- Cisco BGP Overview
- BGP 4
- Configuring a Basic BGP Network
- BGP 4 Soft Configuration
- BGP Support for 4-byte ASN
- Connecting to a Service Provider Using External BGP
- BGP Prefix-Based Outbound Route Filtering
- 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 Support for BFD
- IPv6 Routing: Multiprotocol BGP Extensions for IPv6
- IPv6 Multicast Address Family Support for Multiprotocol BGP
- IPv6 Routing: Multiprotocol BGP Link-Local Address Peering
- IPv6 NSF and Graceful Restart for MP-BGP IPv6 Address Family
- BGP NSF Awareness
- BGP Graceful Restart per Neighbor
- Configuring Multiprotocol BGP (MP-BGP) Support for CLNS
- BGP Link Bandwidth
- 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
- Regex Engine Performance Enhancement
- 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
- BGP Next Hop Unchanged
- Per-VRF Assignment of BGP Router ID
- BGP Event-Based VPN Import
- BGP Support for the L2VPN Address Family
- Detecting and Mitigating a BGP Slow Peer
- Configuring BGP: RT Constrained Route Distribution
- Configuring BGP Consistency Checker
- BGP—Origin AS Validation
- BGP Support for NSR with SSO
- BGP NSR Auto Sense
- BGP NSR Support for iBGP Peers
- BGP Graceful Shutdown
- BGP — mVPN BGP sAFI 129 - IPv4
- BGP-MVPN SAFI 129 IPv6
- BGP Attribute Filter and Enhanced Attribute Error Handling
- BGP Additional Paths
- BGP-RT and VPN Distinguisher Attribute Rewrite Wildcard
- BGP—Selective Route Download
- BFD—BGP Multihop Client Support, cBit (IPv4 and IPv6), and Strict Mode
- BGP MIB Support
- BGP 4 MIB Support for per-Peer Received Routes
- BGP PIC Edge for IP and MPLS-VPN
- BGP IPv6 PIC Edge and Core for IP/MPLS
- BGP Unified MPLS iBGP Client
- Cisco-BGP-MIBv2
- BGP Diverse Path Using a Diverse-Path Route Reflector
- BGP-VRF-Aware Conditional Advertisement
- BGP—Support for iBGP Local-AS
- IOS-XE IBGP local-as dual-as
- VPLS BGP Signaling
- BGP NSR Support for MPLS VPNv4 and VPNv6 Inter-AS Option B
- L3VPN iBGP PE-CE
- eiBGP Multipath for Non-VRF Interfaces (IPv4/IPv6)
- 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 Dynamic Neighbors
BGP dynamic neighbor support allows BGP peering to a group of remote neighbors that are defined by a range of IP addresses. Each range can be configured as a subnet IP address. BGP dynamic neighbors are configured using a range of IP addresses and BGP peer groups.
- Finding Feature Information
- Information About BGP Dynamic Neighbors
- How to Configure BGP Dynamic Neighbors
- Configuration Examples for BGP Dynamic Neighbors
- Additional References
- Feature Information for BGP Dynamic Neighbors
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 at the end of this module.
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.
Information About BGP Dynamic Neighbors
BGP Dynamic Neighbors
Support for the BGP Dynamic Neighbors feature was introduced in Cisco IOS Release 12.2(33)SXH on the Cisco Catalyst 6500 series switches. BGP dynamic neighbor support allows BGP peering to a group of remote neighbors that are defined by a range of IP addresses. Each range can be configured as a subnet IP address. BGP dynamic neighbors are configured using a range of IP addresses and BGP peer groups.
In Cisco IOS XE Denali 16.3 release, support for BGP dynamic neighbors was extended to IPv6 BGP peering with VRF support.
After a subnet range is configured for a BGP peer group and a TCP session is initiated by another router for an IP address in the subnet range, a new BGP neighbor is dynamically created as a member of that group. After the initial configuration of subnet ranges and activation of the peer group (referred to as a listen range group ), dynamic BGP neighbor creation does not require any further CLI configuration on the initial router. Other routers can establish a BGP session with the initial router, but the initial router need not establish a BGP session to other routers if the IP address of the remote peer used for the BGP session is not within the configured range.
To support the BGP Dynamic Neighbors feature, the output for the show ip bgp neighbors, show ip bgp peer-group, and show ip bgp summary commands was updated to display information about dynamic neighbors.
A dynamic BGP neighbor will inherit any configuration for the peer group. In larger BGP networks, implementing BGP dynamic neighbors can reduce the amount and complexity of CLI configuration and save CPU and memory usage. Only IPv4 peering is supported.
