Basic BGP Configuration

This section describes how to configure BGP using either BGP numbered or BGP unnumbered. With BGP unnumbered, you can set up BGP peering between your Cumulus Linux switches and exchange IPv4 prefixes without having to configure an IPv4 address on each switch.

BGP unnumbered simplifies configuration. NVIDIA recommends you use BGP unnumbered for data center deployments.

When you enable BGP for the first time, the FRR service restarts, which might impact traffic. Any time you enable or disable BGP, or change the ASN, the FRR service also restarts.

BGP Numbered

To configure BGP numbered on a BGP node, you need to:

Assign an ASN to identify this BGP node. In a two-tier leaf and spine configuration, you can use auto BGP, where Cumulus Linux assigns an ASN automatically.
If necessary, specify a router ID. NVUE automatically assigns the loopback address of the switch to be the router ID. FRR automatically assigns the router ID to be the loopback address or the highest IPv4 address for the interface. If you do not have a loopback address configured or want to use a specific router ID, set the router ID globally or per VRF.
Specify where to distribute routing information by providing the IP address and ASN of the neighbor.
- For BGP numbered, this is the IP address of the interface between the two peers; the interface must be a layer 3 access port.
- The ASN can be a number, or internal for a neighbor in the same AS or external for a neighbor in a different AS.
Specify which prefixes to originate from this BGP node.

NVUE Commands

leaf01

Identify the BGP node by assigning an ASN.
- To assign an ASN manually:
```
cumulus@leaf01:~$ nv set router bgp autonomous-system 65101
```
- To use auto BGP to assign an ASN automatically on the leaf:
```
cumulus@leaf01:~$ nv set router bgp autonomous-system leaf
```
  The auto BGP leaf keyword is only used to configure the ASN. The configuration files and nv show commands display the AS number.
BGP automatically assigns the loopback address of the switch to be the router ID. If you do not have a loopback address configured or you do not want to use the loopback address as the router ID, you must assign the router ID either globally with the nv set router bgp router-id command or in a VRF with the nv set vrf <vrf> router bgp router-id command.
```
cumulus@leaf01:~$ nv set router bgp router-id 10.10.10.1
```
Specify the BGP neighbor to which you want to distribute routing information.
```
cumulus@leaf01:~$ nv set vrf default router bgp neighbor 10.0.1.0 remote-as external
```
For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. Cumulus Linux enables the IPv4 address family by default; you do not need to run the activate command for IPv4 route exchange.
```
cumulus@leaf01:~$ nv set vrf default router bgp neighbor 2001:db8:0002::0a00:0002 remote-as external
cumulus@leaf01:~$ nv set vrf default router bgp neighbor 2001:db8:0002::0a00:0002 address-family ipv6-unicast enable on
```
For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

Specify which prefixes to originate:

cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.10.10.1/32
cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.1.10.0/24
cumulus@leaf01:~$ nv config apply

IPv6 prefix example:

cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv6-unicast network 2001:db8::1/128
cumulus@leaf01:~$ nv config apply

After you run nv config save, the NVUE Commands create the following configuration snippet in the /etc/nvue.d/startup.yaml file:

cumulus@leaf01:~$ sudo cat /etc/nvue.d/startup.yaml
...
- set:
    router:
      bgp:
        autonomous-system: 65101
        enable: on
        router-id: 10.10.10.1
    vrf:
      default:
        router:
          bgp:
            address-family:
              ipv4-unicast:
                enable: on
                network:
                  10.1.10.0/24: {}
                  10.10.10.1/32: {}
            enable: on
            neighbor:
              10.0.1.0:
                remote-as: external
                type: numbered

