NDI will attempt to use different multicast addresses to ensure that the streams can be filtered efficiently by the network adapter. x and above versions) The following C++ code snippet shows how to change May 31, 2013 · 13. Jan 8, 2013 · LWIP_MULTICAST_TX_OPTIONS==1: Enable multicast TX support like the socket options IP_MULTICAST_TTL/IP_MULTICAST_IF/IP_MULTICAST_LOOP, as well as (currently only) core By default, IP multicast datagrams are sent with a time-to-live (TTL) of 1. 8 port 5001 [ 3] local 10. A multicast packet received on an interface is flooded unconditionally to all interfaces (except the incoming interface) belonging to the same forwarding The IP_MULTICAST_TTL socket option allows the application to primarily limit the lifetime of the packet in the Internet and prevent it from circulating indefinitely. Vlan25 is up, line protocol is up. These multicast packets have a local scope thanks to their TTL so they are not routed. I cannot change the sender/applications on the remote station to increase the TTL but I must route the IPV6_MULTICAST_HOPS The IPv6 header contains a hop limit field that controls the number of hops over which a datagram can be sent before being discarded. The table below describes the significant fields shown in the display. R1# ip route add 224. 26 and 5. Parse("239. config system settings set multicast-forward enable end Prevent the TTL for forwarded packets from being changed. If not otherwise specified, multicast datagrams are sent with a default value of 1, to prevent them to be forwarded beyond the local network. When a multicast router receives the message, it will do an RPF check on the source address of the BSR and will re-send the message Multicast TTL provides the ability to limit or extend the hop limit of a DM NVX stream that traverses routers. 1. Oct 14, 2015 · Of course, one can ensure that multicast datagram never leave A, by creating and enforcing a loopback device for multicast: sudo ifconfig lo multicast. Oct 10, 2011 · Here is the output. Take a look at the man pages for ip and setsockopt. PS: 6. The default multicast TTL setting is 5. 1 -u -T 3 -t 100 -i 1 (note it is set up as client uploading to group address, T switch is for TTL) On Multicast client, Mar 17, 2024 · When multicast-forward is enabled on a FortiGate firewall, it will forward multicast IP packets with a TTL value of 2 or higher, while reducing the TTL in the IP header by 1. C#. if your forwarding state is good on all routers, then check the TTL value on traffic sent by source. Also you can start multicast proxy. The default (0x0E) is for the global scope With multicasting, you work with a defined group of recipients, based on options such as IP address ranges, the ability to enable/disable multicast for individual cameras, the ability to define largest acceptable data packet size (MTU), the maximum number of routers a data packet must be forwarded between (TTL), and so on. 20 port 39731 connected with 224. Any view v1. Using socket. When you receive a multicast, I thought you just tell the kernel to join a multicast source (using the ip igmp join-group command). May 2, 2013 · The TTL value controls whether packets are forwarded out of an interface. By default all multicast packets have a TTL of 1 which means they will not be routed at all. We use routing protocols to learn different networks and to fill the routing table. 0, 20 March 1998 This HOWTO tries to cover most aspects related to multicast over TCP/IP networks. 0/8 on all routed interfaces at the perimeter of its network. 0, 20 March 1998. RTI Connext 4. Y también tenemos el tráfico IP Multicast que es del que vamos a hablar ahora en detalle. 16. Any IP multicast datagrams or state-refresh packets with a TTL less than this threshold will not be forwarded out the interface. HRD Logbook. This opens the “Stream Output” dialog showing the source file you have chosen. It is a numerical value set in a DNS record on the domain’s authoritative domain name server. Multicast TTL can be set to any value ranging from 1 to 255. † During the registering state, if the switch is the first-hop router to the source in PIM sparse mode (in this case, the switch must send PIM-register messages to the rendezvous point [RP]). IP_MULTICAST_TTL, 1) # This defines to which network interface (NIC) is responsible for # transmitting the multicast datagram; otherwise, the socket # uses the default interface (ifindex = 1 if loopback is 0) # If we wish to transmit the datagram to multiple NICs, we # ought to create a socket for each NIC. In other words: when it receives an IP packet it has to look at the destination address, check the routing table and figure out the next hop where to forward the IP packet to. InterNetwork)) Also all routers need to be configured to point to the same RP address, unless the igmp join has information about the source address. IP_MULTICAST_TTL: Sets the