Ticket #07

Ticket #07

Network diagram

IGP diagram


The problem:

R2 can't ping to R1's Lo0 IPv6 address from all of its interfaces. Fix the problem.

The solution:

First, lets try to ping to R1's Lo0 IPv6 address from R2's interfaces.


On R2:

R2#ping ipv6 fc00:99::1 source fastEthernet 0/1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FC00:99::1, timeout is 2 seconds:
Packet sent with a source address of FC00:24::2
..
Success rate is 0 percent (0/2)
R2#ping ipv6 fc00:99::1 source lo0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FC00:99::1, timeout is 2 seconds:
Packet sent with a source address of FC00:99::2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/12 ms

As we can see, R2 can ping to R1's Lo0 from its Lo0 interface, but can't do so from its FastEthernet0/1interface.


Maybe R1 has no route back to all of R2's interfaces. Lets have a look at R1's routing table entries.

On R1:

R1#sh ipv route fc00:99::2
Routing entry for FC00:99::2/128
  Known via "ospf 1", distance 110, metric 20, type extern 2
  Route count is 1/1, share count 0
  Routing paths:
    FE80::C803:46FF:FE4C:8, FastEthernet0/0
      Last updated 05:01:26 ago

R1#sh ipv route fc00:24::2
% Route not found

We can see that for R2's Lo0 IPv6 address, R1 has an external OSPFv3 route via R4, but for R2's FastEthernet0/1 IPv6 address, R1 got no route back.


Maybe R1 has a default route?

On R1:

R1#sh ipv6 route 0::0/0
% Route not found

No default route either.


Lets move closer to R2, from R1's perspective. Maybe R4 have no route to R2's FastEthernet0/1 IPv6 address?

On R4:

R4#sh ipv6 route fc00:24::2
Routing entry for FC00:24::/64
  Known via "connected", distance 0, metric 0, type connected
  Backup from "eigrp 24 [90]"
  Route count is 1/1, share count 0
  Routing paths:
    directly connected via FastEthernet0/1
      Last updated 05:11:13 ago

The route to R2's FastEthernet0/1 is a connected route.


Lets sum up what we know:

  • R2 can't ping to R1's Lo0 IPv6 address from its FastEthernet0/1 interface, but can do so from its Lo0 interface.
  • R1 have an external OSPFv3 route to R2's Lo0 but no route to R2's FastEthernet0/1.

How R1 could get external OSPFv3 route to R2's Lo0? R4 must be redistributing. Lets check it out.

On R4:

R4#sh run | sec ipv6 router ospf
ipv6 router ospf 1
 router-id 4.4.4.4
 log-adjacency-changes
 redistribute eigrp 24

We can see that R4 is redistributing EIGRP routes. We can also see that no filtering was configured. Then why R4 isn't also redistributing its FastEthernet0/1 IPv6 route, as it is also part of EIGRP?


Lets have a closer look at R4's redistribution command.

On R4:

R4(config)#ipv6 router ospf 1
R4(config-rtr)#redistribute eigrp 24 ?
  include-connected  Include connected
  metric             Metric for redistributed routes
  metric-type        OSPF/IS-IS exterior metric type for redistributed routes
  route-map          Route map reference
  tag                Set tag for routes redistributed into OSPF
  <cr>

Unlike IPv4 (except ISIS), when we redistribute routes in IPv6, the connected routes are not redistributed automatically. We need to manually configure the router to also include the connected routes when it redistributes from one routing protocol to the other.


Lets configure R4 to include connected routes when it redistribute from EIGRP to OSPFv3.

On R4:

R4(config)#ipv6 router ospf 1
R4(config-rtr)#redistribute eigrp 24 include-connected

Lets go back to R1 and check if we have a route to R2's FastEthernet0/1 IPv6 address.

On R1:

R1#sh ipv route fc00:24::2
Routing entry for FC00:24::/64
  Known via "ospf 1", distance 110, metric 20, type extern 2
  Route count is 1/1, share count 0
  Routing paths:
    FE80::C803:46FF:FE4C:8, FastEthernet0/0
      Last updated 00:01:13 ago

Now R1 have a route back to R2's FastEthernet0/1 IPv6 address. Lets try again to ping from R2's FastEthernet0/1 to R1's Lo0.

On R2:

R2#ping ipv6 fc00:99::1 source fastEthernet 0/1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to FC00:99::1, timeout is 2 seconds:
Packet sent with a source address of FC00:24::2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/8 ms

Success!

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