Tuesday, 24 March 2015

show ip mroute Field Descriptions



Examples
The following is sample output from the show ip mroute command for a router operating in dense mode. This command displays the contents of the IP multicast routing table for the multicast group named cbone-audio.
Router# show ip mroute cbone-audio

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,
       Y - Joined MDT-data group, y - Sending to MDT-data group
Timers: Uptime/Expires
Interface state: Interface, Next-Hop, State/Mode

(*, 224.0.255.1), uptime 0:57:31, expires 0:02:59, RP is 224.0.0.0, flags: DC
  Incoming interface: Null, RPF neighbor 224.0.0.0, Dvmrp
  Outgoing interface list:
    Ethernet0, Forward/Dense, 0:57:31/0:02:52
    Tunnel0, Forward/Dense, 0:56:55/0:01:28

(192.168.37.100/32, 224.0.255.1), uptime 20:20:00, expires 0:02:55, flags: C
  Incoming interface: Tunnel0, RPF neighbor 10.20.37.33, Dvmrp
  Outgoing interface list:
    Ethernet0, Forward/Dense, 20:20:00/0:02:52

The following is sample output from the show ip mroute command for a router operating in sparse mode:
Router# show ip mroute

IP Multicast Routing Table
Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned
       R - RP-bit set, F - Register flag, T - SPT-bit set
Timers: Uptime/Expires
Interface state: Interface, Next-Hop, State/Mode

(*, 224.0.255.3), uptime 5:29:15, RP is 198.92.37.2, flags: SC
  Incoming interface: Tunnel0, RPF neighbor 10.3.35.1, Dvmrp
  Outgoing interface list:
    Ethernet0, Forward/Sparse, 5:29:15/0:02:57

(198.92.46.0/24, 224.0.255.3), uptime 5:29:15, expires 0:02:59, flags: C
  Incoming interface: Tunnel0, RPF neighbor 10.3.35.1
  Outgoing interface list:
    Ethernet0, Forward/Sparse, 5:29:15/0:02:57

The following is sample output from the show ip mroute command with the summary keyword:
Router# show ip mroute summary

IP Multicast Routing Table
Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned
       R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT
Timers: Uptime/Expires
Interface state: Interface, Next-Hop, State/Mode

(*, 224.255.255.255), 2d16h/00:02:30, RP 171.69.10.13, flags: SJPC

(*, 224.2.127.253), 00:58:18/00:02:00, RP 171.69.10.13, flags: SJC

(*, 224.1.127.255), 00:58:21/00:02:03, RP 171.69.10.13, flags: SJC

(*, 224.2.127.254), 2d16h/00:00:00, RP 171.69.10.13, flags: SJCL
  (128.9.160.67/32, 224.2.127.254), 00:02:46/00:00:12, flags: CLJT
  (129.48.244.217/32, 224.2.127.254), 00:02:15/00:00:40, flags: CLJT
  (130.207.8.33/32, 224.2.127.254), 00:00:25/00:02:32, flags: CLJT
  (131.243.2.62/32, 224.2.127.254), 00:00:51/00:02:03, flags: CLJT
  (140.173.8.3/32, 224.2.127.254), 00:00:26/00:02:33, flags: CLJT
  (171.69.60.189/32, 224.2.127.254), 00:03:47/00:00:46, flags: CLJT

The following is sample output from the show ip mroute command with the active keyword:
Router# show ip mroute active

Active IP Multicast Sources - sending >= 4 kbps

Group: 224.2.127.254, (sdr.cisco.com)
   Source: 146.137.28.69 (mbone.ipd.anl.gov)
     Rate: 1 pps/4 kbps(1sec), 4 kbps(last 1 secs), 4 kbps(life avg)

Group: 224.2.201.241, ACM 97
   Source: 130.129.52.160 (webcast3-e1.acm97.interop.net)
     Rate: 9 pps/93 kbps(1sec), 145 kbps(last 20 secs), 85 kbps(life avg)

Group: 224.2.207.215, ACM 97
   Source: 130.129.52.160 (webcast3-e1.acm97.interop.net)
     Rate: 3 pps/31 kbps(1sec), 63 kbps(last 19 secs), 65 kbps(life avg)

The following example of the show ip mroute EXEC command is displayed when IP multicast MLS is configured. Note that the "H" indicates hardware switched.
Router# show ip mroute

