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Cumulus Linux

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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.

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.
  • Assign a router ID, which is a 32-bit value and is typically the address of the loopback interface on the switch.
  • 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.

  1. 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.

  2. Assign the router ID.

    cumulus@leaf01:~$ nv set router bgp router-id 10.10.10.1

  3. 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.

  4. 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

  1. 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.

  2. Assign the router ID.

    cumulus@spine01:~$ nv set router bgp router-id 10.10.10.101

  3. 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.

  4. 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

  1. Enable the bgpd daemon as described in FRRouting.

  2. Identify the BGP node by assigning an ASN and the router ID:

    cumulus@leaf01:~$ sudo vtysh
...
leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1

  3. 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.

  4. 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

  1. Enable the bgpd daemon as described in FRRouting.

  2. Identify the BGP node by assigning an ASN and the router ID:

    cumulus@spine01:~$ sudo vtysh
...
spine01# configure terminal
spine01(config)# router bgp 65199
spine01(config-router)# bgp router-id 10.10.10.101

  3. 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.

  4. 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.

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

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

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 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

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

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:~$ 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
...

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

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:~$ 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
...

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