes imported from the Multitopology Routing (MTR) topology named VOICE. Only routes with the prefix 192.168.1.0 are imported.
access-list 1 permit 192.168.1.0 0.0.0.255 route-map BLUE match ip address 1 exit router bgp 50000 scope global neighbor 10.1.1.2 remote-as 50000 neighbor 172.16.1.1 remote-as 60000 address-family ipv4 topology VIDEO bgp tid 100 neighbor 10.1.1.2 activate neighbor 172.16.1.1 activate import topology VOICE route-map VOICE end clear ip bgp topology VIDEO 50000
Additional References
Related Documents
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
Multitopology Routing (MTR) commands |
|
Border Gateway Protocol (BGP) commands |
|
BGP concepts and tasks |
IP Routing: BGP Configuration Guide |
Technical Assistance
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for BGP Support for MTR
The following table provides release information about the feature or features described in this module. This table 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.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
---|---|---|
BGP Support for MTR |
12.2(33)SRB 15.0(1)S |
This feature provides Border Gateway Protocol (BGP) support for multiple logical topologies over a single physical network. In Cisco IOS XE Release 2.5, support was added for the Cisco ASR 1000 Series Routers. The following commands were introduced or modified: address-family ipv4, bgp tid, clear ip bgp topology, import topology, neighbor translate-topology, neighbor transport, scope, show ip bgp topology, topology. |