RE: Multicast issue in NBMA

Ping 255.255.255.255 from one of the spokes. Who responds?

Brian McGahan, CCIE #8593 (R&S/SP/Security), CCDE #2013::13
bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>

Internetwork Expert, Inc.
http://www.INE.com<http://www.ine.com/>

From: Taio Bone [mailto:taiobtnh_at_gmail.com]
Sent: Thursday, July 04, 2013 3:10 PM
To: Brian McGahan
Cc: Tony Singh; Cisco certification
Subject: Re: Multicast issue in NBMA

Thanks Brian for this: "and since you can't route link-local multicast"...All
my assumption was both spokes are in the same broadcast domain(and I have the
"broadcast" keyword with the frame map command) even with the each spoke
having a next-hop as the other spoke...That was the concept/fact I was
forgetting....And yes,using a point-to-multipoint does work as well as the
Tunnel as suggested by Tony.
Thanks everone.

On Thu, Jul 4, 2013 at 8:58 PM, Brian McGahan
<bmcgahan_at_ine.com<mailto:bmcgahan_at_ine.com>> wrote:
The issue is like you said, the join for the RPF neighbor is for someone who
can't be reached by the spoke. Even though the PIM join is a multicast, there
is an encoded unicast address in the JOIN packet. The result is that the hub
will drop the packet since it's not the destination and since you can't route
link-local multicast. The solution for this is to change to OSPF
point-to-multipoint where the hub will be the next-hop, and hence the encoded
unicast address in the multicast join will be the connected neighbor, or like
Tony said to use a GRE tunnel.

In reality both of these solutions are a hack. The correct design solution is
to only use p2p IP subnets and p2p subinterfaces for NBMA, which remove tons
of design problems such as this with multicast. Of course within the scope of
the CCIE lab exam you have to deal with their restrictions. So theoretically
if they were to say that you have to use OSPF broadcast network type and you
can't use P2P subinterfaces and the sender and receiver are on different
spokes then you'd have to tunnel the traffic. If the sender/receiver is
behind the hub and the sender/receiver is behind the spoke then it's fine,
it's only a spoke to spoke issue.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security), CCDE #2013::13
bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>

Internetwork Expert, Inc.
http://www.INE.com

-----Original Message-----
From: nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>
[mailto:nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>] On Behalf Of Taio
Bone
Sent: Thursday, July 04, 2013 2:52 PM
To: Tony Singh
Cc: Cisco certification
Subject: Re: Multicast issue in NBMA

Also ALL routers are 7200 series

R2(config)#do sh ver
Cisco IOS Software, 7200 Software (C7200-IK9O3S-M), Version 12.4(12c), RELEASE
SOFTWARE (fc1) Technical Support: http://www.cisco.com/techsupport Copyright
(c) 1986-2007 by Cisco Systems, Inc.
Compiled Fri 13-Jul-07 09:55 by prod_rel_team

On Thu, Jul 4, 2013 at 8:49 PM, Taio Bone
<taiobtnh_at_gmail.com<mailto:taiobtnh_at_gmail.com>> wrote:

> R1
>
> FRS
>
> R2 R3
> f0/0 f0/0
> | |
> | |
> f0/0 f0/0
> R4 R5
> *
> *
> **R3 is the RP and are statically configure on ALL routers including
> the RP itself*
>
> **Igmp join is being sent from R4's f0/0 interface....R2 receives the
> join message and has the (*,G) entry for the group*
>
> R2(config)#
> PIM(0): Check RP 3.3.3.3 into the (*, 224.6.6.6) entry
> PIM(0): Received v2 Join/Prune on FastEthernet0/0 from 24.24.24.4, to
> us
> PIM(0): Join-list: (*, 224.6.6.6), RPT-bit set, WC-bit set, S-bit set
> PIM(0): Add FastEthernet0/0/24.24.24.4<http://24.24.24.4> to (*, 224.6.6.6),
Forward
> state, by PIM *G Join
> PIM(0): Building Triggered (*,G) Join / (S,G,RP-bit) Prune message for
> 224.6.6.6
> R2(config)#
>
> R2(config)#do sh ip mroute 224.6.6.6
> 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
>
> (*, 224.6.6.6), 00:01:11/00:03:16, RP 3.3.3.3, flags: SJC
> Incoming interface: Serial1/0, RPF nbr 10.10.10.3
> Outgoing interface list:
> FastEthernet0/0, Forward/Sparse, 00:01:11/00:03:16
>
>
> *
> *
> **the multicast source is being sent from R5's f0/0 interface,hence
> the DR is R3 which happens to be the RP as well as evident by the
> below output
> *
>
>
> R3(config)#do sh log
> Syslog logging: enabled (12 messages dropped, 1 messages rate-limited,
> 0 flushes, 0 overruns, xml disabled, filtering disabled)
> Console logging: level alerts, 150 messages logged, xml disabled,
> filtering disabled
> Monitor logging: level debugging, 0 messages logged, xml disabled,
> filtering disabled
> Buffer logging: level debugging, 165 messages logged, xml disabled,
> filtering disabled
> Logging Exception size (8192 bytes)
> Count and timestamp logging messages: disabled
>
> No active filter modules.
>
> Trap logging: level informational, 62 message lines logged
>
> Log Buffer (8192 bytes):
>
> PIM(0): Received v2 Join/Prune on FastEthernet0/0 from 35.35.35.5, to
> us
> PIM(0): Join-list: (*, 224.0.1.40), RPT-bit set, WC-bit set, S-bit set
> PIM(0): Update FastEthernet0/0/35.35.35.5<http://35.35.35.5> to (*,
224.0.1.40), Forward
> state, by PIM *G Join
> PIM(0): v1, bad checksum from 35.35.35.5 (FastEthernet0/0)
> PIM(0): Check RP 3.3.3.3 into the (*, 224.2.2.2) entry
> PIM(0): Received v2 Register on FastEthernet0/0 from 35.35.35.5
> for 35.35.35.5, group 224.2.2.2
> PIM(0): Send v2 Register-Stop to 35.35.35.5 for 35.35.35.5, group
> 224.2.2.2
> PIM(0): Received v2 Register on FastEthernet0/0 from 35.35.35.5
> for 5.5.5.5, group 224.2.2.2
> PIM(0): Send v2 Register-Stop to 35.35.35.5 for 5.5.5.5, group
> 224.2.2.2
> PIM(0): v1, bad checksum from 35.35.35.5 (FastEthernet0/0)
> PIM(0): Building Periodic (*,G) Join / (S,G,RP-bit) Prune message for
> 224.0.1.40
> PIM(0): Building Periodic (*,G) Join / (S,G,RP-bit) Prune message for
> 224.1.1.1
> PIM(0): Received v2 Join/Prune on FastEthernet0/0 from 35.35.35.5, to
> us
> PIM(0): Join-list: (*, 224.0.1.40), RPT-bit set, WC-bit set, S-bit set
> PIM(0): Update FastEthernet0/0/35.35.35.5<http://35.35.35.5> to (*,
224.0.1.40), Forward
> state, by PIM *G Join
> PIM(0): Send RP-reachability for 224.0.1.40 on FastEthernet0/0
> PIM(0): Send RP-reachability for 224.0.1.40 on Serial1/0
> PIM(0): Building Periodic (*,G) Join / (S,G,RP-bit) Prune message for
> 224.2.2.2
