PIX/ASA 7.x: Multicast on the PIX/ASA Platforms with Sender on Outside Configuration Example

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Updated:September 26, 2008
Document ID:71779

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Introduction

This document provides a sample configuration for multicast on the Cisco Adaptive Security Appliance (ASA) and/or PIX Security Appliance that runs version 7.x. In this example, the multicast sender is on the outside of the security appliance and hosts on the inside are attempting to receive the multicast traffic. The hosts send IGMP reports to report group membership, and the firewall uses Protocol Independent Multicast (PIM) sparse mode as the dynamic multicast routing protocol to the upstream router, behind which the source of the stream resides.

Note: FWSM/ASA does not support 232.x.x.x/8 subnet as a group number as it is reserved for ASA SSM. So FWSM/ASA does not allow this subnet to be used or traversed and mroute does not get created. But, you can still pass this multicast traffic through ASA/FWSM if you encapsulate it in GRE tunnel.

Prerequisites

Requirements

A Cisco PIX or ASA Security Appliance that runs software version 7.0, 7.1, or 7.2.

Components Used

The information in this document is based on a Cisco PIX or Cisco ASA Firewall that runs version 7.x.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Background Information

PIX/ASA 7.x introduces full PIM sparse mode and bi-directional support for dynamic multicast routing through the firewall. PIM dense mode is not supported. The 7.x software still supports legacy multicast 'stub-mode' in which the firewall is simply an IGMP proxy between interfaces as was supported in PIX version 6.x.

These statements hold true for multicast traffic through the firewall:

  • If an access-list is applied to the interface where the multicast traffic is received, then the access control list (ACL) must explicitly permit the traffic. If no access-list is applied to the interface, the explicit ACL entry that permits the multicast traffic is not necessary.

  • The multicast data packets are always subjected to the Reverse Path Forwarding check of the firewall, regardless of whether the reverse-path forward check command is configured on the interface. Therefore, if there is no route on the interface that the packet was received on to the source of the multicast packet, then the packet is dropped.

  • If there is no route on the interface back to the source of the multicast packets, use the mroute command to instruct the firewall not to drop the packets.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.

Network Diagram

This document uses this network setup.

The multicast traffic is sourced from 192.168.1.2 and uses UDP packets on port 1234 destined to group 224.1.2.3.

pix-asa-multicast-outside-1.gif

Configuration

This document uses this configuration:

Cisco PIX or ASA Firewall that runs Version 7.x 
maui-soho-01#show running-config 
 SA Version 7.1(2)
!
hostname ciscoasa
enable password 8Ry2YjIyt7RRXU24 encrypted


 
!--- The multicast-routing command enables IGMP and PIM !--- on all interfaces of the firewall. 

multicast-routing
names
!
interface Ethernet0/0
 nameif outside
 security-level 0
 ip address 172.16.1.1 255.255.255.0
!
interface Ethernet0/1
 nameif inside
 security-level 100
 ip address 10.0.0.1 255.255.255.0
!
interface Ethernet0/2
 no nameif
 no security-level
 no ip address
!
interface Ethernet0/3
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Management0/0
 shutdown
 no nameif
 no security-level
 no ip address
!
passwd 2KFQnbNIdI.2KYOU encrypted


!--- The rendezvous point address must be defined in the !--- configuration in order for PIM to function correctly.

pim rp-address 172.16.1.2
boot system disk0:/asa712-k8.bin
ftp mode passive

!--- It is necessary to permit the multicast traffic with an !--- access-list entry.

access-list outside_access_inbound extended permit ip any host 224.1.2.3
pager lines 24
logging enable
logging buffered debugging
mtu outside 1500
mtu inside 1500
no failover

!--- The access-list that permits the multicast traffic is applied !--- inbound on the outside interface.

access-group outside_access_inbound in interface outside


!--- This mroute entry specifies that the multicast sender !--- 192.168.1.2 is off the outside interface. In this example !--- the mroute entry is necessary since the firewall has no route to !--- the 192.168.1.2 host on the outside interface. Otherwise, this !--- entry is not necessary.

mroute 192.168.1.2 255.255.255.255 outside
icmp permit any outside
asdm image disk0:/asdm521.bin
no asdm history enable
arp timeout 14400
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00
timeout mgcp-pat 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
telnet timeout 5
ssh timeout 5
console timeout 0
!
class-map inspection_default
 match default-inspection-traffic
!
!
policy-map global_policy
 class inspection_default
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect rsh
  inspect rtsp
  inspect esmtp
  inspect sqlnet
  inspect skinny
  inspect sunrpc
  inspect xdmcp
  inspect sip
  inspect netbios
  inspect tftp
!
service-policy global_policy global
!
end

Verify

Use this section to confirm that your configuration works properly.

