address families

Pre-Alpha. This page describes behavior that may change.

Address families in Ze fall into two groups. IPv4 and IPv6 unicast and multicast are built into the engine. Everything else (EVPN, FlowSpec, VPN, BGP-LS, labelled unicast, VPLS, MVPN, RTC, MUP) is provided by an nlri plugin, and is only available when the plugin is loaded. This page lists what ships and how to enable each one.

Built into the engine

These four families work without any plugin.

Family	Config name	AFI / SAFI
IPv4 Unicast	ipv4/unicast	1 / 1
IPv6 Unicast	ipv6/unicast	2 / 1
IPv4 Multicast	ipv4/multicast	1 / 2
IPv6 Multicast	ipv6/multicast	2 / 2

Enable them under peer { family { } }:

peer upstream {
    connection { remote { ip 10.0.0.1; } }
    session {
        asn { remote 65001; }
        family {
            ipv4/unicast { prefix { maximum 1000000; } }
            ipv6/unicast { prefix { maximum 200000; } }
        }
    }
}

Every enabled family requires a prefix { maximum }. That is RFC 4486 and Ze refuses to start without it.

Plugin-provided families

The rest ship as bgp-nlri-* plugins. Run ze --plugins to list the ones compiled into your binary.

Family	Config name	Plugin	Encode	Decode
IPv4 VPN	ipv4/mpls-vpn	bgp-nlri-vpn	Yes	Yes
IPv6 VPN	ipv6/mpls-vpn	bgp-nlri-vpn	Yes	Yes
IPv4 FlowSpec	ipv4/flow	bgp-nlri-flowspec	Yes	Yes
IPv6 FlowSpec	ipv6/flow	bgp-nlri-flowspec	Yes	Yes
IPv4 FlowSpec VPN	ipv4/flow-vpn	bgp-nlri-flowspec	Yes	Yes
IPv6 FlowSpec VPN	ipv6/flow-vpn	bgp-nlri-flowspec	Yes	Yes
IPv4 MPLS Label	ipv4/mpls-label	bgp-nlri-labeled	Yes	Yes
IPv6 MPLS Label	ipv6/mpls-label	bgp-nlri-labeled	Yes	Yes
L2VPN EVPN	l2vpn/evpn	bgp-nlri-evpn	Yes	Yes
L2VPN VPLS	l2vpn/vpls	bgp-nlri-vpls	Yes	Yes
BGP-LS	bgp-ls/bgp-ls	bgp-nlri-ls	No	Yes
BGP-LS VPN	bgp-ls/bgp-ls-vpn	bgp-nlri-ls	No	Yes
IPv4 MVPN	ipv4/mvpn	bgp-nlri-mvpn	No	Yes
IPv6 MVPN	ipv6/mvpn	bgp-nlri-mvpn	No	Yes
IPv4 RTC	ipv4/rtc	bgp-nlri-rtc	No	Yes
IPv4 MUP	ipv4/mup	bgp-nlri-mup	Yes	Yes
IPv6 MUP	ipv6/mup	bgp-nlri-mup	Yes	Yes

The "Encode" and "Decode" columns are worth reading carefully. BGP-LS, MVPN, and RTC are decode-only: Ze parses received NLRIs for these families but does not encode them. If you need to send routes in those families, Ze is not the answer.

Enabling a plugin-provided family

All NLRI plugins are internal and loaded automatically. List the family under peer { family { } }.

bgp {
    peer upstream {
        connection { remote { ip 10.0.0.1; } }
        session {
            asn { remote 65001; }
            family {
                ipv4/unicast { prefix { maximum 1000000; } }
                l2vpn/evpn   { prefix { maximum 10000;   } }
            }
        }
    }
}

If the family is listed but the plugin is not loaded, Ze fails to start with an error naming the unknown family. The error is at load time, not at runtime, so you catch it before peering.

Capability negotiation

Ze advertises every enabled family in the Multiprotocol Extensions capability (RFC 4760) during OPEN. The session only negotiates the families both peers advertise. If the local side lists ipv4/unicast and ipv6/unicast and the peer lists only ipv4/unicast, only ipv4/unicast is active.

The peer <name> capabilities command shows the negotiated result after the session is up.

ze# peer upstream capabilities
capabilities {
    four-octet-asn       yes
    route-refresh        yes
    add-path             yes
    graceful-restart     yes
    extended-message     yes
    families [ ipv4/unicast ipv6/unicast ]
}

Prefix limits per family

Every enabled family on every peer has its own prefix { maximum }, and its own optional warning threshold.

family {
    ipv4/unicast  { prefix { maximum 1000000; warning 900000; } }
    ipv6/unicast  { prefix { maximum 200000;  warning 180000; } }
    ipv4/mpls-vpn { prefix { maximum 500; } }
    l2vpn/evpn    { prefix { maximum 10000; } }
}

The warning defaults to 90% of maximum when not set. When the received prefix count crosses the warning threshold upward, the BGP reactor pushes a bgp/prefix-threshold warning onto the operational report bus, which shows up in ze show warnings and on the CLI login banner. When the count crosses the maximum, the session is torn down with NOTIFICATION Cease/MaxPrefixes (subcode 1) unless teardown false is set.

See peers for the full prefix limit reference.

Extended next-hop

RFC 8950 Extended Next Hop lets you advertise IPv4 NLRI with an IPv6 next-hop or vice versa. Ze supports it through the nexthop capability leaf.

capability {
    nexthop {
        ipv4/unicast ipv6;
        ipv4/unicast ipv4;
    }
}

This is what you want when you need IPv4 forwarding over an IPv6-only peering session.

See also

• BGP peers for the surrounding peer configuration.
• Plugins: address families for the per-plugin reference.
• In-tree BGP protocol features for the full authoritative table.

Adapted from main/docs/features/bgp-protocol.md and main/docs/guide/configuration.md.