Time To Live (TTL) in the IP header for outgoing multicast datagrams. The ttl must be in the range 0 <= ttl <= 255 or an IllegalArgumentException will be thrown. # tcpdump -i eth0 host 224. I assume since you'll be running tcpdump or tshark that you have root permission. Configuring the TTL for PTP Packets To set the Time To Live (TTL) of PTP packets, use the ptp ttl command. The router will receive packets on this interface normally. Handling Multicast Data. The VLAN connected to the multicast source does By default, IP multicast datagrams are sent with a time-to-live (TTL) of 1. In other words, an IG bit of 0 indicates that this is a unicast MAC address, an IG bit of 1 Dec 16, 2022 · Some of the most common problems found when you implement IP multicast in a network are when the router does not forward multicast traffic because of either a RPF failure or TTL settings. The IP_MULTICAST_TTL socket option allows the application to primarily limit the lifetime of the packet in the Internet and prevent it from circulating indefinitely. Gets or sets the TTL value associated with IPv6 multicast traffic on the socket. The multicast UDP support in HRD Alert is enabled by the following settings in the HRD Alert Options dialog: Examples. 09:23:26. This raises some subsequent questions though. sender. Use this parameter to limit multicast packets distribution via gateways. I have adapted some code from this post which in its edited form supposedly works, but does not for me. Multicast TTL threshold is 0. Juan-Mariano de Goyeneche <jmseyas@dit. Is it possible to change the TTL values of outgoing multicast packets with any system parameter (like sysctl)? Is it possible to change the TTL of outgoing multicast packets using iptables? The BSR sends messages on a hop-by-hop basis and does so by sending its packets to multicast address 224. I am trying to send "HELLO" to a UDP server, but I would like to change the interface to one of the local IP addresses. multicastTTL property) determines the range over which a multicast packet is propagated in your intranet. Sets the multicast datagram time-to-live (router hop-count) threshold for the VLAN. Dec 12, 2012 · Here’s how to do it: In the Media menu, choose “Stream”. The main goal of a router is to route packets. 0, Tunnel3. The -t option for ping will do this, and other programs will have different options. The default value is 0, which means that all multicast packets are forwarded on the interface. Dec 18, 2020 · Though in SDA we provide subnet across FEs and mobility between them, The multicast however works over L3 and not L2 even when source and receiver are in same subnet but attached to different FEs. Oct 15, 2014 · Hi, This question has been asked before but I couldn't find a definitive solution to the issue (CISCO suggestion was to increase TTL on the sender side). It refer to "IG bit" that is present in the Ethernet Frame. In this case, all OSPF routers will listen to 224. switch(config)# Oct 31, 2002 · Prior to analyzing the multicast management code, it is worth spending a couple of words on the TTL array, a member of the mfc_cache structure. The TTL value can be adjusted in the transport property. May 22, 2012 · For a SENDING multicast socket on a multi-homed server, it is very important to create a separate socket for each interface you want to send to. Use this command if you want to use TTL to examine your multicast data traffic. Here is my code. 0/4 dev eth1 R1# iperf -u -c 225. Mar 22, 2021 · As a result, I am trying to send the IGMP packet with TTL > 1. Aug 4, 2022 · There might be many reasons for sending a TTL 1 in Multicast and broadcast packets. I explored and found that I can use iPerf for multicast also. Anycast. 254/24. All i want to do is do a multicast to all machines on the network. Here is what I used for iPerf: On Multicast source, iperf -c 239. No multicast groups joined by this system. To allow multicast forward packet with TTL = 1, use the following option: config system settings. With Wireshark (2. I would like to do the same thing, but for multicast packets. You can use the multicast-ttl-notchange option so that the FortiGate does not increase the TTL value for forwarded multicast packets. es>. IPPROTO IP_MULTICAST_IF: Sets the interface over which outgoing multicast datagrams should be sent IP_MULTICAST_TTL: Sets the Time To Live (TTL) in the IP header for outgoing multicast datagrams IP_MULTICAST_LOOP: Specifies whether a copy of an outgoing multicast datagram should be delivered to the sending host as long as it is a member of the Use display multicast minimum-ttl to display the minimum TTL required for a multicast packet to be forwarded on the specified interface or all interfaces. It uses specially reserved multicast address blocks in IPv4 and IPv6 . Every time a router forwards the packet, it decrements the TTL field in the packet header, and if the value reaches zero, the packet is dropped. 