Service Providers running an MPLS/IPv4 infrastructure follow the same trends, as several integration scenarios are possible to offer IPv6 services on an MPLS network. Cisco Systems specially developed IPv6 Provider Edge Router over MPLS—(Cisco 6PE) to meet all of those requirements.
Operation of 6PE
In the 6PE solution, the PE routers are dual-stack, which means they run IPv4 and IPv6. The CE routers that are running IPv6 are connected to the PE router via a normal interface; the interface is not part of a VRF for IPv6 even though the same interface might be in a VRF for IPv4. The IPv6 routing distribution between the PE routers is done via MP-iBGP. At the same time, MP-iBGP distributes the label to be used for the specific IPv6 prefixes. This BGP label identifies or tags the IPv6 packet at the egress PE. The egress PE looks up this BGP label in the label forwarding information base (LFIB) and uses it to forward the IPv6 packet toward the egress CE.
NOTE Notice that ipv6 unicast-routing and ipv6 cef are not enabled by default and thus must be configured. Also notice that RIP routing processes have names and that they have to be enabled on each interface.
The topology below shows the case:
CE config example:
ipv6 unicast-routing ipv6 cef ! interface Loopback0 ip address 10.100.1.1 255.255.255.255 ipv6 address 2001:DB8:11::1/128 ipv6 rip cust-one enable ! interface Ethernet0/1 description PE no ip address ipv6 address 2001:DB8:20::1/64 ipv6 rip cust-one enable ! ipv6 router rip cust-one ! end
PE - 254.1 config:
ip cef ipv6 unicast-routing ipv6 cef ! interface Loopback0 ip address 10.200.254.1 255.255.255.255 ! interface Ethernet0/0 ip address 10.200.200.1 255.255.255.0 mpls ip ! interface Ethernet0/1 description CE no ip address ipv6 address 2001:DB8:20::2/64 ipv6 enable ipv6 rip cust-one enable ! mpls ldp router-id Loopback0 force ! router ospf 1 mpls ldp autoconfig network 0.0.0.0 255.255.255.255 area 0 ! router bgp 1 bgp log-neighbor-changes no bgp default ipv4-unicast neighbor 10.200.254.7 remote-as 1 neighbor 10.200.254.7 update-source Loopback0 ! address-family ipv4 neighbor 10.200.254.7 activate exit-address-family ! address-family ipv6 redistribute connected redistribute rip cust-one neighbor 10.200.254.7 activate neighbor 10.200.254.7 send-community both neighbor 10.200.254.7 send-label exit-address-family ! ipv6 router rip cust-one redistribute bgp 1 ! end
Verifying 6PE Operation
CE# trace ipv6 2001:DB8:30::1
1 2001:DB8:20::2 0 msec 0 msec 0 msec 2 ::FFFF:10.200.200.2 [MPLS: Labels 17/20 Exp 0] 2 msec 2 msec 3 msec 3 ::FFFF:10.200.210.2 [MPLS: Labels 17/20 Exp 0] 2 msec 2 msec 2 msec 4 ::FFFF:10.200.211.2 [MPLS: Labels 17/20 Exp 0] 3 msec 3 msec 2 msec 5 ::FFFF:10.200.215.2 [MPLS: Labels 18/20 Exp 0] 2 msec 1 msec 2 msec 6 2001:DB8:30::2 2 msec 3 msec 2 msec 7 2001:DB8:30::1 3 msec 2 msec 2 msec
NOTE Notice the ::FFFF:IPv4 address notation in the traceroute. This is an IPv4-mapped IPv6 address, because it has the format of ::FFFF:IPv4-address. It represents the address of IPv4-only nodes as an IPv6 address. This is the result of this P router not having IPv6 enabled.
