Concept Guide

Congure IPv6 NH Automatically for IPv6 Prex Advertised
over IPv4 Neighbor
You can congure the system to pick the next hop IPv6 address dynamically for IPv6 prex advertised over an IPv4 neighbor congured
under IPv6 address family. If there is no IPv6 address congured on the local interface, the system uses the IPv4 mapped IPv6 address. If
there are multiple IPv6 addresses congured on the interface, the system uses the lowest IPv6 address congured on that interface. If the
conguration is already present and a new IPv6 address, which is lower than the lowest existing address, is assigned to one of the peer
interfaces, that address is not used as the NH until you ap the interface manually.
Figure 26. Congure IPv6 NH to advertise IPv6 prex over IPv4 neighbor
To enable BGP to pick the next hop IPv6 address automatically for IPv6 prex advertised over an IPv4 neighbor, use the following
commands.
• Enable the system to pick the next hop IPv6 address dynamically for IPv6 prex advertised over an IPv4 neighbor.
ROUTER-BGP mode mode
neighbor {ip–address | peer-group-name} auto-local-address
Enter either the neighbor IP address or the name of the peer group.
NOTE
: If outbound policy is applied along with auto-local-address enabled, then policy takes precedence.
Example conguration of BGP to automatically pick IPv6 address automatically for IPv6 prex advertised over an IPv4 neighbor
The following example conguration demonstrates how to congure BGP to automatically pick IPv6 address for IPv6 prex advertised over
an IPv4 neighbor.
Example conguration performed in R1
DellEMC# configure terminal
DellEMC(conf)# router bgp 655
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 remote-as 20
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 auto-local-address
DellEMC(conf-router_bgp)# neighbor 10.1.1.2 no shutdown
DellEMC(conf-router_bgp)# bgp router-id 1.1.1.1
DellEMC(conf-router_bgp)# address-family ipv6 unicast
DellEMC(conf-router_bgpv6_af)# neighbor 10.1.1.2 activate
DellECM(conf-router_bgpv6_af)# exit
Conguring the auto-local-address for a neighbor will dynamically pick the local BGP interface IPv6 address (2001::1/64) as a the next hop
for all the updates over IPv4 neighbor congured under IPv6 address family. If the auto-local-address is not congured, the IPv4 mapped
IPv6 address (10.1.1.1) as a next hop.
Following is the show running-config command output for the above conguration.
DellEMC# show running-config bgp
!
router bgp 655
Border Gateway Protocol (BGP)
241