3 -T 3 R4# iperf -s -u -B 225. Custom TTL: Multicast TTL provides the ability to limit or extend the hop limit of a DM NVX stream that traverses routers. I am trying to get some simple UDP communication working on my local network. 4444: UDP, length 10. --ttl-inc value - Increment the TTL value ‘value’ times. To change the TTL to the value you desire (from 0 to 255), put that value into a variable (here I name it "ttl") and write somewhere in your program: 4. 13 with a TTL of 1. Use tcpdump -A if you want to confirm the message is 1234567890. Only relevant with IPv4/IPv6 UDP transports. g. May 13, 2016 · Allow the multicast traffic: Also you might need to add the route for multicast traffic: Change the TTL of the multicast sender: iptables -t mangle -A OUTPUT -d <group> -j TTL --ttl-set 128 Where group is the multicast group address of the stream you want to change the TTL of. --ttl-dec value - Decrement the TTL value ‘value’ times. 20 port 42652 connected with 224. Time to live ( TTL) or hop limit is a mechanism which limits the lifespan or lifetime of data in a computer or network. end. Figure 33-6 shows that Company XYZ has an administratively-scoped boundary set for the multicast address range 239. 0 dev lo. The following example demonstrates how to join a multicast group by providing two parameters, a multicast address, and a number that represents the TTL. IGMP is the Internet Engineering Task Force (IETF) standards track protocol used for hosts to signal multicast group membership to routers. 0/16 [100/11] uptime 07:55:50, expires 00:02:52 via 192. gethostbyname(socket. El tráfico Multidifusión está asociado específicamente a un grupo de «clientes» interesados en recibir ese tráfico de red, si no está en el grupo de Multicast, no recibirán la información, esto es algo ideal para no colapsar las redes, ni tener que enviar copias de todos los paquetes a todos Apr 29, 2022 · Time-to-Live (TTL) in DNS: DNS TTL refers to the time taken by DNS for caching a record. The problem is ip maddress only affects link layer multicast addresses not protocol multicast addresses (man 8 ip-maddress). This Question Provided some valuable insight on how to set the default TTL for IP packets on a system. Click Next to set destination. multicastTTL property to an integer between 1 and 255. This ability is used to control the scope of the multicasts. with ping) ensure the TTL is set larger than one. Example This command configures a TTL of 64 hops for PTP packets. The default value is 15. Multicast allows a single network packet to be delivered to a group of receivers. Multicast packets sent with a TTL of 0 are not transmitted on the network but may be delivered locally. This allows you to use one TTL for multicast and one TTL for unicast. A bound SENDING socket should be created for each interface. Only multicast packets with a TTL greater than the threshold of the interface are forwarded. [2] [3] Multicast differs from physical layer point-to-multipoint communication . 4. In fact, for each multicast address assigned to every interface, we have a single byte value identifying the TTL threshold. IP addresses in the range 224. The default value of the multicast TTL is 255, which means, theoretically, that the packet Oct 14, 2023 · When testing multicast routing (e. 168. 2. ping-t 4 ff05:: 1 1, enable it: config system settings set multicast-forward enable # enable forwarding mutlicast messages at all set multicast-ttl-notchange enable # keep TTL untouched and pass on end. Related Information Aug 13, 2020 · Only multicast packets with an IP header TTL greater than or equal to the ttl-value argument are sent to the MSDP peer specified by the IP address or name. The IG bit distinguishes whether the MAC address is an individual or group (hence IG) address. IGMP snooping is globally enabled. but the corresponding packets are never received. 8. Learn how to configure multicast forwarding on FortiGate devices with this cookbook guide. The IPV6_MULTICAST_HOPS socket option can be used to set the default hop limit value for an outgoing multicast packet. public void SendMessage(string message) var data = Encoding. The following example shows output of the showipdvmrproute command: Router# show ip dvmrp route DVMRP Routing Table - 1 entry 172. [1] Multicast can be one-to-many or many-to-many distribution. I have incoming multicast packets with TTL=1 from a third party station/applications. Examples. Internet address is 10. You should use multicast boundaries instead of TTL thresholds to limit the forwarding of multicast traffic outside of a domain or a subdomain. IGMP is disabled on interface. When multicast-skip-policy is enabled, no check is performed based on multicast policy. IPAddress multicastIpAddress = IPAddress. The default value of 0 means all multicast packets are forwarded out the interface. See full list on