And after disable the ttl in MPLS cloud (no mpls ip propagate-ttl):
CE# trace ipv6 2001:DB8:30::1
1 2001:DB8:20::2 1 msec 0 msec 1 msec 2 2001:DB8:30::2 2 msec 2 msec 2 msec 3 2001:DB8:30::1 2 msec 2 msec 2 msec
CE# debug ipv6 rip
*May 31 18:48:59.515: RIPng [default VRF]: a message has been received. *May 31 18:48:59.515: RIPng [Et0/1, default VRF]: response received from FE80::A8BB:CCFF:FE00:1010 for process "cust-one". *May 31 18:48:59.515: src=FE80::A8BB:CCFF:FE00:1010 (Ethernet0/1) *May 31 18:48:59.515: dst=FF02::9 *May 31 18:48:59.515: sport=521, dport=521, length=72 *May 31 18:48:59.515: command=2, version=1, mbz=0, #rte=3 *May 31 18:48:59.515: tag=0, metric=1, prefix=2001:DB8:20::/64 *May 31 18:48:59.515: tag=0, metric=1, prefix=2001:DB8:30::/64 *May 31 18:48:59.515: tag=0, metric=2, prefix=2001:DB8:12::1/128 CE# *May 31 18:49:02.737: RIPng [Et0/1, default VRF]: process "cust-one" is sending a multicast update. *May 31 18:49:02.737: src=FE80::A8BB:CCFF:FE00:8010 *May 31 18:49:02.737: dst=FF02::9 (Ethernet0/1) *May 31 18:49:02.737: sport=521, dport=521, length=52 *May 31 18:49:02.737: command=2, version=1, mbz=0, #rte=2 *May 31 18:49:02.737: tag=0, metric=1, prefix=2001:DB8:11::1/128 *May 31 18:49:02.737: tag=0, metric=1, prefix=2001:DB8:20::/64 *May 31 18:49:02.737: RIPng [Lo0, default VRF]: process "cust-one" is sending a multicast update. *May 31 18:49:02.737: src=FE80::A8BB:CCFF:FE00:8000 *May 31 18:49:02.737: dst=FF02::9 CE# (Loopback0) *May 31 18:49:02.737: sport=521, dport=521, length=92 *May 31 18:49:02.737: command=2, version=1, mbz=0, #rte=4 *May 31 18:49:02.737: tag=0, metric=1, prefix=2001:DB8:11::1/128 *May 31 18:49:02.737: tag=0, metric=1, prefix=2001:DB8:20::/64 *May 31 18:49:02.737: tag=0, metric=2, prefix=2001:DB8:30::/64 *May 31 18:49:02.737: tag=0, metric=3, prefix=2001:DB8:12::1/128 *May 31 18:49:02.738: RIPng [default VRF]: a message has been received. *May 31 18:49:02.738: RIPng [Lo0, default VRF]: process "cust-one" received own response.
CE# show ipv6 route rip
R 2001:DB8:12::1/128 [120/3]
via FE80::A8BB:CCFF:FE00:1010, Ethernet0/1
R 2001:DB8:30::/64 [120/2]
via FE80::A8BB:CCFF:FE00:1010, Ethernet0/1
PE# show bgp ipv6 unicast neighbors
BGP neighbor is 10.200.254.7, remote AS 1, internal link BGP version 4, remote router ID 10.200.254.7 BGP state = Established, up for 02:34:15 Last read 00:00:19, last write 00:00:30, hold time is 180, keepalive interval is 60 seconds Neighbor sessions: 1 active, is not multisession capable (disabled) Neighbor capabilities: Route refresh: advertised and received(new) Four-octets ASN Capability: advertised and received Address family IPv4 Unicast: advertised and received Address family IPv6 Unicast: advertised and received ipv6 MPLS Label capability: advertised and received Enhanced Refresh Capability: advertised and received ... For address family: IPv6 Unicast Session: 10.200.254.7 BGP table version 7, neighbor version 7/0 Output queue size : 0 Index 2, Advertise bit 0 2 update-group member Community attribute sent to this neighbor Sending Prefix & Label ...
PE# show ipv6 route 2001:db8:30::1
Routing entry for 2001:DB8:30::/64 Known via "bgp 1", distance 200, metric 0, type internal Redistributing via rip cust-one Route count is 1/1, share count 0 Routing paths: 10.200.254.7%default indirectly connected MPLS label: 20 Last updated 02:37:44 ago
PE# show bgp ipv6 unicast 2001:db8:30::1/64
BGP routing table entry for 2001:DB8:30::/64, version 6 Paths: (1 available, best #1, table default) Not advertised to any peer Refresh Epoch 1 Local ::FFFF:10.200.254.7 (metric 51) from 10.200.254.7 (10.200.254.7) Origin incomplete, metric 0, localpref 100, valid, internal, best mpls labels in/out nolabel/20 rx pathid: 0, tx pathid: 0x0
PE# show ipv6 cef 2001:DB8:30::1/64 detail
2001:DB8:30::/64, epoch 0, flags [rib defined all labels] recursive via 10.200.254.7 label 20 nexthop 10.200.200.2 Ethernet0/0 label 17
Summary Steps
1. enable
2. configure terminal
3. ip cef
4. ipv6 cef
5. ipv6 unicast-routing
6. router bgp as-number
7. no synchronization
8. no bgp default ipv4-unicast
9. neighbor {ip-address | ipv6-address | peer-group-name} remote-as as-number
10. neighbor {ip-address | ipv6-address | peer-group-name} update-so intf-type intf-number
11. address-family ipv6
12. neighbor {ip-address | ipv6-address | peer-group-name} activate
13. neighbor {ip-address | ipv6-address | peer-group-name} send-label
14. exit-address-family
biOos
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