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Router sending multicast traffic without PIM configure

Hi, everyone

I have 3 routers connected as follow:

R1 -(.34 )--(5.5.128.32/27)--(.33)- R2 ---(.2 )--(5.5.128.0/27)--(.1)--- R3

R2 have pim sparse-mode and it is the AutoRP and Mapping Agent

R1 have pim-sparse-mode and the loopback interface is igmp-join to group 239.100.100.1

R3 do not have PIM configure and is the source of multicast traffic

When R3 ping to the multicast group 239.100.100.1, it's be receive response.

Reply to request 96 from 5.5.128.1, 100 ms

Reply to request 97 from 5.5.128.1, 168 ms

Reply to request 98 from 5.5.128.1, 108 ms

Reply to request 99 from 5.5.128.1, 56 ms

Reply to request 96 from 5.5.128.1, 100 ms
Reply to request 97 from 5.5.128.1, 168 ms
Reply to request 98 from 5.5.128.1, 108 ms
Reply to request 99 from 5.5.128.1, 56 ms
R3#

follow the output of something's shows:

---------ROUTER1-----------------------

R1#sh ip int brief | e una
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            5.5.128.1       YES NVRAM  up                    up
Loopback0                  5.5.1.1         YES NVRAM  up                    up
R1#

R1#sh ip pim interface

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
5.5.1.1          Loopback0                v2/S   0      30     1      5.5.1.1
5.5.128.1        FastEthernet0/0          v2/S   1      30     1      5.5.128.2
R1#

R1#sh run | i multicast|pim

ip multicast-routing

ip pim sparse-mode

ip pim sparse-mode

R1#

R1#sh ip pim int count

State: * - Fast Switched, D - Distributed Fast Switched
       H - Hardware Switching Enabled
Address          Interface                FS  Mpackets In/Out
5.5.1.1          Loopback0                *   0/0
5.5.128.1        FastEthernet0/0          *   919/0
R1#


R1#sh ip pim rp mapping
PIM Group-to-RP Mappings

Group(s) 224.0.0.0/4
  RP 5.5.2.2 (?), v2v1
    Info source: 5.5.2.2 (?), elected via Auto-RP
         Uptime: 00:27:55, expires: 00:02:49
R1#

R1#sh ip mroute 239.100.100.1
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
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.100.100.1), 02:49:38/stopped, RP 5.5.2.2, flags: SJCL
  Incoming interface: FastEthernet0/0, RPF nbr 5.5.128.2
  Outgoing interface list:
    Loopback0, Forward/Sparse, 02:49:38/00:02:08

(5.5.128.34, 239.100.100.1), 00:00:03/00:02:59, flags: LJT
  Incoming interface: FastEthernet0/0, RPF nbr 5.5.128.2
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:00:03/00:02:56

R1#

R1#sh ip cef

Prefix              Next Hop             Interface

0.0.0.0/0           drop                 Null0 (default route handler entry)

0.0.0.0/32          receive

5.5.1.0/24          attached             Loopback0

5.5.1.0/32          receive

5.5.1.1/32          receive

5.5.1.255/32        receive

5.5.2.2/32          5.5.128.2            FastEthernet0/0

5.5.3.3/32          5.5.128.2            FastEthernet0/0

5.5.128.0/27        attached             FastEthernet0/0

5.5.128.0/32        receive

5.5.128.1/32        receive

5.5.128.2/32        5.5.128.2            FastEthernet0/0

5.5.128.31/32       receive

5.5.128.32/27       5.5.128.2            FastEthernet0/0

224.0.0.0/4         0.0.0.0

224.0.0.0/24        receive

255.255.255.255/32  receive

R1#

R2#sh ip cef

Prefix              Next Hop             Interface

0.0.0.0/0           drop                 Null0 (default route handler entry)

0.0.0.0/32          receive

5.5.1.1/32          5.5.128.1            FastEthernet0/1

5.5.2.2/32          receive

5.5.3.3/32          5.5.128.34           FastEthernet0/0

5.5.128.0/27        attached             FastEthernet0/1

5.5.128.0/32        receive

5.5.128.1/32        5.5.128.1            FastEthernet0/1

5.5.128.2/32        receive

5.5.128.31/32       receive

5.5.128.32/27       attached             FastEthernet0/0

5.5.128.32/32       receive

5.5.128.33/32       receive

5.5.128.34/32       5.5.128.34           FastEthernet0/0

5.5.128.63/32       receive

224.0.0.0/4         0.0.0.0

224.0.0.0/24        receive

255.255.255.255/32  receive

R2#

R3#

R3#sh ip cef

Prefix              Next Hop             Interface

0.0.0.0/0           drop                 Null0 (default route handler entry)