How to Configure BGP Dynamic Neighbors
Implementing BGP Dynamic Neighbors Using Subnet Ranges
In Cisco IOS Release 12.2(33)SXH, support for BGP dynamic neighbors was introduced. Perform this task to implement the dynamic creation of BGP neighbors using subnet ranges.
In this task, a BGP peer group is created on Router B in the figure below, a global limit is set on the number of dynamic BGP neighbors, and a subnet range is associated with a peer group. Configuring the subnet range enables the dynamic BGP neighbor process. The peer group is added to the BGP neighbor table of the local router, and an alternate autonomous system number is also configured. The peer group is activated under the IPv4 address family.
The next step is to move to another router—Router E in the figure below—where a BGP session is started and the neighbor router, Router B, is configured as a remote BGP peer. The peering configuration opens a TCP session and triggers Router B to create a dynamic BGP neighbor because the IP address that starts the TCP session (192.168.3.2) is within the configured subnet range for dynamic BGP peers. The task moves back to the first router, Router B, to run three show commands that have been modified to display dynamic BGP peer information.
This task requires Cisco IOS Release 12.2(33)SXH, or a later release, to be running.
Note | This task supports only IPv4 BGP peering. |
1.
enable
2.
configure
terminal
3.
router
bgp
autonomous-system-number
4.
bgp
log-neighbor-changes
5.
neighbor
peer-group-name
peer-group
6.
bgp
listen
[limit
max-number]
7.
bgp
listen
[limit
max-number |
range
network
/
length
peer-group
peer-group-name]
8.
neighbor
{ip-address
|
ipv6-address
|
peer-group-name}
ebgp-multihop
[ttl]
9.
neighbor
peer-group-name
remote-as
autonomous-system-number
[alternate-as
autonomous-system-number...]
10.
address-family
ipv4
[mdt |
multicast |
unicast [vrf
vrf-name]]
11.
neighbor
{ip-address |
peer-group-name}
activate
12.
end
13. Move to another router that has an interface within the subnet range for the BGP peer group configured in this task.
14.
enable
15.
configure
terminal
16.
router
bgp
autonomous-system-number
17.
neighbor
{ip-address|
peer-group-name}
remote-as
autonomous-system-number [alternate-as
autonomous-system-number...]
18. Return to the first router.
19.
show
ip
bgp
summary
20.
show
ip
bgp
peer-group
[peer-group-name] [summary]
21.
show
ip
bgp
neighbors
[ip-address]
DETAILED STEPS
Examples
The following output examples were taken from Router B in the figure above after the appropriate configuration steps in this task were completed on both Router B and Router E.
The following output from the show ip bgp summary command shows that the BGP neighbor 192.168.3.2 was dynamically created and is a member of the listen range group, group192. The output also shows that the IP prefix range of 192.168.0.0/16 is defined for the listen range named group192.
Router# show ip bgp 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 *192.168.3.2 4 50000 2 2 0 0 0 00:00:37 0 * Dynamically created based on a listen range command Dynamically created neighbors: 1/(200 max), Subnet ranges: 1 BGP peergroup group192 listen range group members: 192.168.0.0/16
The following output from the show ip bgp peer-group command shows information about the listen range group, group192 that was configured in this task:
Router# show ip bgp peer-group group192 BGP peer-group is group192, remote AS 40000 BGP peergroup group192 listen range group members: 192.168.0.0/16 BGP version 4 Default minimum time between advertisement runs is 30 seconds For address family: IPv4 Unicast BGP neighbor is group192, peer-group external, members: *192.168.3.2 Index 0, Offset 0, Mask 0x0 Update messages formatted 0, replicated 0 Number of NLRIs in the update sent: max 0, min 0
The following sample output from the show ip bgp neighbors command shows that the neighbor 192.168.3.2 is a member of the peer group, group192, and belongs to the subnet range group 192.168.0.0/16, which shows that this peer was dynamically created:
Router# show ip bgp neighbors 192.168.3.2 BGP neighbor is *192.168.3.2, remote AS 50000, external link Member of peer-group group192 for session parameters Belongs to the subnet range group: 192.168.0.0/16 BGP version 4, remote router ID 192.168.3.2 BGP state = Established, up for 00:06:35 Last read 00:00:33, last write 00:00:25, hold time is 180, keepalive intervals Neighbor capabilities: Route refresh: advertised and received(new) Address family IPv4 Unicast: advertised and received Message statistics: InQ depth is 0 OutQ depth is 0 Sent Rcvd Opens: 1 1 Notifications: 0 0 Updates: 0 0 Keepalives: 7 7 Route Refresh: 0 0 Total: 8 8 Default minimum time between advertisement runs is 30 seconds For address family: IPv4 Unicast BGP table version 1, neighbor version 1/0 Output queue size : 0 Index 1, Offset 0, Mask 0x2 1 update-group member group192 peer-group member . . .
