In this example I am going to present a very simple configuration example for advertising ipv6 prefixes over IPv4 ISP transport network. This method is called 6VPE where we do not need any dual stack configurations and the transport network doesn’t need to be ipv6 aware.
The whole concept becomes possible with the help of address-family in BGP. With the use of address family we advertise the prefixes , for the communication we don’t need to worry about l3 addresses(either Ipv4 or Ipv6) as it happens using labels in the core. Lets see the configuration below.
Tool used : GNS3 , Device used : Cisco IOSv Router
hostname CE-1-Site1
!
ipv6 unicast-routing
!
interface Loopback1
ip address 1.1.1.1 255.255.255.255
!
interface GigabitEthernet0/0
ip address 192.168.10.1 255.255.255.252
ipv6 address 2000::1/16
!
router bgp 200
bgp log-neighbor-changes
neighbor 2000::2 remote-as 100
neighbor 192.168.10.2 remote-as 100
!
address-family ipv6
network 2000::/16
neighbor 2000::2 activate
neighbor 2000::2 send-community
exit-address-family
hostname PE-1
!
vrf definition Cus1
rd 100:2
route-target export 100:2
route-target import 100:1
!
address-family ipv4
exit-address-family
!
address-family ipv6
exit-address-family
!
ipv6 unicast-routing
!
interface Loopback1
ip address 2.2.2.2 255.255.255.255
!
interface GigabitEthernet0/0
vrf forwarding Cus1
ip address 192.168.10.2 255.255.255.252
ipv6 address 2000::2/16
!
interface GigabitEthernet0/1
ip address 10.10.10.1 255.255.255.252
!
router ospf 1
mpls ldp autoconfig
router-id 2.2.2.2
network 0.0.0.0 255.255.255.255 area 0
!
router bgp 100
bgp router-id 2.2.2.2
bgp log-neighbor-changes
neighbor 4.4.4.4 remote-as 100
neighbor 4.4.4.4 update-source Loopback1
neighbor 2000::1 remote-as 200
!
address-family vpnv4
neighbor 4.4.4.4 activate
neighbor 4.4.4.4 send-community both
exit-address-family
!
address-family vpnv6
neighbor 4.4.4.4 activate
neighbor 4.4.4.4 send-community both
exit-address-family
!
address-family ipv6 vrf Cus1
neighbor 2000::1 remote-as 200
neighbor 2000::1 activate
neighbor 2000::1 send-community
exit-address-familyhostname P-Router
!
interface Loopback1
ip address 3.3.3.3 255.255.255.255
!
interface GigabitEthernet0/0
ip address 10.10.10.2 255.255.255.252
!
interface GigabitEthernet0/1
ip address 10.10.10.5 255.255.255.252
!
router ospf 1
mpls ldp autoconfig
router-id 3.3.3.3
network 0.0.0.0 255.255.255.255 area 0
!
hostname PE-2
!
vrf definition Cus1
rd 100:1
route-target export 100:1
route-target import 100:2
!
address-family ipv4
exit-address-family
!
address-family ipv6
exit-address-family
!
ipv6 unicast-routing
!
interface Loopback1
ip address 4.4.4.4 255.255.255.255
!
interface GigabitEthernet0/0
ip address 10.10.10.6 255.255.255.252
!
interface GigabitEthernet0/1
vrf forwarding Cus1
ip address 192.168.20.2 255.255.255.252
ipv6 address 2001::2/16
!
router ospf 1
mpls ldp autoconfig
router-id 4.4.4.4
network 0.0.0.0 255.255.255.255 area 0
!
router bgp 100
bgp router-id 4.4.4.4
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 update-source Loopback1
neighbor 2001::1 remote-as 500
!
address-family vpnv4
neighbor 2.2.2.2 activate
neighbor 2.2.2.2 send-community both
exit-address-family
!
address-family vpnv6
neighbor 2.2.2.2 activate
neighbor 2.2.2.2 send-community both
exit-address-family
!
address-family ipv6 vrf Cus1
neighbor 2001::1 remote-as 500
neighbor 2001::1 activate
neighbor 2001::1 send-community
exit-address-family
!hostname CE-1-Site2
!
ipv6 unicast-routing
!
interface Loopback1
ip address 5.5.5.5 255.255.255.255
!
interface GigabitEthernet0/0
ip address 192.168.20.1 255.255.255.252
ipv6 address 2001::1/16
!
router bgp 500
bgp log-neighbor-changes
neighbor 2001::2 remote-as 100
neighbor 192.168.20.2 remote-as 100
!
address-family ipv6
network 2001::/16
neighbor 2001::2 activate
neighbor 2001::2 send-community
exit-address-family
!Once the configuration is complete you can verify the working condition by pinging the end customer IPv6 IP addresses.
Also there are few BGP commands commands with which you can check if the prefixes are advertised.
CE-1-Site1#ping ipv6 2001::1 source 2000::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001::1, timeout is 2 seconds:
Packet sent with a source address of 2000::1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 6/9/12 ms
PE-1#sh bgp vpnv6 unicast vrf Cus1 summary BGP router identifier 2.2.2.2, local AS number 100 BGP table version is 10, main routing table version 10 2 network entries using 360 bytes of memory 2 path entries using 224 bytes of memory 3/2 BGP path/bestpath attribute entries using 504 bytes of memory 2 BGP AS-PATH entries using 48 bytes of memory 2 BGP extended community entries using 48 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 1184 total bytes of memory BGP activity 4/1 prefixes, 4/1 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 2000::1 4 200 115 116 10 0 0 01:39:45 1PE-1#sh bgp vpnv6 unicast vrf Cus1 BGP table version is 10, local router ID is 2.2.2.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, t secondary path, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not foundNetwork Next Hop Metric LocPrf Weight PathRoute Distinguisher: 100:2 (default for vrf Cus1) r> 2000::/16 2000::1 0 0 200 i *>i 2001::/16 ::FFFF:4.4.4.4 0 100 0 500 i
Now with ping working you must be curious to know how the packet is getting forwarded over the MPLS network. Here are echo request and echo response captured with the help of the wireshark.
Above packet captures clearly explain how the MPLS tags are making this communication possible.
Thank you for reading please feel free if you have any questions.
