Advertising IPv6 Prefixes/Routes Over IPv4 EBGP Peers

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Dec 5, 2011 4:03 AM
Dec 5th, 2011


Introduction

As defined in RFC 2283, a BGP speaker has capability of carrying routing information for multiple network layer protocols (e.g., IPv6, IPX, etc..). In this configuration example, we are routing IPv6 traffic over preestablished IPv4 EBGP connection.

Requirements
  • Understanding on BGP
  • IPv6 Addressing Scheme

Background

In this document, interface Fast Ethernet [0/0] of routers R1 and R2 are establishing EBGP peering. The two routers are in two different autonomous systems 100 and 200. The loopback interface (loopback 10) is assigned with IPv6 address and it is required to advertise these addresses over IPv4 EBGP peers. In the process it is important to set the IPv6 Next-Hop, in this scenario a route-map is configured to set the Next-Hop [command set ipv6 next-hop] .Or if you don’t want to use IPv6 addresses on the direct link, one has to configure a tunnel to have a valid and reachable ipv6 Next-Hop.

Note: All configurations is tested in a lab environment on Cisco 2811 router running IOS C2800NM-ADVENTERPRISEK9, Version 12.4(15)T14.

Topology Diagram

IPv6 Over Ipv4 Topo.bmp

Configuration

Router R1Router R2

hostname R1

ip cef

ipv6 unicast-routing

interface Loopback10

  no ip address

  ipv6 address 2011:ABC:12E:121::1/64

  ipv6 enable

interface FastEthernet0/0

  ip address 17.17.17.1 255.255.255.0

duplex auto

speed auto

ipv6 address 2011::1/64

ipv6 enable

router bgp 100

  bgp router-id 1.1.1.1

  bgp log-neighbor-changes

  neighbor 17.17.17.2 remote-as 200

  neighbor 17.17.17.2 ebgp-multihop 5

  address-family ipv4

   neighbor 17.17.17.2 activate

   no auto-summary

   no synchronization

   network 17.17.17.1 mask 255.255.255.255

  exit-address-family

  address-family ipv6

   neighbor 17.17.17.2 activate

   neighbor 17.17.17.2 route-map IPv6-NextHop out

   network 2011:ABC:12E:121::/64

  exit-address-family

route-map IPv6-NextHop permit 10

  set ipv6 next-hop 2011::1

end

hostname R2

ip cef

ipv6 unicast-routing

interface Loopback10

  no ip address

  ipv6 address 3011:ABC:12E:122::1/64

  ipv6 enable

interface FastEthernet0/0

  ip address 17.17.17.2 255.255.255.0

  duplex auto

  speed auto

  ipv6 address 2011::2/64

  ipv6 enable

router bgp 200

  bgp router-id 2.2.2.2

  bgp log-neighbor-changes

  neighbor 17.17.17.1 remote-as 100

  neighbor 17.17.17.1 ebgp-multihop 5

  address-family ipv4

   neighbor 17.17.17.1 activate

   no auto-summary

   no synchronization

   network 17.17.17.2 mask 255.255.255.255

  exit-address-family

  address-family ipv6

   neighbor 17.17.17.1 activate

   neighbor 17.17.17.1 route-map IPv6-NextHop out

   network 3011:ABC:12E:122::/64

  exit-address-family

route-map IPv6-NextHop permit 10

  set ipv6 next-hop 2011::2

end

Verification

On Router R1

R1#show ipv6 route

IPv6 Routing Table - 6 entries

Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP

        U - Per-user Static route, M - MIPv6

        I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary

        O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2

        ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2

        D - EIGRP, EX - EIGRP external

C   2011::/64 [0/0]

      via ::, FastEthernet0/0

L   2011::1/128 [0/0]

      via ::, FastEthernet0/0

C   2011:ABC:12E:121::/64 [0/0]

      via ::, Loopback10

L   2011:ABC:12E:121::1/128 [0/0]

      via ::, Loopback10

B   3011:ABC:12E:122::/64 [20/0]

      via 2011::2

L   FF00::/8 [0/0]

      via ::, Null0

R1#show bgp ipv6 unicast

BGP table version is 3, local router ID is 1.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

               r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 2011:ABC:12E:121::/64::                       0         32768 i

*> 3011:ABC:12E:122::/64            2011::2                  0             0 200 i

As seen from the above output, the IPv6 prefix 3011:ABC:12E:122::/64 is being learn by Router R1.

R1#ping ipv6

Target IPv6 address: 3011:ABC:12E:122::1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands? [no]: y

Source address or interface: 2011:ABC:12E:121::1

UDP protocol? [no]:

Verbose? [no]:

Precedence [0]:

DSCP [0]:

Include hop by hop option? [no]:

Include destination option? [no]:

Sweep range of sizes? [no]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 3011:ABC:12E:122::1, timeout is 2 seconds:

Packet sent with a source address of 2011:ABC:12E:121::1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

References

Implementing Multiprotocol BGP for IPv6

Cisco IOS IPv6 Command Reference

IPv6 Tunnel through an IPv6 Network

Cisco: IP Version 6 (IPv6) Support Page

IPv6 Frequently Asked Questions

Routing IPv6 over IPv4

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