Dell SmartFabric OS10 User Guide Release 10.5.3

BGP unnumbered

The BGP unnumbered feature supports route exchange for advertising IPv4 NLRI with IPv6 next-hop.

Dell Technologies recommends populating the next hop field as follows:

• The IPv6 address of the next hop is followed by the link-local IPv6 address of the next hop. This field is constructed following recommendations that are described in Constructing the Next Hop field.

In SmartFabric OS10 implementations enter the global IPv6 address in the Next Hop field, if it is configured in the peer interface; otherwise, enter the default IPv6 address in the Next Hop field. The IPv6 address is followed by the link-local address.

After receiving route-updates from an unnumbered peer with link-local address entered in both fields of Next Hop, SmartFabric OS10 brings down the unnumbered session that is formed with the FRR-based switch. All outgoing route updates are sent with the global IPv6 address followed by the link-local address in the Next hop field of the BGP UPDATE message. This is the default behavior of route exchange between unnumbered peers that are established with FRR vendors.

This feature introduces the link-local-only-nexthop command, to enable interoperability with such nonstandard implementations. You can configure the link-local-only-nexthop command at the following three levels: ROUTER BGP, BGP neighbor, and BGP template. When you enable this feature, route-updates are accepted when both fields of the Next Hop are filled with link-local addresses. This feature also enables route updates to be sent with link-local addresses entered in both fields of Next Hop.