IP Multicast Routing Table
Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned
       R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT, H - Hardware
switched
Timers: Uptime/Expires

(*, 229.10.0.1), 00:04:35/00:02:59, RP 0.0.0.0, flags: DJC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
         Vlan6, Forward/Dense, 00:00:30/00:02:30
    Vlan5, Forward/Dense, 00:04:35/00:02:30
    Vlan2, Forward/Dense, 00:01:28/00:00:00

(192.0.2.20, 229.10.0.1), 00:04:35/00:02:27, flags: CT
Incoming interface: Vlan2, RPF nbr 0.0.0.0
Outgoing interface list:
    Vlan5, Forward/Dense, 00:03:25/00:00:00, H
    Vlan6, Forward/Dense, 00:00:10/00:00:00, H
Table  describes the significant fields shown in the output.
Table  show ip mroute Field Descriptions 
Field
Description
Flags:
Provides information about the entry.
 D - Dense
Entry is operating in dense mode.
 S - Sparse
Entry is operating in sparse mode.
 C - Connected
A member of the multicast group is present on the directly connected interface.
 L - Local
The router itself is a member of the multicast group.
 P - Pruned
Route has been pruned. The Cisco IOS software keeps this information in case a downstream member wants to join the source.
    R - RP-bit set
Indicates that the (S, G) entry is pointing toward the rendezvous point (RP). The RP is typically a prune state along the shared tree for a particular source.
    F - Register flag
Indicates that the software is registering for a multicast source.
    T - SPT-bit set 
Indicates that packets have been received on the shortest path source tree.
    H - Hardware switched
Indicates the outgoing interface is hardware switched because IP multicast MLS is enabled.
Timers:
Uptime/Expires.
Interface state:
Indicates the state of the incoming or outgoing interface.
http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifInterface. Indicates the type and number of the interface listed in the incoming or outgoing interface list.
http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifNext-Hop or VCD. "Next-hop" specifies the IP address of the downstream neighbor. "VCD" specifies the virtual circuit descriptor number. "VCD0" means the group is using the static map virtual circuit.
http://www.cisco.com/c/dam/en/us/td/i/templates/blank.gifState/Mode. "State" indicates that packets will either be forwarded, pruned, or null on the interface depending on whether there are restrictions due to access lists or a time-to-live (TTL) threshold. "Mode" indicates whether the interface is operating in dense, sparse, or sparse-dense mode
(*, 224.0.255.1)
(198.92.37.100/32, 224.0.255.1)
Entry in the IP multicast routing table. The entry consists of the IP address of the source router followed by the IP address of the multicast group. An asterisk (*) in place of the source router indicates all sources.
Entries in the first format are referred to as (*, G) or "star comma G" entries. Entries in the second format are referred to as (S, G) or "S comma G" entries. (*, G) entries are used to build (S, G) entries.
uptime
How long (in hours, minutes, and seconds) the entry has been in the IP multicast routing table.
expires
How long (in hours, minutes, and seconds) until the entry will be removed from the IP multicast routing table on the outgoing interface.
RP
Address of the rendezvous point router. For routers and access servers operating in sparse mode, this address is always 0.0.0.0.
flags:
Information about the entry.
Incoming interface:
Expected interface for a multicast packet from the source. If the packet is not received on this interface, it is discarded.
RPF neighbor
IP address of the upstream router to the source. "Tunneling" indicates that this router is sending data to the rendezvous point encapsulated in Register packets. The hexadecimal number in parentheses indicates to which rendezvous point it is registering. Each bit indicates a different rendezvous point if multiple rendezvous points per group are used.
Dvmrp or Mroute
Indicates whether the RPF information is obtained from the DVMRP routing table or the static mroutes configuration.
Outgoing interface list:
Interfaces through which packets will be forwarded. When the ip pim nbma-mode command is enabled on the interface, the IP address of the PIM neighbor is also displayed.
 Ethernet0
Name and number of the outgoing interface.
    Next hop or VCD
Next hop specifies the IP address of the downstream neighbors. VCD is the virtual circuit descriptor number. VCD0 means the group is using the static-map virtual circuit.
 Forward/Dense
Indicates that packets will be forwarded on the interface if there are no restrictions due to access lists or TTL threshold. Following the slash (/) is the mode in which the interface is operating (dense or sparse).
    Forward/Sparse
Sparse mode interface is in forward mode.
 <time/time>
    (uptime/expiration time)
Per interface, how long (in hours, minutes, and seconds) the entry has been in the IP multicast routing table. Following the slash (/) is how long (in hours, minutes, and seconds) until the entry will be removed from the IP multicast routing table.

