Consider the following network topology:
I am using the IPv6 address space 2001:dead:beef:0:0:0:0:0/64 (2001:dead:beef:0::/64) to create the subnets that I will use to address these routers. I have decided that the subnet 2001:dead:beef::0/112 will be reserved for the loopback addresses on my core routers (far more than I need, but in real-life, that would provide room for expansion in the future). The subnet 2001:dead:beef::1:0/112 will be reserved -- and subdivided -- for point-to-point networks, such as the serial links between the core routers. Each LAN will be a /112 on 2001:dead:beef::x:0, where "x" is greater than 0 -- for example, 2001:dead:beef::1:0/112, 2001:dead:beef::2:0/112, etc. I will use OPSFv6 to route between these various networks.
As I often do, I am using Cisco 3600-series routers for the core routers (ANCCR1, ENACR1, FAICR1 and HOMCR1) and Cisco 2600-series routers to simulate PCs attached to the routers' LANs. Since the 2600 routers are the simplest to configure -- just a single Ethernet interface and a static route to the core routers -- that's where I started configuring this network:
faipc2(config)#int fa1/0
faipc2(config-if)#description Uplink to faicr1
faipc2(config-if)#ipv6 address 2001:dead:beef:0:0:0:3:2/112
faipc2(config-if)#ipv6 enable
faipc2(config-if)#no shut
faipc2(config-if)#exit
faipc2(config)#ipv6 route 0:0:0:0:0:0:0:0/0 2001:dead:beef:0:0:0:3:1
faipc2(config)#
That's all it takes to configure an IPv6 address on FA1/0 and to set up a static route to faicr1. We'll repeat this set-up (with the appropriate IPv6 addresses and routes, of course) on R5-R9, but I won't duplicate the configurations here.
Once the "PC's" are configured, we'll start configuring the core routers. Let's start with anccr1, since it's the most complex router on the network, having two Ethernet interfaces, two serial interfaces and a loopback interface:
anccr1(config)#int lo0
anccr1(config-if)#ipv6 address 2001:dead:beef::1/128
anccr1(config-if)#ipv6 enable
anccr1(config-if)#no shut
anccr1(config-if)#int fa1/0
anccr1(config-if)#desc Anchorage LAN 1
anccr1(config-if)#ipv6 address 2001:dead:beef::6:1/112
anccr1(config-if)#ipv6 enable
anccr1(config-if)#no shut
anccr1(config-if)#int fa2/0
anccr1(config-if)#desc Anchorage LAN 2
anccr1(config-if)#ipv6 address 2001:dead:beef::7:1/112
anccr1(config-if)#ipv6 enable
anccr1(config-if)#no shut
anccr1(config-if)#int s0/0
anccr1(config-if)#desc Uplink to faicr1
anccr1(config-if)#ipv6 address 2001:dead:beef::1:1/127
anccr1(config-if)#ipv6 enable
anccr1(config-if)#no shut
anccr1(config-if)#int s0/1
anccr1(config-if)#desc Uplink to enacr1
anccr1(config-if)#ipv6 address 2001:dead:beef::1:5/127
anccr1(config-if)#ipv6 enable
anccr1(config-if)#no shut
Just as in IPv4, by default, the router will know how to reach connected networks, but will not share routes with the other routers until a routing protocol (OSPF, BGP, EIGRP, etc.) is enabled. However, at this point we should have two devices we can reach from anccr1: ancpc1 (R7 on the diagram) and ancpc2 (R8 on the diagram). Let's try to ping them both:
anccr1#ping 2001:dead:beef::6:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::6:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/7/12 ms
anccr1#ping 2001:dead:beef::7:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::7:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/12 ms
anccr1#
Excellent! We were able to ping both hosts. Let's turn up enacr1 and see if we can ping across the serial link:
