[Xorp-users] Route Redistribution issue in BGP : Traces

[Santhosh Sundararaman]

Hi
Thanks Atanu and Kristian for your suggestions. I did some trace and 
tried to find what was happening.  Initially I changed the to {} rule to 
use the nexthop4 rule instead of neighbor rule as shown below.

        term "ospf_routes" {
            from {
                    protocol: "ospf4"
            }
            to {
                nexthop4: 172.16.10.3 /*the interface on this router that
					is used as the next hop for the peer*/
            }
            then {
		trace: 2
                accept /*adv ospf routes to EBGP Peer*/
            }
        }


A snippet of the trace is below.
[ 2006/10/26 17:37:46 TRACE xorp_bgp POLICY ] Policy filter result: BGP 
Export route: 10.11.15.0/24 <http://10.11.15.0/24> Full route: GenID is 1
CHANGED flag is set
SubnetRoute:
  Net: 10.11.15.0/24 <http://10.11.15.0/24>
  PAList:
        Next Hop Attribute 172.16.10.3 <http://172.16.10.3>
        Origin Path Attribute - IGP
        AS Path Attribute AsPath: [AS/65001]
        Multiple Exit Descriminator Attribute: MED=0: accepted
Basic VarRW trace:
Read 1: 0,1
Read 11: 172.16.10.3 <http://172.16.10.3>
Write 0: 2
Read 1: 0,1
Read 11: 172.16.10.3 <http://172.16.10.3>
Write 0: 2
Read 1: 0,1
Read 11: 172.16.10.3 <http://172.16.10.3>
Write 0: 2

I interpreted the Read 11: value (which was the same for every route's 
trace) as the nexthop value that i specified in the config.boot file 
(part of which ive listed above). I repeated the same, but this time i 
changed the rule in to{} neighbor as shown below.

        term "ospf_routes" {
            from {
                    protocol: "ospf4"
            }
            to {
                neighbor: 172.16.10.1
            }
            then {
                accept /*adv ospf routes to EBGP Peer*/
            }
        }

I noticed that the trace for this config had 0.0.0.0 for the Read: 
values as shown below. I believe this should have been the neighbor 
value specified in the policy in config.boot (172.16.10.1) and that the 
value is not being set in the policy varrw. And I guess this is why the 
policy was not working correctly when the neighbor rule was being used. 
I have attached a piece of the trace below.


[ 2006/10/26 17:26:07 TRACE xorp_bgp POLICY ] Policy filter result: BGP 
Export route: 10.11.15.0/24 <http://10.11.15.0/24> Full route: GenID is 1
CHANGED flag is set
PUSH flag is set
SubnetRoute:
  Net: 10.11.15.0/24 <http://10.11.15.0/24>
  PAList:
        Next Hop Attribute 10.10.11.1 <http://10.10.11.1>
        Origin Path Attribute - IGP
        AS Path Attribute AsPath:
        Local Preference Attribute - 100: rejected
Basic VarRW trace:
Read 1: 0,1
Read 16: 0.0.0.0 <http://0.0.0.0>
Read 1: 0,1
Write 0: 2
Read 1: 0,1
Read 16: 0.0.0.0 <http://0.0.0.0>
Read 1: 0,1
Write 0: 2
Read 1: 0,1
Read 16: 0.0.0.0 <http://0.0.0.0>
Read 1: 0,1
Write 0: 2


Kindly let me know if what im interpreting is right.

Thanks
Santhosh