cisco. Multicast TTL Threshold—Enter the Time-to-Live (TTL) threshold of packets being forwarded on an interface. Enter configuration commands, one per line. When an IP packet is sent, an IP header field called Time To Live (TTL) is set to a value between zero and 255. This requires every HOP to decrement TTL. 2 IP_MULTICAST_TTL. This command only affects transmission of multicast packets: Router1# configure terminal. Multicast streams are config system settings set multicast-ttl-notchange enable end Multicast processing in transparent mode. 5 nd 224. Here is my sending code. 8, UDP port 5001 Sending 1470 byte datagrams Setting multicast TTL to 3 UDP buffer size: 208 KByte (default) setting perf ip4 ttl to 3 [ 4] local 10. Ensure that the Accept UDP requests, Notify on accepted UDP request and Accepted UDP request restores window checkboxes are ticked. Then, on the video client hosts: ffplay udp://239. Only multicast packets with a TTL greater than the interface TTL threshold are forwarded on the interface. The multicast stream will be able to traverse up to 8 routers because the TTL is set to 8. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Any Ethernet, or other 802. This administrative region is specified in terms such as "this site", "this company", or Nov 21, 2013 · You can configure it per socket, using the IP_MULTICAST_TTL setsockopt() flag. 0 netmask 240. Multicast has a couple of fundamental characteristics that dictate how it’s used. To make multicast work in your environment , you have to increase the TTL from 1 to 10 in VLC media player (say for example) to avoid multicast stream packets from being dropped at first hop router. † If the multicast TTL threshold is configured on an outgoing interface for the flow (using . May 16, 2024 · Multicast is used for everything that broadcast was previously used for, including a number of standard network infrastructure things like router discovery, address allocation, and neighbour discovery (which replaces ARP ). Multicast configuration has a parameter that specifies the time to live (TTL) for multicast packets. So, a lot of information within it is not Linux−specific (just in case you don't use GNU/Linux yet). If there are issues with the application, it may also cause the stream to be sent with an incorrect value as well. 0. Along with unicast options, all multicast ones seen here are handled: IP_MULTICAST_TTL, IP_MULTICAST_LOOP, IP_MULTICAST_IF, IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP. 6 version for Linux) is possible to choose the filter " eth. IP_ADD_MEMBERSHIP and bind() are only required for receiving multicast, use IP_MULTICAST_IF instead for effectively a "send-only membership" of a multicast group. As an example: Setting the TTL to 1, will limit the packet propagation to the LAN. The default value of 0 means that all Multicast packets are forwarded on the interface. 3 on UDP port 4567. display multicast [ all-instance | vpn-instance vpn-instance-name ] minimum-ttl [ interface-type interface-number ] [ | { begin | exclude | include} regular-expression] Views. Currently, I am using UdpClient. UdpClient udpClient = new UdpClient(); // Creates an IPAddress to use to join and drop the multicast group. The multicast TTL is configured by setting the net. 4 and port 444. You specify the TTL value in hops. For example, you could limit internal traffic to a TTL of 8. Multicast Routing. 6509Switch#sh ip igmp inter vlan 25. By default, IP multicast datagrams are sent with a time-to-live (TTL) of 1. v1. TTL is the maximum number of hops that a PTP packet may make. Jan 15, 2009 · Don’t ever set or increment the value on packets that leave your local network! mangle table: --ttl-set value - Set the TTL value to ‘value’. slp. In other words, the duration for which a DNS record is to be kept or the time it takes for a DNS record to be returned from the cache is referred to as time-to-live. Once a socket has joined a multicast group, handling incoming data is similar to handling any UDP packet, albeit with the Mar 5, 2020 · Which term describes a field in the IPv4 packet header that contains a unicast, multicast, or broadcast address? destination IPv4 address; protocol; TTL; header checksum; Exam with this question: Modules 8 – 10: Communicating Between Networks Exam Answers udp_ttl: 1: Specifies the TTL value for IPv4 multicast messages and the hop limit for IPv6 multicast messages. Multicast. Use this option only if packets are expiring before reaching the multicast router. This is similar to the TTL field in the IPv4 header. There are applications which work within same subnet with TTL=1 which doesn't work in SDA. Multicast routing is disabled on interface. Jun 2, 2014 · config system settings set multicast-forward enable end Prevent the TTL for forwarded packets from being changed. udp6_scope: 0x0E: Specifies the scope for IPv6 multicast messages (RFC 4291). This