enacr1(config)#int fa1/0
enacr1(config-if)#desc Kenai LAN
enacr1(config-if)#ipv6 address 2001:dead:beef::4:1/112
enacr1(config-if)#ipv6 enable
enacr1(config-if)#no shut
enacr1(config-if)#int s0/1
enacr1(config-if)#desc Uplink to homcr1
enacr1(config-if)#ipv6 address 2001:dead:beef::1:9/127
enacr1(config-if)#ipv6 enable
enacr1(config-if)#no shut
enacr1(config-if)#int s0/0
enacr1(config-if)#desc Uplink to anccr1
enacr1(config-if)#ipv6 address 2001:dead:beef::1:6/127
enacr1(config-if)#ipv6 enable
enacr1(config-if)#no shut
Hmmm...something seems to be wrong. I can ping the 2600 router ("LAN PC"), but not the Anchorage core router:
enacr1#ping 2001:dead:beef::1:5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::1:5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
enacr1#ping 2001:dead:beef::4:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::4:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/6/12 ms
enacr1#
We'll troubleshoot just like we would on an IPv4 network:
enacr1#sho ipv6 int brief
Serial0/0 [up/up]
FE80::CE02:14FF:FEA2:10
2001:dead:beef::1:6
Serial0/1 [up/up]
FE80::CE02:14FF:FEA2:10
2001:dead:beef::1:9
Serial0/2 [administratively down/down]
unassigned
Serial0/3 [administratively down/down]
unassigned
FastEthernet1/0 [up/up]
FE80::CE02:14FF:FEA2:10
2001:dead:beef::4:1
enacr1#
enacr1#sho ipv6 route
IPv6 Routing Table - 8 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
C 2001:dead:beef::1:6/127 [0/0]
via ::, Serial0/0
L 2001:dead:beef::1:6/128 [0/0]
via ::, Serial0/0
C 2001:dead:beef::1:8/127 [0/0]
via ::, Serial0/1
L 2001:dead:beef::1:9/128 [0/0]
via ::, Serial0/1
C 2001:dead:beef::4:0/112 [0/0]
via ::, FastEthernet1/0
L 2001:dead:beef::4:1/128 [0/0]
via ::, FastEthernet1/0
L FE80::/10 [0/0]
via ::, Null0
L FF00::/8 [0/0]
via ::, Null0
enacr1#
Hmmm...well, for one thing, we configured the IPv6 addresses on the serial ports as /127's on both routers rather than /126's. In theory, this should work, but you might want to research /127's on an IPv6 network before using them. For now, let's change the /127's to /126's, and see what happens:
anccr1#ping 2001:dead:beef::1:6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::1:6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/16 ms
anccr1#
That's better! I'd love to say that the incorrect subnetting was an accidental typo, but in all honesty...I fubar'd the notation -- but it made for a great teaching moment, so I didn't edit it out of the blog entry, lol.
One last thing to try...by default, a router knows all of the subnets connected to it, and the "LAN PC's" have a default route to the local core router, so in theory, a "LAN PC" should be able to ping the loopback IPv6 address of its local LAN router. Let's try it:
ancpc1#ping 2001:dead:beef::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/8 ms
ancpc1#
Sweet! That worked just as expected.
Now, let's try enabling routing on the IPv6 network:
homcr1(config)#ipv6 router ospf 42
% IPv6 routing not enabled
homcr1(config)#
Eh?!?! A quick search of the magic Google ball explains why: you must enable IPv6 unicast routing before you can turn up any IPv6 routing protocols. <shrug> Okay, whatever. Let's do it:
homcr1(config)#ipv6 unicast-routing
homcr1(config)#ipv6 router ospf 42
04:44:40: %OSPFv3-4-NORTRID: OSPFv3 process 42 could not pick a router-id,
please configure manually
Ummm...okay. I was just about to do that, anyway:
homcr1(config-rtr)#router-id 2001:dead:beef::4
^
% Invalid input detected at '^' marker.