The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

  • show mroute—Displays the IPv4 multicast routing table.

    ciscoasa#show mroute 

Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group,
       C - Connected, L - Local, I - Received Source Specific Host Report,
       P - Pruned, R - RP-bit set, F - Register flag, T - SPT-bit set,
       J - Join SPT
Timers: Uptime/Expires
Interface state: Interface, State


!--- Here you see the mroute entry for the shared tree. Notice that the !--- incoming interface specifies outside and that the outgoing interface !--- list specifies inside.

(*, 224.1.2.3), 00:00:12/never, RP 172.16.1.2, flags: SCJ
  Incoming interface: outside
  RPF nbr: 172.16.1.2
  Outgoing interface list:
    inside, Forward, 00:00:12/never


!--- Here is the source specific tree for the mroute entry. 

(192.168.1.2, 224.1.2.3), 00:00:12/00:03:17, flags: SJ
  Incoming interface: outside
  RPF nbr: 0.0.0.0
  Immediate Outgoing interface list: Null

  • show conn—Displays the connection state for the designated connection type.

    
!--- A connection is built through the firewall for the multicast stream. !--- In this case the stream is sourced from the sender IP and destined !--- to the multicast group. 

ciscoasa#show conn
10 in use, 12 most used
UDP out 192.168.1.2:51882 in 224.1.2.3:1234 idle 0:00:00 flags -
ciscoasa#

  • show pim neighbor—Displays entries in the PIM neighbor table.

    
!--- When you use PIM, the neighbor devices should be seen with the !--- show pim neighbor command. 

ciscoasa#show pim neighbor

Neighbor Address  Interface          Uptime    Expires DR pri Bidir

172.16.1.2        outside            04:06:37  00:01:27 1 (DR)

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Troubleshooting Procedure

Follow these instructions in order to troubleshoot your configuration.

The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

Note: Refer to Important Information on Debug Commands before you use debug commands.

  1. If the multicast receivers are directly connected to the inside of the firewall, they send IGMP reports to receive the multicast stream. Use the show igmp traffic command in order to verify that you receive IGMP reports from the inside. 

    ciscoasa#show igmp traffic

IGMP Traffic Counters
Elapsed time since counters cleared: 04:11:08

                              Received     Sent
Valid IGMP Packets            413          244
Queries                       128          244
Reports                       159          0
Leaves                        0            0
Mtrace packets                0            0
DVMRP packets                 0            0
PIM packets                   126          0

Errors:
Malformed Packets             0
Martian source                0
Bad Checksums                 0

ciscoasa#

  2. The firewall can display more detailed information about the IGMP data by using the debug igmp command.

    In this case, the debugs are enabled and the host 10.0.0.2 sends an IGMP report for the group 224.1.2.3. 

    
!--- Enable IGMP debugging.

ciscoasa#debug igmp
IGMP debugging is on
ciscoasa# IGMP: Received v2 Report on inside from 10.0.0.2 for 224.1.2.3
IGMP: group_db: add new group 224.1.2.3 on inside
IGMP: MRIB updated (*,224.1.2.3) : Success
IGMP: Switching to EXCLUDE mode for 224.1.2.3 on inside
IGMP: Updating EXCLUDE group timer for 224.1.2.3

ciscoasa#

!--- Disable IGMP debugging

ciscoasa#un all

  3. Verify that the firewall has valid PIM neighbors and that the firewall sends and receives join/prune information. 

    ciscoasa#show pim neigh

Neighbor Address  Interface          Uptime    Expires DR pri Bidir

172.16.1.2        outside            04:26:58  00:01:20 1 (DR)

ciscoasa#show pim traffic

PIM Traffic Counters
Elapsed time since counters cleared: 04:27:11

                              Received     Sent
Valid PIM Packets             543          1144
Hello                         543          1079
Join-Prune                    0            65
Register                      0            0
Register Stop                 0            0
Assert                        0            0
Bidir DF Election             0            0