spine01

Identify the BGP node by assigning an ASN.
- To assign an ASN manually:
```
cumulus@spine01:~$ nv set router bgp autonomous-system 65199
```
- To use auto BGP to assign an ASN automatically on the spine:
```
cumulus@spine01:~$ nv set router bgp autonomous-system spine
```
  The auto BGP spine keyword is only used to configure the ASN. The configuration files and nv show commands display the AS number.
BGP automatically assigns the loopback address of the switch to be the router ID. If you do not have a loopback address configured or you do not want to use the loopback address as the router ID, you must assign the router ID either globally with the nv set router bgp router-id command or in a VRF with the nv set vrf <vrf> router bgp router-id command.
```
cumulus@spine01:~$ nv set router bgp router-id 10.10.10.101
```
Specify the BGP neighbor to which you want to distribute routing information.
```
cumulus@spine01:~$ nv set vrf default router bgp neighbor 10.0.1.0 remote-as external
```
For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. Cumulus Linux enables the IPv4 address family by default; you do not need to run the activate command for IPv4 route exchange.
```
cumulus@spine01:~$ nv set vrf default router bgp neighbor 2001:db8:0002::0a00:1 remote-as external
cumulus@spine01:~$ nv set vrf default router bgp neighbor address-family ipv6-unicast 2001:db8:0002::0a00:1 enable on
```
For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

Specify which prefixes to originate:

cumulus@spine01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.10.10.101/32
cumulus@spine01:~$ nv config apply

IPv6 prefix example:

cumulus@spine01:~$ nv set vrf default router bgp address-family ipv6-unicast network 2001:db8::101/128
cumulus@spine01:~$ nv config apply

After you run nv config save, the NVUE Commands create the following configuration snippet in the /etc/nvue.d/startup.yaml file:

cumulus@spine01:~$ sudo cat /etc/nvue.d/startup.yaml
...
- set:
    router:
      bgp:
        autonomous-system: 65199
        enable: on
        router-id: 10.10.10.101
    vrf:
      default:
        router:
          bgp:
            address-family:
              ipv4-unicast:
                enable: on
                network:
                  10.10.10.101/32: {}
            enable: on
            neighbor:
              10.0.1.0:
                remote-as: external
                type: numbered

vtysh Commands

leaf01

Enable the bgpd daemon as described in FRRouting.
Identify the BGP node by assigning an ASN and, if necessary, the router ID.

BGP automatically assigns the router ID using the loopback address or the highest IPv4 address for the interface. If you want to assign a specific IPv4 address for the router ID, add the router ID globally or per VRF.
```
cumulus@leaf01:~$ sudo vtysh
...
leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1
```
Specify where to distribute routing information:
```
leaf01(config-router)# neighbor 10.0.1.0 remote-as external
```
For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. Cumulus Linux enables the IPv4 address family by default; you do not need to run the activate command for IPv4 route exchange.
```
leaf01(config-router)# neighbor 2001:db8:0002::0a00:1 remote-as external
leaf01(config-router)# address-family ipv6 unicast
leaf01(config-router-af)# neighbor 2001:db8:0002::0a00:1 activate
```
For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

Specify which prefixes to originate:

leaf01(config-router)# address-family ipv4
leaf01(config-router-af)# network 10.10.10.1/32
leaf01(config-router-af)# network 10.1.10.0/24
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

IPv6 prefix example:

leaf01(config-router)# address-family ipv6
leaf01(config-router-af)# network 2001:db8::1/128
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit

spine01

Enable the bgpd daemon as described in FRRouting.
Identify the BGP node by assigning an ASN and, if necessary, the router ID.

BGP automatically assigns the router ID using the loopback address or the highest IPv4 address for the interface. If you want to assign a specific IPv4 address for the router ID, add the router ID globally or per VRF.
```
cumulus@spine01:~$ sudo vtysh
...
spine01# configure terminal
spine01(config)# router bgp 65199
spine01(config-router)# bgp router-id 10.10.10.101
```
Specify where to distribute routing information:
```
spine01(config-router)# neighbor 10.0.1.1 remote-as external
```
For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. Cumulus Linux enables the IPv4 address family by default; you do not need to run the activate command for IPv4 route exchange.
```
spine01(config-router)# neighbor 2001:db8:0002::0a00:0002 remote-as external
spine01(config-router)# address-family ipv6 unicast
spine01(config-router-af)# neighbor 2001:db8:0002::0a00:0002 activate
```
For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

Specify which prefixes to originate:

spine01(config-router)# address-family ipv4
spine01(config-router-af)# network 10.10.10.101/32
spine01(config-router-af)# end
spine01# write memory
spine01# exit

IPv6 prefixes:

spine01(config-router)# address-family ipv4
spine01(config-router-af)# network 2001:db8::101/128
spine01(config-router-af)# end
spine01# write memory
spine01# exit

When using auto BGP, there are no references to leaf or spine in the configurations. Auto BGP determines the ASN for the system and configures it using standard vtysh commands.

The vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@spine01:~$ sudo cat /etc/frr/frr.conf
...
router bgp 65199
 bgp router-id 10.10.10.101
 neighbor 10.0.1.1 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.101/32
 exit-address-family
...

BGP Unnumbered

The following example commands show a basic BGP unnumbered configuration for two switches, leaf01 and spine01, which are eBGP peers.

The only difference between a BGP unnumbered configuration and the BGP numbered configuration shown above is that the BGP neighbor is as an interface (instead of an IP address). You do not need to configure an IP address on the interface between the two peers on each side.

NVUE Commands

leaf01

cumulus@leaf01:~$ nv set router bgp autonomous-system 65101
cumulus@leaf01:~$ nv set router bgp router-id 10.10.10.1
cumulus@leaf01:~$ nv set vrf default router bgp neighbor swp51 remote-as external
cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.10.10.1/32
cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.1.10.0/24
cumulus@leaf01:~$ nv config apply

For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. Cumulus Linux enables the IPv4 address family by default; you do not need to run the activate command for IPv4 route exchange.

cumulus@leaf01:~$ nv set router bgp autonomous-system 65101
cumulus@leaf01:~$ nv set router bgp router-id 10.10.10.1
cumulus@leaf01:~$ nv set vrf default router bgp neighbor swp51 remote-as external
cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv6-unicast enable on
cumulus@leaf01:~$ nv set vrf default router bgp address-family ipv6-unicast network 2001:db8::1/128
cumulus@leaf01:~$ nv config apply

After you run nv config save, the NVUE Commands create the following configuration snippet in the /etc/nvue.d/startup.yaml file:

cumulus@leaf01:~$ sudo cat /etc/nvue.d/startup.yaml
...
- set:
    router:
      bgp:
        autonomous-system: 65101
        enable: on
        router-id: 10.10.10.1
    vrf:
      default:
        router:
          bgp:
            address-family:
              ipv4-unicast:
                enable: on
                network:
                  10.1.10.0/24: {}
                  10.10.10.1/32: {}
            enable: on
            neighbor:
              swp51:
                remote-as: external
                type: unnumbered

spine01

cumulus@spine01:~$ nv set router bgp autonomous-system 65199
cumulus@spine01:~$ nv set router bgp router-id 10.10.10.101
cumulus@spine01:~$ nv set vrf default router bgp neighbor swp1 remote-as external
cumulus@spine01:~$ nv set vrf default router bgp address-family ipv4-unicast network 10.10.10.101/32
cumulus@spine01:~$ nv config apply

cumulus@spine01:~$ nv set router bgp autonomous-system 65199
cumulus@spine01:~$ nv set router bgp router-id 10.10.10.101
cumulus@spine01:~$ nv set vrf default router bgp neighbor swp1 remote-as external
cumulus@spine01:~$ nv set vrf default router bgp address-family ipv6-unicast enable on
cumulus@spine01:~$ nv set vrf default router bgp address-family ipv6-unicast network 2001:db8::101/128
cumulus@spine01:~$ nv config apply

