README

pimd is a lightweight, stand-alone implementation of RFC 2362, available under the 3-clause BSD license. This is the restored original version from University of Southern California, by Ahmed Helmy, Rusty Eddy and Pavlin Ivanov Radoslavov.

pimd is maintained at GitHub. Use its facilities to access the source, report bugs, feature requests, send patches and for GIT pull requests:

http://github.com/troglobit/pimd

pimd also has a homepage, mainly to distribute releases:

http://troglobit.com/pimd.html

pimd is primarily developed on Linux and should work as-is out of the box on all major distributions. Other UNIX variants should also work, but are not as thoroughly tested. For some tips and details, see the configure script.

Building

When building pimd from source you first need to run the configure script to generate the file config.mk. The script relies on Bourne shell standard features as well as expr and uname. Any optional pimd features, such as --enable-scoped-acls are activated here as well.

Example:

./configure --enable-scoped-acls
make

sudo make install

The Makefile supports de facto standard environment variables such as prefix and DESTDIR for the install process. E.g., to install pimd to /usr instead of the default /usr/local, but redirect to a binary package directory in /tmp:

VERSION=2.2.0-1 prefix=/usr DESTDIR=/tmp/pimd-2.2.0-1 make clean install

Configuration

The configuration is kept in the file /etc/pimd.conf, the order of the statements are in some cases important.

PIM-SM is a designed to be a protocol independent multicast routing protocol. As such it relies on protocols like, e.g, OSPF, RIP, or static routing entries, to figure out the path to all multicast capable neighboring routers. This information is necessary in setups with more than one route between a multicast sender and a receiver to figure out which PIM router should be the active forwarder.

However, pimd currently cannot retrieve the unicast routing distance (preference) and metric of routes from the system, not from the kernel nor a route manager like zebra. Hence, pimd currently needs to be setup statically on each router using the desired distance and metric for each active interface. If either the distance and/or the metric is missing in an interface configuration, the following two defaults will be used:

default_source_preference <1-255>     default: 101   (distance)
default_source_metric     <1-1024>    default: 1024

By default pimd starts up on all interfaces it can find, using the above defaults. To configure individual interfaces use:

phyint <address | ifname> ...

You can reference the interface via either its local IPv4 address or its name, e.g., eth0. Some common interface settings are:

• disable: Disable pimd on this interface, i.e., do not send or listen for PIM-SM traffic

• preference <1-255>: The interface's distance value (also confusingly referred to as metric preference) in PIM Assert messages. Used with metric to elect the active multicast forwarding router. Defaults to default_source_preference

• metric <1-1024>: The cost for traversing this router. Used with the preference value above. Defaults to default_source_metric

More interface settings are available, see the pimd(8) manual page for the full details.

The most notable feature of PIM-SM is that multicast is distributed from so called Rendezvous Points (RP). Each RP handles distribution of one or more multicast groups, pimd can be configured to advertise itself as a candidate RP cand_rp, and request to be static RP rp_address for one or more multicast groups.

rp_address <address> [<group>[/<LENGTH> | masklen <LENGTH]

The rp_address setting is the same as the Cisco ip pim rp-address setting to configure static Rendezvous Points. The first argument can be an IPv4 address or a multicast group address. The default group and prefix length is 224.0.0.0/16. Static RP's always have priority 1.

cand_rp [address | ifname] [time <10-16383>] [priority <0-255>]

The Rendezvous Point candidate, or CRP, setting is the same as the Cisco ip pim rp-candidate setting. Use it to control which interface that should be used in RP elections.

• address | ifname: Optional local IPv4 address, or interface name to acquire address from. The default is to use the highest active IP address.

• time <10-16383>: The interval, in seconds, between advertising this CRP. Default: 60 seconds

• priority <0-255>: How important this CRP is compared to others. The lower the value here, the more important the CRP. Like Cisco, pimd defaults to priority 0 when this is left out

In the CRP messages sent out by pimd, one or more multicast groups can be advertised using the following syntax.

group_prefix <group>[</LENGTH> | masklen <LENGTH>]

Each group_prefix setting defines one multicast group and an optional mask length, which defaults to 16 if left out. A maximum of 255 multicast group prefix records is possible for the CRP.

To keep track of all Rendezvous Points in a PIM-SM domain there exists a feature called Bootstrap Router. The elected BSR in a PIM-SM domain periodically announces the RP set in Bootstrap messages. For details on PIM BSR operation, see RFC 5059.

cand_bootstrap_router [address | ifname] [priority <0-255>]

The configuration of a Candidate BootStrap Router (CBSR) is very similar to that of CRP, except for the interval time. If either the address or the interface name is left out pimd uses the highest active IP address. If the priority is left out, pimd (like Cisco) defaults to priority 0.

In a PIM-SM domain there can be two, or more, paths from a designated router (DR) for a multicast sender to reach a receiver. When receivers begin joining multicast groups all data is received via the shared tree (RPT) from each Rendezvous Point (RP). This is often not an optimal route, so when the volume starts exceeding a configurable threshold, on either the last-hop router or the RP itself, the router will attempt to switch to the shortest path tree (SPT) from the multicast source to the receiver.

In versions of pimd prior to 2.2.0 this threshold was confusingly split in two different settings, one for the DR and one for the RP. These settings are still supported, for compatibility reasons and documented in the man-page, but it is strongly recommended to change to the new syntax instead:

spt_threshold [rate <KBPS> | packets <NUM> | infinity] [interval <5-60>]

Only slightly different from the Cisco ip pim spt-threshold setting, pimd can trigger a switch to SPT on a rate or number of packets and you can also tweak the poll interval. It's recommended to keep the interval in the tens of seconds, the default is 100 sec. The default threshold is set to zero packets, which will cause a switch over to the SPT after the first multicast packet is received.

Example

# This pimd.conf example assumes a router with four interfaces.
# Interface eth0 is disabled, i.e., pimd will not run there.
# The default interface preference 101 has been changed on all
# the other interfaces.
phyint eth0 disable
phyint eth1 preference 255
phyint eth2 preference 250
phyint eth3 preference 251

# Offer to be an RP for all of 224.0.0.0/4
cand_rp eth1
group_prefix 224.0.0.0 masklen 4

# Partake in BSR elections as well
cand_bootstrap_router eth1

# This is the built-in defaults, switch to SPT on first packet
spt_threshold packets 0 interval 100

Starting

Having set up the configuration file, you are ready to run pimd. As usual, it is recommended that you start it manually first, to make sure everything works as expected, before adding it to your system's startup scripts, with any startup flags it might need.

pimd [-c file] [-d[level1,...,levelN]]

• -c file: Utilize the specified configuration file rather than the default, /etc/pimd.conf

• -d[level1,...,levelN]: Specifies the debug level(s) to utilize when running the daemon. Type pimd -h for a full list of levels

Example:

pimd -c /cfg/pimd.conf -digmp_proto,pim_jp,kernel,pim_register

Notice the lack of spaces in the option argument to -d, the long-option --debug=igmp_proto,pim_jp,kernel,pim_registeris slightly more readable.

Monitoring

To see the virtual interface table, including neighboring PIM routers, and the multicast routing table:

pimd -r

or to watch it continually:

watch pimd -r

In addition, pimd logs important events to the system logfile, in particular at startup when parsing the pimd.conf configuration file.