0.0.0.0/32          receive

5.5.1.1/32          5.5.128.33           FastEthernet0/0

5.5.2.2/32          5.5.128.33           FastEthernet0/0

5.5.3.3/32          receive

5.5.128.0/27        5.5.128.33           FastEthernet0/0

5.5.128.32/27       attached             FastEthernet0/0

5.5.128.32/32       receive

5.5.128.33/32       5.5.128.33           FastEthernet0/0

5.5.128.34/32       receive

5.5.128.63/32       receive

224.0.0.0/4         drop

224.0.0.0/24        receive

255.255.255.255/32  receive

R3#

R3#

R1#sh ip cef
Prefix              Next Hop             Interface
0.0.0.0/0           drop                 Null0 (default route handler entry)
0.0.0.0/32          receive
5.5.1.0/24          attached             Loopback0
5.5.1.0/32          receive
5.5.1.1/32          receive
5.5.1.255/32        receive
5.5.2.2/32          5.5.128.2            FastEthernet0/0
5.5.3.3/32          5.5.128.2            FastEthernet0/0
5.5.128.0/27        attached             FastEthernet0/0
5.5.128.0/32        receive
5.5.128.1/32        receive
5.5.128.2/32        5.5.128.2            FastEthernet0/0
5.5.128.31/32       receive
5.5.128.32/27       5.5.128.2            FastEthernet0/0
224.0.0.0/4         0.0.0.0
224.0.0.0/24        receive
255.255.255.255/32  receive
R1#

---------ROUTER2-----------------------

R2#sh ip int brief | e una
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            5.5.128.33      YES manual up                    up
FastEthernet0/1            5.5.128.2       YES manual up                    up
Loopback0                  5.5.2.2         YES NVRAM  up                    up
R2#sh ip pim inter

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
5.5.2.2          Loopback0                v2/S   0      30     1      5.5.2.2
5.5.128.2        FastEthernet0/1          v2/S   1      30     1      5.5.128.2
5.5.128.33       FastEthernet0/0          v2/S   0      30     1      5.5.128.33
R2#

R2#
R2#sh run | i multicast|pim
ip multicast-routing
ip pim sparse-mode
ip pim sparse-mode
ip pim sparse-mode
ip pim send-rp-announce Loopback0 scope 3
ip pim send-rp-discovery Loopback0 scope 3
R2#
R2#sh ip pim int coun
R2#sh ip pim int count

State: * - Fast Switched, D - Distributed Fast Switched
       H - Hardware Switching Enabled
Address          Interface                FS  Mpackets In/Out
5.5.2.2          Loopback0                *   352/0
5.5.128.2        FastEthernet0/1              0/1631
5.5.128.33       FastEthernet0/0              2202/0
R2#
R2#sh ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent (Loopback0)

Group(s) 224.0.0.0/4
  RP 5.5.2.2 (?), v2v1
    Info source: 5.5.2.2 (?), elected via Auto-RP
         Uptime: 02:54:24, expires: 00:02:31
R2#

R2#sh ip mroute 239.100.100.1
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
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 239.100.100.1), 00:32:54/00:03:27, RP 5.5.2.2, flags: S
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse, 00:32:54/00:03:27

(5.5.128.34, 239.100.100.1), 00:03:45/00:03:07, flags: T
  Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0
  Outgoing interface list:
    FastEthernet0/1, Forward/Sparse, 00:03:45/00:03:27

R2#

R2#sh ip cef
Prefix              Next Hop             Interface
0.0.0.0/0           drop                 Null0 (default route handler entry)
0.0.0.0/32          receive
5.5.1.1/32          5.5.128.1            FastEthernet0/1
5.5.2.2/32          receive
5.5.3.3/32          5.5.128.34           FastEthernet0/0
5.5.128.0/27        attached             FastEthernet0/1
5.5.128.0/32        receive
5.5.128.1/32        5.5.128.1            FastEthernet0/1
5.5.128.2/32        receive
5.5.128.31/32       receive
5.5.128.32/27       attached             FastEthernet0/0
5.5.128.32/32       receive
5.5.128.33/32       receive
5.5.128.34/32       5.5.128.34           FastEthernet0/0
5.5.128.63/32       receive
224.0.0.0/4         0.0.0.0
224.0.0.0/24        receive
255.255.255.255/32  receive
R2#

---------ROUTER3-----------------------

R3#
R3#sh ip int brief | e una
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            5.5.128.34      YES NVRAM  up                    up
Loopback0                  5.5.3.3         YES NVRAM  up                    up
R3#sh ip pim inter

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
R3#

R3#
R3#sh ip cef
Prefix              Next Hop             Interface
0.0.0.0/0           drop                 Null0 (default route handler entry)
0.0.0.0/32          receive
5.5.1.1/32          5.5.128.33           FastEthernet0/0
5.5.2.2/32          5.5.128.33           FastEthernet0/0
5.5.3.3/32          receive
5.5.128.0/27        5.5.128.33           FastEthernet0/0
5.5.128.32/27       attached             FastEthernet0/0
5.5.128.32/32       receive
5.5.128.33/32       5.5.128.33           FastEthernet0/0
5.5.128.34/32       receive
5.5.128.63/32       receive
224.0.0.0/4         drop
224.0.0.0/24        receive
255.255.255.255/32  receive
R3#

                 

Now can see the show of capture traffic for a ICMP packet to a multicast destination address:

No.     Time        Source                Destination           Protocol Info
   3380 4000.624000 5.5.128.34            239.100.100.1         ICMP     Echo (ping) request