option is only valid for datagram and raw sockets (the socket type must be SOCK_DGRAM or SOCK_RAW). Nov 5, 2023 · If not set, the default TTL is typically 1. x and above uses a default multicast time-to-live (TTL) value of 1. Previously to the switch , a test is made to determine whether the options are multicast router specific, and if so, they are routed to the ip_mroute_setsockopt() and ip_mroute The multicast time to live ( net. Mar 26, 2018 · These options actually function differently. . ig == 1 ". It is the IP-specific form of multicast and is used for streaming media and other network applications. To function, Layer 3 aware devices listen to join and leave messages from clients wanting to join and leave multicast groups through use of an IGMP Querier, common setups rely on a Designated Querier (DQ) per VLAN. Alpha2, without any success. gethostname()) to select the interface doesn't always elect the external interface - in fact, on debian systems, it tends to select the loopback address. Syntax. 7. I have been trying to get UDP multicast working with Netty 4. Copy. 255. x, address with a high-order bit set to 1 (that is, if its first octet is odd) is multicast, except for the Broadcast address (which is all ones). In the Open Media dialog file tab, click “add” and choose the file you want to stream and click “Open”. 2. If you dont have tcpdump, wireshark or pcap will see it too. set multicast-ttl-notchange enable. Multicast datagrams with TTL greater than 1 may be forwarded to other networks if a multicast router is attached to the local network. ソケットオプション ip_multicast_ttl を指定すると、後続のマルチキャストデータグラムの ttl を 0 〜 255 の範囲の任意の値に設定してマルチキャストの配信範囲を制御できます。 Now, to the actual test case. In contrast, setting the IP_TTL option (at least on Linux) only affects outgoing unicast datagrams. For this purpose, the client making the request sends (according to the current cache entry) the reply that, in their opinion, is correct. Very useful if you want to use PIM/DVMRP or similar in the next step! Dec 1, 2022 · Routers also use IGMP to advertise multicast group memberships to neighboring switches and routers. You can find the TTL by selecting any packet of the multicast stream, and expanding its "IPv4 IP multicast is a method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. For hosts with multiple interfaces, where an interface has not been specified for a multicast group membership, each multicast transmission is sent from the primary network interface. As a result , the multicast stream packets are dropped at the first hop router. The attached code simply echoes "Send 1", "Send 2" etc. According to a blog post The ttl-threshold command instructs the router to drop any multicast packets that have a TTL value less than or equal to the specified value. Protocols associated with IP multicast Jan 20, 2021 · 1. There are similar flags for IPv6, namely Sep 11, 2023 · With the Multicast mode, the server sends one copy of data to a multicast address, and each client will receive data at a speed of 100 MB per second. Multicast is currently an active area of research and, at the time of writing, many of the Aug 10, 2020 · The multicast DNS creates a relatively large amount of traffic, yet attempts to save active network resources. 0 to 239. The socket option IP_MULTICAST_TTL allows the TTL for subsequent multicast datagrams to be set to any value from 0 to 255. 8 port 5001 Jul 6, 2011 · The output will be streamed to multicast address 239. In IPv4 multicasting, routers have a TTL threshold assigned to each interface. This page indicates that application code can set the multicast TTL with a call to setsockopt () with the flag IP_MULTICAST_TTL, stating Jun 17, 2014 · When the TTL of received packet reaches 0 after processing, it will still process the packet, if it is destinated to self or any multicast address to which it is listening to. Discover the benefits and requirements of multicast routing and IGMP. To assign a Jul 22, 2014 · Multicast in Python has one of the answers with a TTL as 32 on the receiving side (and IP_MULTICAST_LOOP as 1), but I'm having a hard time figuring out why. At the bottom, click the “Stream” button. By default , in VLC multicast packets are sent with TTL = 1. Only when this is no longer correct, or when the entry is about to expire, does the recipient Nov 11, 2017 · Protocol Independent Multicast (PIM) SSM, or PIM-SSM, is the routing protocol that supports the implementation of SSM and is derived from PIM sparse mode (PIM-SM). 