H3C Technologies H3C S5560 Series Switches - Manual (Page 214)

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BGP-4 cannot carry routing information for multiple network layer protocols.
To support multiple network layer protocols, MP-BGP defines the following path attributes:
• MP_REACH_NLRI—Carries feasible route prefixes and next hops for multiple network layer
protocols.
• MP_UNREACH_NLRI—Carries unfeasible route prefixes for multiple network layer protocols.
MP-BGP uses these two attributes to advertise feasible and unfeasible routes for different network layer
protocols. BGP speakers not supporting MP-BGP ignore updates containing these attributes and do not
forward them to its peers.
The current MP-BGP implementation supports multiple protocol extensions, including VPN, IPv6, and
multicast. For more information about VPN, see MPLS Configuration Guide.
Address family
MP-BGP uses address families and subsequent address families to identify different network layer
protocols for routes contained in the MP_REACH_NLRI and MP_UNREACH_NLRI attributes. For example,
an Address Family Identifier (AFI) of 2 and a Subsequent Address Family Identifier (SAFI) of 1 identify
IPv6 unicast routing information carried in the MP_REACH_NLRI attribute. For address family values, see
RFC 1700.
BGP configuration views
BGP uses different views to manage routing information for different address families and different VPN
instances. Most BGP commands are available in all BGP views. BGP supports multiple VPN instances by
establishing a separate routing table for each VPN instance.
Table 14 describes different BGP configuration views.
Table 14 BGP configuration views
View names Ways to enter the views Remarks
BGP view
system-view
[Sysname] bgp 100
[Sysname-bgp]
Configurations in this view apply to
all address families of the public
network and all VPN instances (such
as confederation, GR, and logging
configurations), or apply to all
address families of the public
network.
BGP IPv4 unicast address
family view
system-view
[Sysname] bgp 100
[Sysname-bgp] address-family
ipv4 unicast
[Sysname-bgp-ipv4]
Configurations in this view apply to
IPv4 unicast routes and peers on the
public network.
BGP IPv6 unicast address
family view
system-view
[Sysname] bgp 100
[Sysname-bgp] address-family
ipv6 unicast
[Sysname-bgp-ipv6]
Configurations in this view apply to
IPv6 unicast routes and peers on the
public network.