Michael McNamara

technology, networking, virtualization and IP telephony

IST Instability in large Multicast networks

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Avaya has released a technical support bulletin detailing an issue that can impact IST stability in a large Multicast network. I know a number of readers have had issues with Multicast support in extremely large networks.

In large campus networks with SMLT topologies where multicast routing protocols (such as PIM) have been provisioned and scaled to large amounts of multicast senders and receivers, it has been observed that high CPU utilization
(sometimes combined with high CPU buffer utilization) leading to IST instability may occur during re-convergence of the multicast routing protocols after failures.

Additional information;

Release 5.1.3.0 has been modified with changes that were originally introduced in release 7.0.0.0. These changes allow IST protocol messages to be processed even under high CPU utilization. This is achieved by checking to see if IST control messages are queued up (but not yet processed) before deciding that the IST session has timed out and needs to be brought down. Each line card recognizes and counts IST control messages when they arrive and before they are sent to the CP, and the IST message processing logic on the CP will check for outstanding IST control messages before deciding the IST needs to be brought down due to inactivity.

Cheers!

Multicast Routing Protocol (Part 2)

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In part 1 of this post I looked at how to configure DVMRP to facilitate inter-VLAN Multicast commuications on a single switch. In this post I’ll look at how to configure PIM to facilitate inter-VLAN Multicast communications across multiple switches and routers (Layer 3 switches).

I took a few minutes and threw together a quick diagram to help layout the topology (a picture is truly worth a thousand words). There are two core ERS 8600 switches (a switch cluster as Nortel likes to call it these days). There are three VLANs bridged across all four switches in the diagram, VLAN 55, 56 and 200. There is a fourth VLAN, 57, that is routed from ERS 8600 C. The ERS 5520 in the diagram will only be used as a Layer 2 even though it could potentially be used as a Layer 3 device (router).


I’m going to review two possible configurations. The first scenario will be for a client device (VLC Client A) in a VLAN routed by the core ERS 8600s. The second scenario will be for a client device (VLC Client B) in a VLAN routed by a closet ERS 8600.

Lets get on with configuring some ERS 8600 switches. First lets enable PIM globally;

ERS8600-A# config ip pim enable
ERS8600-A# config ip pim fast-joinprune enable

Then we’ll enable PIM on the specific VLANs;

ERS8600-A# config vlan 55 ip pim enable
ERS8600-A# config vlan 56 ip pim enable
ERS8600-A# config vlan 200 ip pim enable

We need to create a CLIP interface to use for PIM routing, we don’t want to tie the PIM routing to a physical interface in case that interface goes down for whatever reason. We’re already using CLIP 1 for our OSPF router ID of 10.1.0.5/32.

ERS8600-A# config ip circuitless-ip-int 2 create 10.1.0.15/255.255.255.255
ERS8600-A# config ip circuitless-ip-int 2 ospf enable
ERS8600-A# config ip circuitless-ip-int 2 pim enable

We need to add a candidate Rendezvous Point Router (RP) pointing it to our CLIP address.

ERS8600-A# ip pim candrp add grp 239.255.1.1 mask 255.255.255.255 rp 10.1.0.15

We need to set the priority of the Bootstrap Router (BSR) for dynamic PIM routing.

ERS8600-A# ip pim interface 10.1.0.15 cbsrpreference 100

Then on the second core ERS 8600 switch;

ERS8600-B# config ip pim enable
ERS8600-B# config ip pim fast-joinprune enable
ERS8600-B# config vlan 55 ip pim enable
ERS8600-B# config vlan 56 ip pim enable
ERS8600-B# config vlan 200 ip pim enable
ERS8600-B# config ip circuitless-ip-int 2 create 10.1.0.16/255.255.255.255
ERS8600-B# config ip circuitless-ip-int 2 ospf enable
ERS8600-B# config ip circuitless-ip-int 2 pim enable
ERS8600-B# config ip pim candrp add grp 239.255.1.1 mask 255.255.255.255 rp 10.1.0.16
ERS8600-B# config ip pim interface 10.1.0.16 cbsrpreference 50

That’s really all there is to configure with the two core ERS 8600 switches.

ERS5520 Switch (Edge)
In the case of the ERS 5520 switch there really isn’t anything you need to configure per say. You could enable IGMP (generally disabled by default) to filter the multicast traffic from ports that are not subscribing to any multicast groups. Since the ERS8600s are performing the routing the ERS5520 acts just like a Layer 2 switch.