Configuring BGP IPv6 Dynamic Neighbor Support with VRF Support
In Cisco IOS XE Denali 16.3 release, support for BGP dynamic neighbors was extended to IPv6 BGP peering.
Note | You can also configure BGP IPv6 dynamic neighbors without VRF support. |
1.
enable
2.
configure
terminal
3.
router
bgp
autonomous-system-number
4.
bgp
listen
[limit
max-number |
range
network
/
length
peer-group
peer-group-name]
5.
address-family [ipv4
|
ipv6] [mdt |
multicast |
unicast [vrf
vrf-name]]
6.
bgp
listen
[limit
max-number]
7.
neighbor
peer-group-name
peer-group
8.
neighbor
peer-group-name
remote-as
autonomous-system-number
[alternate-as
autonomous-system-number...]
9.
address-family [ipv4
|
ipv6] [mdt |
multicast |
unicast [vrf
vrf-name]]
10.
neighbor
{ip-address |
peer-group-name}
activate
11.
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 |
router
bgp
autonomous-system-number
Example: Device(config)# router bgp 45000 |
Enters router configuration mode for the specified routing process. | ||
Step 4 |
bgp
listen
[limit
max-number |
range
network
/
length
peer-group
peer-group-name]
Example: Device(config-router)# bgp listen range 2001::0/64 peer-group group192 |
Associates a subnet range with a BGP peer group and activates the BGP dynamic neighbors feature.
| ||
Step 5 |
address-family [ipv4
|
ipv6] [mdt |
multicast |
unicast [vrf
vrf-name]]
Example: Device(config-router-af)# address-family ipv6 unicast vrf vrf1 |
Enters address family configuration mode to configure BGP peers to accept address-family-specific configurations. | ||
Step 6 |
bgp
listen
[limit
max-number]
Example: Device(config-router)# bgp listen limit 500 |
Specifies the maximum number of prefixes in VRF address family. | ||
Step 7 |
neighbor
peer-group-name
peer-group
Example: Device(config-router)# neighbor group192 peer-group |
Creates a BGP peer group. | ||
Step 8 |
neighbor
peer-group-name
remote-as
autonomous-system-number
[alternate-as
autonomous-system-number...]
Example: Device(config-router)# neighbor group192 remote-as 101 alternate-as 102 |
Adds the IP address or peer group name of the neighbor in the specified autonomous system to the IPv6 BGP neighbor table.
| ||
Step 9 |
address-family [ipv4
|
ipv6] [mdt |
multicast |
unicast [vrf
vrf-name]]
Example: Device(config-router-af)# address-family ipv4 unicast vrf vrf1 |
Enable IPv4 address family for this peer-group. | ||
Step 10 |
neighbor
{ip-address |
peer-group-name}
activate
Example: Device(config-router-af)# neighbor group192 activate |
Activates the neighbor or listen range peer group for the configured address family. | ||
Step 11 | end
Example: Device(config-router-af)# end |
Exits address family configuration mode and returns to privileged EXEC mode. |
Verifying BGP IPv6 Dynamic Neighbor Configuration
Use the show bgp ipv6 unicast summary command to verify the BGP IPv6 unicast address family configuration in global routing table:
Device# show bgp ipv6 unicast 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 *2001::1 4 50000 2 2 0 0 0 00:00:37 0 * Dynamically created based on a listen range command Dynamically created neighbors: 1/(200 max), Subnet ranges: 1 BGP peergroup group192 listen range group members: 2001::0/64
Use the show bgp { ipv4 | ipv6 } unicast peer-group< name> command to verify the IPv6 dynamic neighbors configuration in global routing table:
Device# show bgp ipv6 unicast peer-group group192 BGP peer-group is group192, remote AS 40000 BGP peergroup group192 listen range group members: 2001::0/64 BGP version 4 Default minimum time between advertisement runs is 30 seconds For address family: IPv6 Unicast BGP neighbor is group192, peer-group external, members: *2001::1 Index 0, Offset 0, Mask 0x0 Update messages formatted 0, replicated 0 Number of NLRIs in the update sent: max 0, min 0
You can use the following commands to verify the BGP IPv6 dynamic neighbors configuration in the VRF routing table:
Configuration Examples for BGP Dynamic Neighbors
Example: Implementing BGP Dynamic Neighbors Using Subnet Ranges
In the following example, two BGP peer groups are created on Router B in the figure below, a global limit is set on the number of dynamic BGP neighbors, and a subnet range is associated with a peer group. Configuring the subnet range enables the dynamic BGP neighbor process. The peer groups are added to the BGP neighbor table of the local router, and an alternate autonomous system number is also configured for one of the peer groups, group192. The subnet range peer groups and a standard BGP peer are then activated under the IPv4 address family.
