MBGP vs BGP

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MBGP vs BGP

Currently BGP is running in version 4, which has been published in 2006 (RFC 4271). By default, BGPv4 only supports IPv4 unicast prefixes, But BGP can do much more than carrying IPv4 prefixes only. RFC 4760 Multiprotocol extensions for BGPv4 was written in order to enhance the capacity of carrying routing related information other than carrying ipv4 only.
  
Multiprotocol Extensions for BGPv4 added some new attributes.
·         Multiprotocol Reachable NLRI (MP_REACH_NLRI): It carry set of reachable destination with next-hop information.
·         Multiprotocol Unreachable NLRI (MP_UNREACH_NLRI): It carry set of unreachable destinations.
 
Note: - “MP_REACH_NLRI” and “MP_UNREACH_NLRI” are optional and Non-transitive attribute, because of this if neighbor doesn’t support the multiprotocol capabilities, it will just ignore information carried in these attributes and will not pass it to other BGP neighbor.
 
Both “MP_REACH_NLRI” and “MP_UNREACH_NLRI” contains two fields.
·         Address family identifier (AFI): use for identifies address types.
 
Example to check MBGP AFI types
R1(config)#router bgp 65001
R1(config-router)# address-family ?
ipv4            Address family
ipv6            Address family
l2vpn          Address family
rtfilter         Address family
vpnv4        Address family
vpnv6        Address family
 
·         Subsequent address family identifier (SAFI):  Use for provide further address family information.
 
Example to check MBGP SAFI types
R1(config-router)#address-family ipv4 ?
mdt                  Address Family modifier
multicast          Address Family modifier
mvpn               Address Family modifier
unicast            Address Family modifier
vrf                    Specify parameters for a VPN Routing/Forwarding instance
 
 
Multiprotocol BGP address family types
·         Unicast: - IPv4, IPv6
·         Multicast: - IPv4, IPv6
·         Virtualization: - VPNv4, VPNv6, L2VPN, VPLS, MCAST-VPN, MDT, Encapsulation, Tunnel, 4over6, 6over4.
 
 
MBGP configuration Example
Step 1: - First define address family under BGP configuration.
R1(config-router)#address-family {ipv4 | ipv6} {Unicast | Multicast}
 
Step 2: - Activate neighbor session.
R1(config-router-af)#neighbor {ipv6-address| IPv6-address | Peer-group-name} activate
 
Step 3: - Configure policies and networks.
Example of IPv4 unicast address family
R1(config-router)#address-family ipv4 unicast
R1(config-router-af)#network <IPv4-address> mask <Subnetmask>
 
Step 4: - exit address family configuration.
R1(config-router-af)#exit-address-family

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