Ticket #04

Ticket #04

Network diagram

IGP diagram


The problem:
R2 has joined to the 239.2.2.2 group. R4 Can't ping to that address. Fix the problem.

The solution:

First, lets try to ping to 239.2.2.2 from R4.

On R4:

R4#ping 239.2.2.2

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 239.2.2.2, timeout is 2 seconds:
.

Indeed, R4 can't reach the 239.2.2.2 group.


Lets make sure that R2 is actually listening to 239.2.2.2, by pinging to that group from R2 itself, and by checking the IGMP group membership.

On R2:

R2#ping 239.2.2.2

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 239.2.2.2, timeout is 2 seconds:

Reply to request 0 from 9.13.12.2, 4 ms
Reply to request 0 from 9.13.100.2, 4 ms
R2#sh ip igmp groups 
IGMP Connected Group Membership
Group Address    Interface                Uptime    Expires   Last Reporter   Group Accounted
239.2.2.2        Loopback0                04:08:27  00:02:36  9.13.100.2      
224.0.1.40       Loopback0                04:08:27  00:02:33  9.13.100.2      

R2 is listening to 239.2.2.2 and answering to it.

Lets make sure that R4 have a unicast connectivity with R2's Lo IP address.

On R4:

R4#ping 9.13.100.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 9.13.100.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/14/20 ms              

R4 has unicast reachability with R2's Lo0.


Our next step will be to map the multicast network. We shell start with mapping PIM interfaces, while making sure the PIM mode is in sync throught the network, and there is a PIM path between R4 and R2.

On R4:

R4#sh ip pim neighbor 
PIM Neighbor Table
Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority,
      S - State Refresh Capable
Neighbor          Interface                Uptime/Expires    Ver   DR
Address                                                            Prio/Mode
9.13.45.5         FastEthernet0/1          04:17:56/00:01:42 v2    1 / DR S P

We can see that PIM is enabled on R4 towards R5, which is in the path to R2. All neighbors are in sparse-mode


Notice that we are using show ip pim neighbor command, and not show ip pim interface command, because we also check if we have PIM connectivity with the next hop towards R2.


Lets move on to R5.

On R5:

R5#sh ip pim ne
PIM Neighbor Table
Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority,
      S - State Refresh Capable
Neighbor          Interface                Uptime/Expires    Ver   DR
Address                                                            Prio/Mode
9.13.15.1         FastEthernet0/0          04:27:43/00:01:42 v2    1 / S P
9.13.45.4         FastEthernet0/1          04:27:43/00:01:31 v2    1 / S P

PIM is enabled on R5 interfaces facing towards R4 and towards R2, via R1. On both interface R5 has found sparse-mode neighbors.


Lets move on to R1.

On R1:

R1#sh ip pim neighbor
PIM Neighbor Table
Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority,
      S - State Refresh Capable
Neighbor          Interface                Uptime/Expires    Ver   DR
Address                                                            Prio/Mode
9.13.15.5         FastEthernet0/0          04:35:23/00:01:33 v2    1 / DR S P

On R1, only the on interface facing R4, via R5 we can see a PIM neighbor. Where is R2? Lets check the PIM interface table on R1.

On R1:

R1#sh ip pim int

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
9.13.100.1       Loopback0                v2/S   0      30     1      9.13.100.1
9.13.15.1        FastEthernet0/0          v2/S   1      30     1      9.13.15.5

PIM is not enabled on the interface facing R2! If PIM is not enabled on the link between R1 and R2, it can be a major problem for R4 to get to R2. Lets fix that.

On R1:

R1(config)#int f0/1
R1(config-if)#ip pim sparse-mode
R1(config-if)#
*Dec  1 15:13:03.958: %PIM-5-NBRCHG: neighbor 9.13.12.2 UP on interface FastEthernet0/1 
*Dec  1 15:13:04.086: %PIM-5-DRCHG: DR change from neighbor 0.0.0.0 to 9.13.12.2 on interface FastEthernet0/1

Now R1 is a PIM neighbor with R2. Lets complete the mapping and move on to R2.

On R2:

R2#sh ip pim neighbor 
PIM Neighbor Table
Mode: B - Bidir Capable, DR - Designated Router, N - Default DR Priority,
      S - State Refresh Capable
Neighbor          Interface                Uptime/Expires    Ver   DR
Address                                                            Prio/Mode
9.13.12.1         FastEthernet0/1          00:02:27/00:01:15 v2    1 / S P
R2#sh ip pim interface

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
9.13.100.2       Loopback0                v2/S   0      30     1      9.13.100.2
9.13.12.2        FastEthernet0/1          v2/S   1      30     1      9.13.12.2

We can see that R2 is neighbor with R1, towards R4, and that PIM is also enabled on R2's Lo0, where its listening to 239.2.2.2.


Now that we have found a problem with missing PIM interface command and fixed it, lets check again if R4 can reach the 239.2.2.2 group.

On R4:

R4#ping 239.2.2.2     

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 239.2.2.2, timeout is 2 seconds:
.

Its still isn't working. Lets go back to mapping the mulitcast network.


We have finished to map and fix the PIM interface, now we need to map the RP mappings in the network. Lets start with R4.

R4:

R4#sh ip pim rp mapping
PIM Group-to-RP Mappings

Group(s): 224.0.0.0/4, Static
    RP: 9.13.100.1 (?)

R4 is configured with a static RP of 9.13.100.1, which is R1's Lo0 IP address. Lets make sure the rest of the network have the same mappings.

On R5:

R5#sh ip pim rp mapping
PIM Group-to-RP Mappings

Group(s): 224.0.0.0/4, Static
    RP: 9.13.100.1 (?)

R1's Lo0 IP address is statically configured as the RP for R5.


R5 got the same RP mappings as R4. Lets move on to R1.

On R1:

*Dec  1 16:22:24.858: %PIM-6-INVALID_RP_JOIN: Received (*, 239.2.2.2) Join from 9.13.12.2 for invalid RP 9.13.100.1
R1#sh ip pim rp mapping
PIM Group-to-RP Mappings

R1#

We can see that R1, which was configured as the RP on R4 and R5, is not configured with an RP address! And we can also see the console messages on R1, that indicates that it got a (*,G),RP join to unknown RP, which happens to be R1's Lo0 IP address.

Lets fix R1 and configure it to be the RP.

On R1:

R1(config)#ip pim rp-address 9.13.100.1

Now lets try again to ping from R4 to the 239.2.2.2 group, but first lets verify that R1 got the (*,239.2.2.2),RP join from R2.

On R1:

R1#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
       L - Local, P - Pruned, R - RP-bit set, F - Register flag,
       T - SPT-bit set, J - Join SPT, M - MSDP created entry,
       X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
       U - URD, I - Received Source Specific Host Report,
       Z - Multicast Tunnel, z - MDT-data group sender,
       Y - Joined MDT-data group, y - Sending to MDT-data group,
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.2.2.2), 00:01:25/00:03:03, RP 9.13.100.1, flags: S
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse, 00:01:25/00:03:03

(*, 224.0.1.40), 06:00:12/00:02:51, RP 9.13.100.1, flags: SJCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse, 00:00:27/00:03:02
    FastEthernet0/0, Forward/Sparse, 00:00:35/00:02:54
    Loopback0, Forward/Sparse, 06:00:12/00:02:51

Now that we see and (*,G),RP for 239.2.2.2, we can now try to ping from R4 to the 239.2.2.2 group.

On R4:

R4#ping 239.2.2.2       

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 239.2.2.2, timeout is 2 seconds:

Reply to request 0 from 9.13.12.2, 28 ms

Success!

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