IPv6 Static Routes
Now that we have laid the foundation for IPv6 addressing and basic services, the next section of
this chapter focuses on routing. This section begins with static routes and then covers the two IPv6
routing protocols on the CCIE Routing and Switching qualifying exam blueprint, OSPFv3 and
IPv6 EIGRP.
Static routing in IPv6 works almost exactly as it does in IPv4, but with several twists:
■ An IPv6 static route to an interface has a metric of 1, not 0 as in IPv4.
■ An IPv6 static route to a next-hop IP address also has a metric of 1, like IPv4.
■ Floating static routes work the same way in IPv4 and IPv6.
■ An IPv6 static route to a broadcast interface type, such as Ethernet, must also specify a nexthop
IPv6 address, for reasons covered next.
As mentioned in the preceding list, IPv6 static routes that point to a broadcast interface must also
specify a next-hop IP address. This is because, as you will recall from earlier in this chapter, IPv6
does not use ARP, and, therefore, there is no concept of proxy ARP for IPv6. A next-hop router
will not proxy for a destination that is off the subnet. Therefore, static routes must specify the nexthop
IP address in situations where you specify a broadcast interface as a next hop.
One valuable tip for real-life configuration work, especially where time is of the essence (as it is
in the CCIE lab exam): Before you begin configuring routing processes or static routes, enable
IPv6 routing debugging using the debug ipv6 routing command. This has the benefit of showing
you all changes to the IPv6 routing table, including any that you may not intend!
Example 20-7 shows the configuration of a sample IPv6 static route and how it looks in the routing
table.
Example 20-7 IPv6 Static Route Configuration and show Commands
Martin(config)# ipv6 route 2001:129::/64 2001::207:85FF:FE80:7208
Martin(config)# end
Martin#
Apr 2 19:22:30.191: %SYS-5-CONFIG_I: Configured from console by console
Martin# show ipv6 route
IPv6 Routing Table - 9 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route
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 2001::/64 [0/0]
via ::, Serial0/0
L 2001::207:85FF:FE80:71B8/128 [0/0]
via ::, Serial0/0
C 2001:128::/64 [0/0]
via ::, Loopback0
L 2001:128::1/128 [0/0]
via ::, Loopback0
C 2001:128:1F:633::/64 [0/0]
via ::, FastEthernet0/0
L 2001:128:1F:633:207:85FF:FE80:71B8/128 [0/0]
via ::, FastEthernet0/0
S 2001:129::/64 [1/0]
via 2001::207:85FF:FE80:7208
L FE80::/10 [0/0]
via ::, Null0
L FF00::/8 [0/0]
via ::, Null0
Martin# ping 2001:129::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:129::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/30/32 ms
Martin#
Note in the output in Example 20-7 that the router automatically generates a /128 route in the IPv6
routing table, classified as Local, for each of its own interfaces.
A floating static route is configured in the same way as shown in Example 20-7, but floating static
routes also include the administrative distance after the next hop. The full syntax of the ipv6 route
command is included in the Cisco IOS command table at the end of this chapter. Additionally, you
will find more detail on IPv6 static routing in the multicast coverage at the end of this chapter.