> PIM(0): Received v2 Register on FastEthernet0/0 from 35.35.35.5
> PIM(0): Send v2 Register-Stop to 35.35.35.5 for 0.0.0.0, group 0.0.0.0
>
>
>
> **R1 is neither receiving the join message nor does it have an entry
> for the (*,G)*
>
> R1(config-if)#do sh ip mroute 224.6.6.6 Group 224.6.6.6 not found
>
>
> *MORE OUTPUT*
>
> R2(config)#do sh frame map
> Serial1/0 (up): ip 10.10.10.1 dlci 201(0xC9,0x3090), static,
> broadcast,
> CISCO, status defined, active
> Serial1/0 (up): ip 10.10.10.2 dlci 201(0xC9,0x3090), static,
> CISCO, status defined, active
> Serial1/0 (up): ip 10.10.10.3 dlci 201(0xC9,0x3090), static,
> CISCO, status defined, active
>
>
> R3(config)#do sh frame map
> Serial1/0 (up): ip 10.10.10.1 dlci 301(0x12D,0x48D0), static,
> broadcast,
> CISCO, status defined, active
> Serial1/0 (up): ip 10.10.10.2 dlci 301(0x12D,0x48D0), static,
> CISCO, status defined, active
>
>
> R2(config)#do sh ip route
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
> ia - IS-IS inter area, * - candidate default, U - per-user static
> route
> o - ODR, P - periodic downloaded static route
>
> Gateway of last resort is not set
>
> 1.0.0.0/32<http://1.0.0.0/32> is subnetted, 1 subnets
> O 1.1.1.1 [110/65] via 10.10.10.1, 00:37:27, Serial1/0
> 35.0.0.0/24<http://35.0.0.0/24> is subnetted, 1 subnets
> O 35.35.35.0 [110/65] via 10.10.10.3, 00:37:27, Serial1/0
> 2.0.0.0/32<http://2.0.0.0/32> is subnetted, 1 subnets
> C 2.2.2.2 is directly connected, Loopback1
> 3.0.0.0/32<http://3.0.0.0/32> is subnetted, 1 subnets
> O 3.3.3.3 [110/65] via 10.10.10.3, 00:37:27, Serial1/0
> 4.0.0.0/32<http://4.0.0.0/32> is subnetted, 1 subnets
> O 4.4.4.4 [110/2] via 24.24.24.4, 00:37:27, FastEthernet0/0
> 5.0.0.0/32<http://5.0.0.0/32> is subnetted, 1 subnets
> O 5.5.5.5 [110/66] via 10.10.10.3, 00:37:27, Serial1/0
> 24.0.0.0/24<http://24.0.0.0/24> is subnetted, 1 subnets
> C 24.24.24.0 is directly connected, FastEthernet0/0
> 10.0.0.0/24<http://10.0.0.0/24> is subnetted, 1 subnets
> C 10.10.10.0 is directly connected, Serial1/0
>
>
>
>
>
>
> R3(config)#do sh ip route
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
> ia - IS-IS inter area, * - candidate default, U - per-user static
> route
> o - ODR, P - periodic downloaded static route
>
> Gateway of last resort is not set
>
> 1.0.0.0/32<http://1.0.0.0/32> is subnetted, 1 subnets
> O 1.1.1.1 [110/65] via 10.10.10.1, 00:36:54, Serial1/0
> 35.0.0.0/24<http://35.0.0.0/24> is subnetted, 1 subnets
> C 35.35.35.0 is directly connected, FastEthernet0/0
> 2.0.0.0/32<http://2.0.0.0/32> is subnetted, 1 subnets
> O 2.2.2.2 [110/65] via 10.10.10.2, 00:36:54, Serial1/0
> 3.0.0.0/32<http://3.0.0.0/32> is subnetted, 1 subnets
> C 3.3.3.3 is directly connected, Loopback1
> 4.0.0.0/32<http://4.0.0.0/32> is subnetted, 1 subnets
> O 4.4.4.4 [110/66] via 10.10.10.2, 00:36:54, Serial1/0
> 5.0.0.0/32<http://5.0.0.0/32> is subnetted, 1 subnets
> O 5.5.5.5 [110/2] via 35.35.35.5, 00:36:54, FastEthernet0/0
> 24.0.0.0/24<http://24.0.0.0/24> is subnetted, 1 subnets
> O 24.24.24.0 [110/65] via 10.10.10.2, 00:36:54, Serial1/0
> 10.0.0.0/24<http://10.0.0.0/24> is subnetted, 1 subnets
> C 10.10.10.0 is directly connected, Serial1/0
>
>
>
>
>

--
Warm wishes,
Ty.
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