Errors:
Malformed Packets                           0
Bad Checksums                               0
Send Errors                                 0
Packet Sent on Loopback Errors              0
Packets Received on PIM-disabled Interface  0
Packets Received with Unknown PIM Version   0
Packets Received with Incorrect Addressing  0
ciscoasa#

  4. Use the capture command in order to verify that the outside interface receives the multicast packets for the group. 

    ciscoasa#configure terminal


!--- Create an access-list that is only used !--- to flag the packets to capture.

ciscoasa(config)#access-list captureacl permit ip any host 224.1.2.3


!--- Define the capture named capout, bind it to the outside interface, and !--- specify to only capture packets that match the access-list captureacl.

ciscoasa(config)#capture capout interface outside access-list captureacl


!--- Repeat for the inside interface.

ciscoasa(config)#capture capin interface inside access-list captureacl


!--- View the contents of the capture on the outside. This verifies that the !--- packets are seen on the outside interface

ciscoasa(config)#show capture capout
138 packets captured
   1: 02:38:07.639798 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   2: 02:38:07.696024 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   3: 02:38:07.752295 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   4: 02:38:07.808582 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   5: 02:38:07.864823 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   6: 02:38:07.921110 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   7: 02:38:07.977366 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   8: 02:38:08.033689 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   9: 02:38:08.089961 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  10: 02:38:08.146247 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  11: 02:38:08.202504 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  12: 02:38:08.258760 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  13: 02:38:08.315047 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  14: 02:38:08.371303 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  15: 02:38:08.427574 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  16: 02:38:08.483846 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  17: 02:38:08.540117 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  18: 02:38:08.596374 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  19: 02:38:08.652691 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  20: 02:38:08.708932 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  21: 02:38:08.765188 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  22: 02:38:08.821460 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  23: 02:38:08.877746 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  24: 02:38:08.934018 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316


!--- Here you see the packets forwarded out the inside !--- interface towards the clients.

ciscoasa(config)#show capture capin
89 packets captured
   1: 02:38:12.873123 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   2: 02:38:12.929380 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   3: 02:38:12.985621 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   4: 02:38:13.041898 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   5: 02:38:13.098169 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   6: 02:38:13.154471 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   7: 02:38:13.210743 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   8: 02:38:13.266999 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
   9: 02:38:13.323255 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  10: 02:38:13.379542 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  11: 02:38:13.435768 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  12: 02:38:13.492070 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  13: 02:38:13.548342 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  14: 02:38:13.604598 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  15: 02:38:13.660900 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  16: 02:38:13.717141 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  17: 02:38:13.773489 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  18: 02:38:13.829699 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  19: 02:38:13.885986 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  20: 02:38:13.942227 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  21: 02:38:13.998483 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  22: 02:38:14.054852 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  23: 02:38:14.111108 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
  24: 02:38:14.167365 192.168.1.2.52292 > 224.1.2.3.1234:  udp 1316
ciscoasa(config)#


!--- Remove the capture from the memory of the firewall.

ciscoasa(config)#no capture capout

Known Bugs

Cisco bug ID CSCse81633 (registered customers only) —ASA 4GE-SSM Gig ports silently drop IGMP joins.

  • Symptom—When a 4GE-SSM module is installed into an ASA and multicast-routing is configured along with IGMP on the interfaces, IGMP joins are dropped on the interfaces of the 4GE-SSM module.

  • Conditions—IGMP joins are not dropped on the onboard Gig interfaces of the ASA.

  • Workaround—For multicast routing, use the onboard Gig interface ports.

  • Fixed in versions—7.0(6), 7.1(2)18, 7.2(1)11

Related Information

Revision History

Revision Publish Date Comments
1.0
26-Sep-2008
Initial Release

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