VLC Client A (10.1.56.50) should now be able to connect to the multicast group 239.255.1.1 from the ERS 5520 which will be sourced from the VLC Server (10.1.55.50).

ERS8600 C Switch (Edge)
In the case of the ERS 8600 switch (edge) you need to configure and enable PIM. We’ll using VLAN 200 to interface with the upstream ERS8600 switches

ERS8600-C:5# config ip pim enable
ERS8600-C:5# config vlan 57 ip pim enable
ERS8600-C:5# config vlan 57 ip pim interface-type passive
ERS8600-C:5# config vlan 200 ip pim enable

Since there won’t be any other Layer 3 PIM switches on VLAN 57 we set the PIM interface to passive (much like the OSPF equivalent of passive).

VLC Client B (10.1.57.50) should now be able to connect to the multicast group 239.255.1.1 from the ERS 8600 C which will be sourced from the VLC Server (10.1.55.50).

We can dump the multicast (PIM) routing table with the following command from the edge ERS8600 switch;

ERS8600-C:5# show ip pim mroute

================================================================================
Pim Multicast Route
================================================================================
Src: 0.0.0.0 Grp: 230.0.0.2 RP: 10.1.0.5 Upstream: 10.1.200.5
Flags: WC RP CACHE
Incoming Port: Vlan200-1/1,
Outgoing Ports: Vlan127-2/42,
Joined Ports:
Pruned Ports:
Leaf Ports: Vlan127-2/42,
Asserted Ports:
Prune Pending Ports:
Assert Winner Ifs:
Assert Loser Ifs:
TIMERS:
Entry JP RS Assert
151 1 0 0
VLAN-Id: 200
Join-P: 0
Assert: 0
——————————————————————————–
Src: 10.1.233.30 Grp: 230.0.0.2 RP: 10.1.0.5 Upstream: 10.1.200.5
Flags:
SPT CACHE SG
Incoming Port: Vlan200-1/1,
Outgoing Ports: Vlan127-2/42,
Joined Ports:
Pruned Ports:
Leaf Ports: Vlan127-2/42,
Asserted Ports:
Prune Pending Ports:
Assert Winner Ifs:
Assert Loser Ifs:
TIMERS:
Entry JP RS Assert
64 4 0 0
VLAN-Id: 200
Join-P: 0
Assert: 0
——————————————————————————–

Total Num of Entries Displayed 2
Flags Legend:
SPT = Shortest path tree, WC=(*,Grp) entry, RP=Rendezvous Point tree, CACHE=Kernel Cache, ASSERTED=Asserted, SG=(Src,Grp) entry, PMBR=(*,*,RP) entry, FWD_TO_RP=Forwarding to RP, FWD_TO_DR=Forwarding to DR, SG_NODATA=SG Due to Join, CP_TO_CPU=Copy to CPU, STATIC_MROUTE=Static Mroute, MRTF_SMLT_PEER_SG=Peer SG On Non-DR For SMLT
——————————————————————————–

Troubleshooting

Here are some basic commands that should help you troubleshoot any PIM issues;

ERS8600-A:5# show ip pim neighbor

================================================================================
Pim Neighbor
================================================================================
INTERFACE ADDRESS UPTIME EXPIRE
——————————————————————————–
Vlan55 10.1.55.6 31 day(s), 00:09:53 0 day(s), 00:01:40
Vlan56 10.1.56.6 31 day(s), 00:09:53 0 day(s), 00:01:40
Vlan200 10.1.200.6 31 day(s), 00:09:53 0 day(s), 00:01:34

Total PIM Neighbors = 3

We can see that all three VLAN interfaces have PIM neighbors with the ERS 8600 B switch. Lets just check the RPs and make sure we have the correct multicast groups (addresses).