Frame 3380 (114 bytes on wire, 114 bytes captured)
    Arrival Time: Jun 12, 2012 18:24:57.747521000
    [Time delta from previous captured frame: 0.296000000 seconds]
    [Time delta from previous displayed frame: 0.296000000 seconds]
    [Time since reference or first frame: 4000.624000000 seconds]
    Frame Number: 3380
    Frame Length: 114 bytes
    Capture Length: 114 bytes
    [Frame is marked: False]
    [Protocols in frame: eth:ip:icmp:data]
    [Coloring Rule Name: ICMP]
    [Coloring Rule String: icmp || icmpv6]
Ethernet II, Src: c2:02:0e:b0:00:00 (c2:02:0e:b0:00:00), Dst: IPv4mcast_64:64:01 (01:00:5e:64:64:01)
    Destination: IPv4mcast_64:64:01 (01:00:5e:64:64:01)
        Address: IPv4mcast_64:64:01 (01:00:5e:64:64:01)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
    Source: c2:02:0e:b0:00:00 (c2:02:0e:b0:00:00)
        Address: c2:02:0e:b0:00:00 (c2:02:0e:b0:00:00)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
    Type: IP (0x0800)
Internet Protocol, Src: 5.5.128.34 (5.5.128.34), Dst: 239.100.100.1 (239.100.100.1)
    Version: 4
    Header length: 20 bytes
    Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
        0000 00.. = Differentiated Services Codepoint: Default (0x00)
        .... ..0. = ECN-Capable Transport (ECT): 0
        .... ...0 = ECN-CE: 0
    Total Length: 100
    Identification: 0x08c7 (2247)
    Flags: 0x00
        0.. = Reserved bit: Not Set
        .0. = Don't fragment: Not Set
        ..0 = More fragments: Not Set
    Fragment offset: 0
    Time to live: 255
    Protocol: ICMP (0x01)
    Header checksum: 0xda44 [correct]
        [Good: True]
        [Bad : False]
    Source: 5.5.128.34 (5.5.128.34)
    Destination: 239.100.100.1 (239.100.100.1)
Internet Control Message Protocol
    Type: 8 (Echo (ping) request)
    Code: 0 ()
    Checksum: 0xcdff [correct]
    Identifier: 0x003a
    Sequence number: 6 (0x0006)
    Data (72 bytes)

0000  00 00 00 00 01 f2 ae 18 ab cd ab cd ab cd ab cd   ................
0010  ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd   ................
0020  ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd   ................
0030  ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd   ................
0040  ab cd ab cd ab cd ab cd                           ........
        Data: 0000000001F2AE18ABCDABCDABCDABCDABCDABCDABCDABCD...
        [Length: 72]

I need to know why the router 3 can send multicast traffic if it not have PIM enable, not have ip multicast-routing enable and CEF table say that it must be drop the traffic..????

I find the following information on Cisco Documentacion:

According to IPv4 multicast standards, the MAC destination multicast address begins with 0100:5e and is appended by the last 23 bits of the IP address. On the Catalyst 3750 switch, if the multicast packet does not match the switch multicast address, the packets are treated in this way:

If the packet has a multicast IP address and a unicast MAC address, the packet is forwarded in software. This can occur because some protocols on legacy devices use unicast MAC addresses with multicast IP addresses.

If the packet has a multicast IP address and an unmatched multicast MAC address, the packet is dropped.

source: http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_52_se/configuration/guide/swmcast.html#wp1150712

The 3 Routers are hardware emulate (GNS3):

R3#sh ver
Cisco IOS Software, 3700 Software (C3725-ADVENTERPRISEK9-M), Version 12.4(15)T11, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Wed 28-Oct-09 22:57 by prod_rel_team

ROM: ROMMON Emulation Microcode
ROM: 3700 Software (C3725-ADVENTERPRISEK9-M), Version 12.4(15)T11, RELEASE SOFTWARE (fc2)

R3 uptime is 9 hours, 44 minutes
System returned to ROM by unknown reload cause - suspect boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19
System image file is "tftp://255.255.255.255/unknown"


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use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

Cisco 3725 (R7000) processor (revision 0.1) with 124928K/6144K bytes of memory.
Processor board ID FTX0945W0MY
R7000 CPU at 240MHz, Implementation 39, Rev 2.1, 256KB L2, 512KB L3 Cache
2 FastEthernet interfaces
DRAM configuration is 64 bits wide with parity enabled.
55K bytes of NVRAM.
16384K bytes of ATA System CompactFlash (Read/Write)

Configuration register is 0x2102

R3#
R3#
R3#
R3#
R3#

Thank in advance for you assistance.

DS

1 REPLY
Hall of Fame Super Silver

Re: Router sending multicast traffic without PIM configure

Hello David,

the packets are process switched because they are locally generated, There is no need to be part of the PIM cloud to generate ICMP packets with a multicast destination. The behaviour should be to send out the ICMP request out of all interfaces on R3, so there is a chance to reach the other routers and the IGMP join on the other router allows to receive ICMP replies.

Hope to help

Giuseppe

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