MLD (multicast listener discovery) snooping

Introduction:

In IPv4 multicast group membership is managed through Internet Group Management Protocol (IGMP).Internet Group Management Protocol (IGMP) is a protocol that manages host membership in IP multicast group. A specific host listens on a specific IP multicast address and receives all packets to that IP address. In IPv6, multicast group management is accomplished with a set of ICMPv6 messages that comprise the Multicast Listener Discovery (MLD) protocol.

MLD Basic Overview:

MLDv1 is similar to IGMPv2 and MLDv2 similar to IGMPv3.Like IGMP, MLDv2 is backward compatible to MLDv1.For cisco switches, MLD snooping provides the same functionality as IGMP snooping in IPv4.It provides information to the switch about which connected hosts are member of a specific group so that switch can make decision about whether, and on which interface, to allow traffic for that group.

MLD is automatically enabled when you perform one of the following configuration tasks on an interface:
•Enable PIM6
•Statically bind a local multicast group
•Enable link-local group reports

MLD uses three different types of messages:
1) Multicast Listener Query: The Query message type has two subtypes.
->The General Query issued by routers to discover the entire multicast groups that listeners on the link are subscribed to.
-> Multicast-Address-Specific Query: issued by routers to discover whether there are any local link subscribers (listeners) to a particular multicast address. Only routers send queries, and usually there is only one router that acts as a querier on each link.
2) Multicast Listener Report: An unsolicited Report message is sent by any node when it begins listening to a multicast address; Report messages are generated in response to a Query message sent by a router(either a query for a specific multicast address or a general query).
3) Multicast Done: In a done message, the multicast address field is that of the specific IPv6 multicast address to which the source of the MLD message is no longer listening.

The figure below shows where MLD operate within the IPv6 multicast environment.
1

Configuration Overview:


A) Configuring MLD Snooping:

To enable MLD snooping globally, perform this task:
Router(config)# ipv6 mld snooping
Router(config)# end
Router# show ipv6 mld interface vlan 100 | include globally
  MLD snooping is globally enabled
Router#

To enable MLD snooping in a VLAN, perform this task:

Router# interface vlan 125
Router(config-if)# ipv6 mld snooping
Router(config-if)# end
Router# show ipv6 mld interface vlan 125 | include snooping
  MLD snooping is globally enabled
  MLD snooping is enabled on this interface
  MLD snooping fast-leave is enabled and querier is enabled
  MLD snooping explicit-tracking is enabled
  MLD snooping last member query response interval is 1000 ms
  MLD snooping report-suppression is disabled
Router#

B) Configures MLD reporting for a specified group and source.
Router(config)#int fa0/0
Router(config-if)# ipv6 mld join-group FF04::12 exclude 2001::1

C) To allow the user to perform IPv6 multicast receiver access control:  
Router(config)#int fa0/0
Router(config-if)# ipv6 access-list (Acl_Name)

D) To statically forward traffic for the multicast group onto a specified interface and cause the interface to behave as if a MLD joiner were present on the interface.
Router(config)#int fa0/0
Router(config-if)# ipv6 mld static-group ff04::10 include 100::1

E) Configures the maximum response time advertised in MLD queries.
Router(config)#int fa0/0
Router(config-if)# ipv6 mld query-max-response-time 20

F) Configures the timeout value before the device takes over as the querier for the interface.
Router(config)#int fa0/0
Router(config-if)# ipv6 mld query-timeout 130  

G) Configures the frequency to sends MLD host-query messages.  
Router(config)#int fa0/0
Router(config-if)# ipv6 mld query-interval 60

H)Verification Command:

-> To displays multicast-related information about an interface
Router#show ipv6 mld interface fa0/0

-> To displays the multicast groups that are directly connected to the device and that were learned through MLD.
Router#Show ipv6 mld groups

J) To reset the MLD :
Router#clear ipv6 mld ?
  counters  Clear interface counters
  group     Delete group cache entries
  traffic   Clear traffic counters

Reference:

Multicast Listener Discovery Version 2 (MLDv2) for IPv6
Configuring MLD