ERS8600-A:5# show ip pim rp-set

================================================================================
Pim RPSet
================================================================================
GRPADDRESS GRPMASK ADDRESS HOLDTIME EXPTIME
——————————————————————————–
230.0.0.1 255.255.255.255 10.1.0.15 150 137
230.0.0.2 255.255.255.255 10.1.0.15 150 137
239.255.1.1 255.255.255.255 10.1.0.15 150 137

The multicast addresses of 230.0.0.1 and 230.0.0.2 listed above are used for Nortel’s Contact Center (formerly Symposium Call Center software). Here’s how we can list the candidate RPs;

ERS8600-A:5# show ip pim candidate-rp

================================================================================
Pim Candidate RP Table
================================================================================
GRPADDR GRPMASK RPADDR
——————————————————————————–
230.0.0.1 255.255.255.255 10.1.0.15
230.0.0.2 255.255.255.255 10.1.0.15
239.255.1.1 255.255.255.255 10.1.0.15

If we’re dynamically choosing a RP we need to make sure that there is a BSR active;

ERS8600-A:5# show ip pim bsr

================================================================================
Current BootStrap Router Info
================================================================================

Current BSR address: 10.1.0.15
Current BSR priority: 100
Current BSR HashMask: 255.255.255.252
Current BSR Fragment Tag: 44590
Pim Bootstrap Timer : 31

I may need to update this article to make it cleaner and clearer.

Cheers!

Multicast Routing Protocol (Part 1)

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I was originally just going to write about DVMRP, but I’ve also decided to post some basic examples for setting up PIM-SM. I’ll break this post into two parts; first part will look at utilizing DVMRP to setup a simple Multicast domain on a single switch while the second part will look at utilizing PIM-SM across multiple switches.

We have a few Nortel Contact Center (formerly Symposium) installations deployed throughout the organization. The Nortel Agent Desktop Display (ADD) utilizes multicast to distribute the information between the server and the individual clients. Unless the clients are in the same VLAN as the server (Application/Web server and Database server) you’re going to need a Multicast Routing Protocol to facilitate the multicast communications between VLANs. I should point out that at this point I’m only talking about making multicast traffic available between VLANs on a single Nortel Ethernet Routing Switch 8600.

Note: Nortel Contact Center 6.0 appears to use the following two Multicast addresses by default; 230.0.0.1, 230.0.0.2

Unfortunately I didn’t have a spare Contact Center server to test with so I needed to figure out how I could test multicast traffic ahead of time and then just schedule any changes that needed to be made to facilitate inter-VLAN multicast communications. I recalled that VideoLAN – VLC media player could stream audio/video via multicast.

In order to test I setup two laptops running Windows XP Service Pack 2, laptop A (10.1.55.50/24) on VLAN 55 (10.1.55.0/24) and laptop B (10.1.56.50/24) on VLAN 56 (10.1.56.0/24).

Laptop A will be the broadcast server and stream the video while laptop B will be the client.

Let’s setup the ERS 8600 switch;

ERS-8610:6# config vlan 55 create byport 1
ERS-8610:6# config vlan 55 ip address 10.1.55.5/24
ERS-8610:6# config vlan 55 ip ospf enable
ERS-8610:6# config vlan 55 ip vrrp 1 10.1.55.1
ERS-8610:6# config vlan 55 ip dvmrp enable
ERS-8610:6# config vlan 56 create byport 1
ERS-8610:6# config vlan 56 ip address 10.1.56.5/24
ERS-8610:6# config vlan 56 ip ospf enable
ERS-8610:6# config vlan 56 ip vrrp 1 10.1.56.1
ERS-8610:6# config vlan 56 ip dvmrp enable

And then some global settings;

ERS-8610:6# config ip dvmrp enable
ERS-8610:6# config ip ospf enable

Now we need to look at how to make VLC do what we need;

Once you install VLC and start the program you will be greeted by this lightweight frontend.

Click File -> Open File to bring up the Open dialog box.

Click on the Browse button to bring up a standard Windows file selection box. Select the file you want to play. Then click Open.

Your selection should appear in the text box next to the Browse button. Click the check box for Stream Output and then click the button Settings.

If you wish to view the video on the source laptop then check the box next to Play Locally under Output Methods. When streaming to another system you don’t have to play the file on the server, but you can use this option to visually confirm that our video is playing properly before trying to access the stream from another computer.

Check the box marked UDP and type in the Muticast address you want to stream the file to. You should use a local-scope multicast address between 239.0.0.0 – 239.255.255.255. You should also make sure that the Time-To-Live (TTL) is set to 2. Then click OK. The file is ready to play so click OK in the Open dialog box too.

The video or audio file should begin playing on the computer. The last thing to do before switching to the second laptop is to turn on VLC’s web interface by clicking Settings -> Add Interface -> Web Interface. This will help provide remote control over VLC if we should need it from the second laptop.