And we wonder why IPv6 is taking so long to adopt, sigh. According to the spec, the OSPF router ID is technically NOT an IP address, but is instead a 32-bit number that is used to uniquely identify the router in it's OSPF area. Since IP (v4) addresses happen to also be 32-bit numbers, that is what is typically used, but it is not a requirement. The fact that Cisco, by default, will select one of the IPv4 addresses configured on the router to use as the router ID if you do not manually specify one muddies the issue, but that isn't really relevant here...except that we haven't configured any IPv4 addresses on the router, so OSPF can't arbitrarily snatch one to use as the router ID. Back on track...let's assign a random 32-bit router ID to this router:
homcr1(config-rtr)#router-id 4.4.4.4
Next, there is no "network a.b.c.d e.f.g.h area i.j.k.l" command in IPv6 OSPF like there is in IPv4 OSPF. Instead, we set the OSPF area globally, and tell the OSPF process what we would like to distribute:
homcr1(config-rtr)#area 0.0.0.0 range 2001:dead:beef::0/64
homcr1(config-rtr)#redistribute connected
However, that isn't sufficient to start sharing routes via IPv6 OSPF:
faicr1#sho 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
LC 2001:dead:beef::3/128 [0/0]
via ::, Loopback0
C 2001:dead:beef::1:0/126 [0/0]
via ::, Serial0/0
L 2001:dead:beef::1:2/128 [0/0]
via ::, Serial0/0
C 2001:dead:beef::2:0/112 [0/0]
via ::, FastEthernet1/0
L 2001:dead:beef::2:1/128 [0/0]
via ::, FastEthernet1/0
C 2001:dead:beef::3:0/112 [0/0]
via ::, FastEthernet2/0
L 2001:dead:beef::3:1/128 [0/0]
via ::, FastEthernet2/0
L FE80::/10 [0/0]
via ::, Null0
L FF00::/8 [0/0]
via ::, Null0
faicr1#
In IPv6 OSPF, you have to enable the OSPF process in each interface that will be participating in OSPF:
faicr1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
faicr1(config)#int s0/0
faicr1(config-if)#ipv6 ospf 42 area 0.0.0.0
faicr1(config-if)#exit
05:10:00: %OSPFv3-5-ADJCHG: Process 42, Nbr 1.1.1.1 on Serial0/0 from LOADING to FULL, Loading Done
faicr1(config)#exit
faicr1#sho ipv6 route
IPv6 Routing Table - 16 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
OE2 2001:dead:beef::1/128 [110/20]
via FE80::CE01:14FF:FEA2:10, Serial0/0
OE2 2001:dead:beef::2/128 [110/20]
via FE80::CE01:14FF:FEA2:10, Serial0/0
LC 2001:dead:beef::3/128 [0/0]
via ::, Loopback0
C 2001:dead:beef::1:0/126 [0/0]
via ::, Serial0/0
L 2001:dead:beef::1:2/128 [0/0]
via ::, Serial0/0
O 2001:dead:beef::1:4/126 [110/128]
via FE80::CE01:14FF:FEA2:10, Serial0/0
O 2001:dead:beef::1:8/126 [110/192]
via FE80::CE01:14FF:FEA2:10, Serial0/0
C 2001:dead:beef::2:0/112 [0/0]
via ::, FastEthernet1/0
L 2001:dead:beef::2:1/128 [0/0]
via ::, FastEthernet1/0
C 2001:dead:beef::3:0/112 [0/0]
via ::, FastEthernet2/0
L 2001:dead:beef::3:1/128 [0/0]
via ::, FastEthernet2/0
OE2 2001:dead:beef::4:0/112 [110/20]
via FE80::CE01:14FF:FEA2:10, Serial0/0
OE2 2001:dead:beef::6:0/112 [110/20]
via FE80::CE01:14FF:FEA2:10, Serial0/0
OE2 2001:dead:beef::7:0/112 [110/20]
via FE80::CE01:14FF:FEA2:10, Serial0/0
L FE80::/10 [0/0]
via ::, Null0
L FF00::/8 [0/0]
via ::, Null0
faicr1#
That's much better! Now we have routes from the other routers (which previously had OSPF enabled on their serial interfaces) showing up on the Fairbanks core router. Let's make sure our "LAN PC's&qout; can ping end-to-end:
hompc1#ping 2001:dead:beef::4:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::4:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/13/20 ms
hompc1#ping 2001:dead:beef::6:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::6:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/36/64 ms
hompc1#ping 2001:dead:beef::7:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::7:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/30/56 ms
hompc1#ping 2001:dead:beef::2:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::2:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/35/56 ms
hompc1#ping 2001:dead:beef::3:2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:dead:beef::3:2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/25/57 ms
hompc1#
