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Re: [magma] About source IP address of IGMP Join sent on loopbackinterface

"Prashant Jhingran (pjhingra)" <pjhingra@cisco.com> Mon, 22 March 2010 09:03 UTC

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Thread-Topic: [magma] About source IP address of IGMP Join sent on loopbackinterface
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From: "Prashant Jhingran (pjhingra)" <pjhingra@cisco.com>
To: preetham B <preetham.b79@gmail.com>
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Subject: Re: [magma] About source IP address of IGMP Join sent on loopbackinterface
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Hi,
 
What you are seeing is expected, that's because 127/8 is reserved for
loopback address which cannot be used as source IP address while
communicating with outside world.

Regards,
Prashant Jhingran

  
 


________________________________

	From: magma-bounces@ietf.org [mailto:magma-bounces@ietf.org] On
Behalf Of preetham B
	Sent: Monday, March 22, 2010 1:36 PM
	To: magma@ietf.org
	Subject: [magma] About source IP address of IGMP Join sent on
loopbackinterface
	
	
	Hi, 
	
	I am running a host application which joins multicast group on
loopback interface.
	
	But the source IP address of IGMPv3 report is not loopback
address (127.0.0.1).
	Its picking up first available N/W interface address. 
	
	
	
	Snippet:
	 mreq.imr_multiaddr.s_addr = inet_addr("239.5.1.7");
	 mreq.imr_address.s_addr = htonl(INADDR_LOOPBACK);
	 mreq.imr_ifindex = 1; (Interface index of loopback)
	 check(setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,
sizeof(mreq)) == 0);
	
	
	
	Is there any reason why loopback address is not source IP
address of join message?
	
	Regards,
	Anupama

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