Open VLC on the second laptop.

Click on File -> Open Network Stream. Select UDP/RTP Multicast and use the same Multicast address you use on the server. Click the OK button and VLC will start playing your stream.

Now that the stream is successfully playing on your computer you can open up a web browser to control VLC remotely. Type http://10.1.55.10:8080/ into the address bar. The web browser will present you with all of the controls you need to manage playlists and playback remotely.

If you’ve setup the ERS8600 properly your video should start playing on the client laptop.

If you want to make sure that VLC is configured and working properly move both laptops to the same VLAN. If the video stream works then you know that VLC is working properly and you need to focus the network configuration.

Note: Windows XP defaults to IGMP v3 which is fine for this test.

You can use the following commands to troubleshoot the network pieces. In the examples below I had the laptops connected to an ERS 5520 switch which was uplink on port 1/1. That is why the port is reported as 1/1 throughout the different commands.

DVMRP

ERS-8610:6# show ip dvmrp info
==================================================================                        Dvmrp General Group
==================================================================

AdminStat               : enabled
Genid                   : 0x47c42ef1
Version                 : 3
NumRoutes               : 2
NumReachableRoutes      : 2

UpdateInterval          : 60
TriggeredUpdateInterval : 5
LeafTimeOut             : 125
NbrTimeOut              : 35
NbrProbeInterval        : 10
FwdCacheTimeout         : 300
RouteExpireTimeout      : 140
RouteDiscardTimeout     : 260
RouteSwitchTimeout      : 140
ShowNextHopTable        : disable
generate-trap            : disable
generate-log             : disable
PruneResend             : disable

ERS-8610:6# show ip dvmrp interface

================================================================================                        Dvmrp Interface
================================================================================                                         DEFAULT DEFAULT DEFAULT ADVERTISEIF        ADDR            METRIC OPERSTAT LISTEN  SUPPLY  METRIC  SELF
-------------------------------------------------------------------------------
Vlan55    10.1.55.1       1      up       enable  disable 1       enable
Vlan56    10.1.56.1       1      up       enable  disable 1       enable

2 out of 2 entries displayed

--------------------------------------------------------------------------------
IF        ADDR            IN-POLICY       OUT-POLICY      INTF TYPE
--------------------------------------------------------------------------------
Vlan55    10.1.55.1                                      ActiveVlan56    10.1.56.1                                      Active

2 out of 2 entries displayed

ERS-8610:6# show ip dvmrp route

================================================================================
                       Dvmrp Route
================================================================================
SOURCE          MASK            UPSTREAM_NBR    INTERFACE  METRIC EXPIRE
--------------------------------------------------------------------------------
10.107.55.0     255.255.255.0   0.0.0.0         Vlan55     1      155
10.107.56.0     255.255.255.0   0.0.0.0         Vlan56     1      155

2 out of 2 entries displayed

IGMP 

ERS-8610:6# show ip igmp cache
================================================================================
                        Igmp Cache
================================================================================
GRPADDR         INTERFACE  LASTREPORTER    EXPIRATION V1HOSTTIMER  TYPE       STATICPORTS
--------------------------------------------------------------------------------
239.255.1.1     Vlan56     10.1.56.50    213        0            DYNAMIC NULL
239.255.255.250 Vlan55     10.1.55.50    214        0            DYNAMIC NULL
239.255.255.250 Vlan56     10.1.56.50    219        0            DYNAMIC NULL

3 out of 3 entries displayed

ERS-8610:6# show ip igmp group

================================================================================
                        Igmp Group
================================================================================
GRPADDR         INPORT          MEMBER          EXPIRATION TYPE
-------------------------------------------------------------------------------
239.255.1.1     V56-1/1         10.1.56.50      209        Dynamic
239.255.255.250 V55-1/1         10.1.55.50      210        Dynamic
239.255.255.250 V56-1/1         10.1.56.50      215        Dynamic

Total number of groups 3Total number of unique groups 2

ERS-8610:6# show ip igmp sender

================================================================================
                        Igmp Sender
===============================================================================
GRPADDR         IFINDEX    MEMBER          PORT       STATE
--------------------------------------------------------------------------------
239.255.1.1     Vlan 55    10.1.55.50      1/1        NOTFILTERED

1 out of 1 entries displayed

Hopefully I haven’t gone over the top on this one.

Please post any comments, corrections or suggestions.

Cheers!

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