6. Multicast is currently an active area of research and, at the time of writing, many of the "standards" are merely drafts. TTL of 0 are not transmitted on any sub-network. This administrative region is specified in terms such as "this site", "this company", or setting perf ip4 ttl to 3 Client connecting to 224. Multicast packets with a TTL value less than the threshold aren’t forwarded on the interface. This HOWTO tries to cover most aspects related to multicast over TCP/IP networks. upm. Something like the following: We use Multicast with java applications and the system tags our multicasts packets with a ttl=1 which cause the packet to be dropped by the next hop device. But now, if I want to consume the UDP datagram simultaneously in another linux box, say, "B", there is no way they arrive there. This value prevents the datagrams from being forwarded beyond a single subnetwork. So, a lot of information within it is not Linux-specific (just in case you don't use GNU/Linux yet). The first command for R1 adds a route for all multicast packets, that is necessary for all tools where you cannot set the outbound interface for the multicast stream, in our case iperf. it could be too low and cause packets to be dropped before reaching the receiver. 2, Create multicast policies to actually allow the traffic to pass. GetBytes(message); using (var udpClient = new UdpClient(AddressFamily. 3:4567 The client hosts will play the video received on the multicast stream. ; The Cradlepoint will only forward multicast packets if the TTL of the packet received is higher than the TTL threshold, which has a default value of 1. 43. Next: Administrative Scoping Up: Multicast Scoping Previous: Multicast Scoping TTL Scoping. Method One for modifying the TTL (applies to all 4. Jul 30, 2012 · I have a Computer with 5 interfaces: 3 with public IPs and 2 local IPs. Jul 20, 2022 · The value of 1 in the Multicast TTL: field is suitable. 255 (224/4) have been Nov 26, 2018 · This example doesn't work for me, for an obscure reason. This option also serves to allow the application to specify administrative boundaries. com RFC 1112 Host Extensions for IP Multicasting August 1989 To allow multicast transmissions, the routing logic must be changed to: if IP-destination is on the same local network or IP-destination is a host group, send datagram locally to IP-destination else send datagram locally to GatewayTo( IP-destination ) If the sending host is itself a member of the destination group on the outgoing Jul 26, 2011 · and you should see a 10 byte UDP packet arrive using tcpdump on the server. Socket option for time-to-live associated with outgoing multicast packets. // This is a fix for that bug that causes Servers to pop offline/online. sudo route add -net 224. By default it is set to 1. IPV6_MULTICAST_IF: yes: yes: DWORD: Gets or sets the outgoing interface for sending IPv6 multicast Dec 23, 2019 · Important notes about TTL (Time to Live): The TTL (Time to Live) is set by the device that originates the multicast traffic, and decreases by 1 with each routed hop. 56837 > 224. In computer networking, multicast is a type of group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast datagrams with a TTL of greater than 1 may be delivered to more than one sub-network, if there are one or more multicast routers attached to the first sub-network. Once the prescribed event count or timespan has elapsed, data is discarded or revalidated. Oct 5, 2020 · Some applications use a default TTL of "1" that will need to be adjusted, as a value of "1" indicates that the packet isn't routable. In computer networking, TTL prevents a data Apr 1, 2015 · 1. JoinMulticastGroup () with the TTL parameter set to 3, but when I examine the IGMP packet with Wireshark, the TTL stays at 1. I did Set the default time-to-live for multicast packets sent out on this MulticastSocket in order to control the scope of the multicasts. 3. Refer to the IP Multicast Troubleshooting Guide for a detailed discussion about these and other common problems, symptoms, and resolutions. 255"); Jun 3, 2010 · And for multicast testing, I used a rather simpler way, iPerf. Setting IP_MULTICAST_TTL only affects outgoing multicast datagrams, not unicast datagrams. NDI senders need a range of multicast addresses available. This means that, by default, multicast traffic will not cross subnet boundaries. Each value of the array is linked directly to the vif_table. The default (1) restricts messages sent by ptp4l to the same subnet. I do not know if this is possible. The TTL value controls how many “hops” the multicast sending traffic will take, allowing it to move outside the local network. Default. IP_MULTICAST_IF sets the kernel to send multicast packets for a given group on a given interface, it is effectively "send-only" as you will not be able to receive traffic on that group after setting. typedef implementation_defined hops; Implements the IPPROTO_IP/IP_MULTICAST_TTL socket option. I was reading Multicast Programming and I don't understand why TTL and LOOP are necessary for the receiver. 694624 IP srchost. setsockopt (socket. 20. It is illegal to set the TTL to a value greater than 255. That being said using the autojoin flag with the address verb does the trick just nicely. wa vs xh vs pa zf aa tr bn mm