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239.255.255.253:1900 and 239.255.255.250:427 causing alot of chatter on network

Posted on 2006-11-20
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I noticed my network slowing down today and when I logged into my traffic grapher, I saw ALOT of chatter between 239.255.255.253 port 427, 239.255.255.250 port 1900 and my Cisco switches
What are these two addresses?
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Question by:jskewes
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by:Steve Knight
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Hi, that is a multicast address.  Quick check shows it is 239.255.255.253 - SLPv2 Discovery.

I know SLP is (or can) be used in TCP/IP based Novell NetWare server installations and it looks like it can be used with Unix and Window boxes too with the right add-ons.... are you in a NetWare 5/6 environment by any chance?

Do you happen to know what this multi-cast traffic was like before your network slowed?

To quote from RFC 3082

"The Service Location Protocol (SLP) provides mechanisms whereby
   service agent clients can advertise and user agent clients can query
   for services.  The design is very much demand-driven, so that user
   agents only obtain service information when they specifically ask for
   it.  There exists another class of user agent applications, however,
   that requires notification when a new service appears or disappears.
   In the RFC 2608 design, these applications are forced to poll the
   network to catch changes.  In this document, we describe a protocol
   for allowing such clients to be notified when a change occurs,
   removing the need for polling.
"


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jimmymcp02 earned 500 total points
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see if this helps
239.255.255.253 port 427
http://forums.macosxhints.com/archive/index.php/t-10978.html

239.255.255.250
http://www.grc.com/port_1900.htm
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by:mikebernhardt
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Those addresses are multicast addresses. Windows has a service called SSDP that tries to do network discovery using them. You should turn it off in the Services configuration on your PCs, you don't need it.
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by:jskewes
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This is the first time I'm seeing this and it seems to be talking to non-windows boxes.
should I block these addresses or services?
How would I go about blocking this?
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by:Steve Knight
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When you say non-windows..... Unix, netware, what else?
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by:jimmymcp02
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probably apple machines
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by:jskewes
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no Apples on our network. At all.
I think they are Cisco switches.
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by:WGhen
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Hve you turned on multicasting lately...
Cisco has this to say...

IP Multicast Group Addressing
A multicast group is identified by its multicast group address. Multicast packets are delivered to that multicast group address. Unlike unicast addresses that uniquely identify a single host, multicast IP addresses do not identify a particular host. To receive the data sent to a multicast address, a host must join the group that address identifies. The data is sent to the multicast address and received by all the hosts that have joined the group indicating that they wish to receive traffic sent to that group. The multicast group address is assigned to a group at the source. Network administrators who assign multicast group addresses must make sure the addresses conform to the multicast address range assignments reserved by the Internet Assigned Numbers Authority (IANA).

IP Class D Addresses
IP multicast addresses have been assigned to the IPv4 Class D address space by IANA. The high-order four bits of a Class D address are 1110. Therefore, host group addresses can be in the range 224.0.0.0 to 239.255.255.255. A multicast address is chosen at the source (sender) for the receivers in a multicast group.



--------------------------------------------------------------------------------

Note The Class D address range is used only for the group address or destination address of IP multicast traffic. The source address for multicast datagrams is always the unicast source address.


WGhen
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by:jskewes
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as far as I know, I haven't done anything to start multicasting.
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by:lrmoore
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Some dynamic routing protocols use multicast.. OSPF is one for sure.
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by:instillmotion
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by:jimmymcp02
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Instillmotion perhaps im experiencing browser issues here but i got request when trying to access those site?
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by:instillmotion
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