[quagga-dev 3946] point-to-point interfaces on linux/ospf

J.J. Krabbendam jkrabbendam at aimsys.nl
Mon Feb 13 21:42:27 GMT 2006


I already asked the quagga-users list about this issue, but now I dived 
into the code and therefore I want to pose the question here as well.

I want to connect two linux ospf routers using (unnumbered) 
point-to-point interfaces. All point-to-point interfaces on a router 
should have the same ip-address assigned. 
Eg I have three point-to-point connections (using pppd)  from R1 to R2. 
The p2p interfaces on R1 have address and on R2 they have the 

At first I saw only ospf enabled on the first p2p interface. I made a 
kludge (using ifindex) and saw hello's be sent out on all three p2p 
interfaces. However, as soon as the system starts sending  database 
description packets, they are only sent on ppp0 and not on ppp1 and 
ppp2. I have been looking at ospf_write() in ospf_packet.c. For 
multicast addresses, each time a call to ospf_if_ipmulticast() is done 
that ends in doing a setsockopt() with IP_MULTICAST_IF using the 
ifindex. But it seens to only work for multicast addresses, not for 

I tried also the call setsockopt_ifindex() but it does not seem to 
accept an ifindex. So I more or less ran out of options.

Question: how do I send a unicast packet to a specific network interface 
using my setup or is it not possible?


Jaap Krabbendam.

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