The configuration moves to another router—Router A in the figure below—where a BGP session is started and the neighbor router, Router B, is configured as a remote BGP peer. The peering configuration opens a TCP session and triggers Router B to create a dynamic BGP neighbor because the IP address that starts the TCP session (192.168.1.2) is within the configured subnet range for dynamic BGP peers.
A third router—Router E in the figure below—also starts a BGP peering session with Router B. Router E is in the autonomous system 50000, which is the configured alternate autonomous system. Router B responds to the resulting TCP session by creating another dynamic BGP peer.
This example concludes with the output of the show ip bgp summary command entered on Router B.
Router B
enable configure terminal router bgp 45000 bgp log-neighbor-changes bgp listen limit 200 bgp listen range 172.21.0.0/16 peer-group group172 bgp listen range 192.168.0.0/16 peer-group group192 neighbor group172 peer-group neighbor group172 remote-as 45000 neighbor group192 peer-group neighbor group192 remote-as 40000 alternate-as 50000 neighbor 172.16.1.2 remote-as 45000 address-family ipv4 unicast neighbor group172 activate neighbor group192 activate neighbor 172.16.1.2 activate end
Router A
enable configure terminal router bgp 40000 neighbor 192.168.1.1 remote-as 45000 exit
Router E
enable configure terminal router bgp 50000 neighbor 192.168.3.1 remote-as 45000 exit
After both Router A and Router E are configured, the show ip bgp summary command is run on Router B. The output displays the regular BGP neighbor, 172.16.1.2, and the two BGP neighbors that were created dynamically when Router A and Router E initiated TCP sessions for BGP peering to Router B. The output also shows information about the configured listen range subnet groups.
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 15 15 1 0 0 00:12:20 0 *192.168.1.2 4 40000 3 3 1 0 0 00:00:37 0 *192.168.3.2 4 50000 6 6 1 0 0 00:04:36 0 * Dynamically created based on a listen range command Dynamically created neighbors: 2/(200 max), Subnet ranges: 2 BGP peergroup group172 listen range group members: 172.21.0.0/16 BGP peergroup group192 listen range group members: 192.168.0.0/16
Example: Configuring BGP IPv6 Dynamic Neighbor Support with VRF Support
Configuring BGP IPv6 Dynamic Neighbor Support with VRF Support
enable configure terminal router bgp 55000 bgp listen range 2001::0/64 peer-group group182 address-family ipv6 unicast vrf vrf2 bgp listen limit 600 neighbor group182 peer-group neighbor group182 remote-as 103 alternate-as 104 address-family ipv4 unicast vrf vrf2 neighbor group182 activate end
Configuring BGP IPv6 Dynamic Neighbor Support without VRF Support
enable configure terminal router bgp 100 bgp listen range 2001::0/64 peer-group group192 bgp listen limit 500 neighbor group192 peer-group neighbor group192 remote-as 101 alternate-as 102 address family ipv6 unicast neighbor group192 activate address family ipv4 unicast neighbor group192 activate end
Additional References
Related Documents
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
BGP commands |
Standards and RFCs
Standard/RFC |
Title |
---|---|
RFC 2918 |
Route Refresh Capability for BGP-4 |
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 Dynamic Neighbors
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 Dynamic Neighbors |
15.0(1)S |
BGP dynamic neighbor support allows BGP peering to a group of remote neighbors that are defined by a range of IP addresses. Each range can be configured as a subnet IP address. BGP dynamic neighbors are configured using a range of IP addresses and BGP peer groups. After a subnet range is configured for a BGP peer group 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 for the peer group. The following commands were introduced or modified by this feature: bgp listen, debug ip bgp range, neighbor remote-as, show ip bgp neighbors, show ip bgp peer-group, and show ip bgp summary. |
BGP IPv6 Dynamic Neighbor Support and VRF Support |
Cisco IOS XE Denali 16.3.1 |
In Cisco IOS XE Denali 16.3 release, support for BGP dynamic neighbors was extended to IPv6 BGP peering with support for VRF. The following commands were introduced or modified by this feature: bgp listen, debug ip bgp range, neighbor remote-as, show bgp neighbors, show bgp summary, show bgp vpnv6 unicast vrf neighbors, show bgp vpnv6 unicast vrf peer-group , show bgp vpnv6 unicast vrf summary. |