How do sFlow recover AS numbers?

Hi sflow users,

I am Gregory, currently working at Nara Institute of Science and Technology (NAIST).
For the moment, I am using sFlow in my research and I tried to store sFlow packets to a database using sflowtools, which I did. Then, I noticed there was some errors concerning the AS numbers. Some AS numbers are reported as 0 (when it is equal to the sFlow agent AS number) while it is not the case. I think the topology I am running is working well but maybe it need some modifications.
Actually, this problem occurs between two border routers. Let assume these two router from AS 100 and AS 200 share VLAN 1030/2030 (each AS has its own VLAN number) with respective IP addresses 10.1.255.10 and 10.1.255.200.
Note that 10.1.0.0/16 is the network of AS 100. Network of AS 200 is 10.2.0.0/16
In BGP, I declare each other neighbor-relationship.
The BGP tables show the following :
for 10.1.255.10 :
*> 10.1/16 ---------------- - 100 10 i
*> 10.2/16 10.1.255.20 - 100 10 200 i
for 10.1.255.20 :
*> 10.1/16 10.1.255.10 - 100 10 100 i
*> 10.2/16 ---------------- - 100 10 i

But when, I ping from inside AS 100 to 10.1.255.20, assuming 10.1.255.10 is the sflow agent, the sflowsample will put 0 for both source and destination AS numbers meaning both are equal to current AS number (sflow agent ASN) = 100.
It is the case for source AS number as AS 100 is originating the ping but not the case for 10.1.255.20 which is the AS 200 border router.

Then my question is : is sFlow using ip routes tables instead of BGP tables to recover AS numbers on a flow path?
                                       
Other question to help me in my work : if I have to modify my routers configuration, what shall I do? (concerning VLANs, network interfaces and BGP routing, etc.).

Thank you in advance for any information you could provide me with.

Gregory BLANC.
Received on Thu Apr 19 03:52:49 2007