After you run nv config save, the NVUE Commands create the following configuration snippet in the /etc/nvue.d/startup.yaml file:

cumulus@spine01:~$ sudo cat /etc/nvue.d/startup.yaml
...
- set:
    router:
      bgp:
        autonomous-system: 65199
        enable: on
        router-id: 10.10.10.101
    vrf:
      default:
        router:
          bgp:
            address-family:
              ipv4-unicast:
                enable: on
                network:
                  10.10.10.101/32: {}
            enable: on
            neighbor:
              swp1:
                remote-as: external
                type: unnumbered

vtysh Commands

leaf01

cumulus@leaf01:~$ sudo vtysh
...
leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1
leaf01(config-router)# neighbor swp51 interface remote-as external
leaf01(config-router)# address-family ipv4
leaf01(config-router-af)# network 10.10.10.1/32
leaf01(config-router-af)# network 10.1.10.0/24
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit

cumulus@leaf01:~$ sudo vtysh
...
leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1
leaf01(config-router)# neighbor swp51 interface remote-as external
leaf01(config-router)# address-family ipv6 unicast
leaf01(config-router-af)# neighbor swp51 activate
leaf01(config-router-af)# network 2001:db8::1/128
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit

The vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@leaf01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65101
 bgp router-id 10.10.10.1
 neighbor swp51 interface remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.1/32
  network 10.1.10.0/24
 exit-address-family
...

spine01

cumulus@spine01:~$ sudo vtysh
...
spine01# configure terminal
spine01(config)# router bgp 65199
spine01(config-router)# bgp router-id 10.10.10.101
spine01(config-router)# neighbor swp1 interface remote-as external
spine01(config-router)# address-family ipv4
spine01(config-router-af)# network 10.10.10.101/32
spine01(config-router-af)# end
spine01# write memory
spine01# exit

cumulus@spine01:~$ sudo vtysh
...
spine01# configure terminal
spine01(config)# router bgp 65199
spine01(config-router)# bgp router-id 10.10.10.101
spine01(config-router)# neighbor swp1 interface remote-as external
spine01(config-router)# address-family ipv6 unicast
spine01(config-router-af)# neighbor swp1 activate
spine01(config-router-af)# network 2001:db8::101/128
spine01(config-router-af)# end
spine01# write memory
spine01# exit

The vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@spine01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65199
 bgp router-id 10.10.10.101
 neighbor swp1 interface remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.101/32
 exit-address-family
...

Verify Configuration

To verify that the switch can see its BGP neighbors, run the net show bgp summary command or the vtysh show ip bgp summary command:

leaf01

cumulus@leaf01:mgmt:~$ net show bgp summary
show bgp ipv4 unicast summary
=============================
BGP router identifier 10.10.10.1, local AS number 65101 vrf-id 0
BGP table version 3
RIB entries 5, using 1000 bytes of memory
Peers 1, using 23 KiB of memory

Neighbor        V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd   PfxSnt
spine01(swp51)  4      65199        54        55        0    0    0 00:02:29            1        3

Total number of neighbors 1
...

spine01

cumulus@spine01:mgmt:~$ net show bgp summary
show bgp ipv4 unicast summary
=============================
BGP router identifier 10.10.10.101, local AS number 65199 vrf-id 0
BGP table version 3
RIB entries 5, using 1000 bytes of memory
Peers 1, using 23 KiB of memory

Neighbor        V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd   PfxSnt
leaf01(swp1)    4      65101        73        73        0    0    0 00:03:25            2        3

Total number of neighbors 1
...

To verify that you can see the prefixes of the other neighbor in the routing table, run the net show route bgp command or the vtysh show ip route command.

leaf01

cumulus@leaf01:mgmt:~$ net show route bgp
RIB entry for bgp
=================
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure
B>* 10.10.10.101/32 [20/0] via fe80::4638:39ff:fe00:1, swp51, weight 1, 00:00:51

spine01

cumulus@spine01:mgmt:~$ net show route bgp
RIB entry for bgp
=================
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure
B>* 10.1.10.0/24 [20/0] via fe80::4638:39ff:fe00:2, swp1, weight 1, 00:00:11
B>* 10.10.10.1/32 [20/0] via fe80::4638:39ff:fe00:2, swp1, weight 1, 00:00:11

To configure optional BGP settings, see Optional BGP Configuration.
To view and test a full BGP configuration example, see Configuration Example.

Basic BGP Configuration

BGP Numbered

BGP Unnumbered

Verify Configuration

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Basic BGP Configuration

BGP Numbered

BGP Unnumbered

Verify Configuration

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