[j-nsp] MED problems

[Harshit Kumar]

Hi Jonas,
       
 By default MEDs are compared only in case of routes learned from same
 neighboring AS. In this case they are from different AS's .

>AS path: 13237 24940 I
> AS path: 12337 24940 

The route selection in bgp is governed by various factors which 
 are listed in the link below. You can see why a route lost a 
 battle in "Inactive reason: Router ID". So in your case route 
selection skipped MED check and lost the war in having lower router-id.

http://www.juniper.net/techpubs/software/nog/nog-baseline/html/verify-bg
p9.html

http://www.juniper.net/techpubs/software/junos/junos63/swconfig63-routin
g/html/bgp-config34.html

Hope that helps ..
Harshit  

>-----Original Message-----
>From: juniper-nsp-bounces at puck.nether.net 
>[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Jonas Frey
>Sent: Friday, May 28, 2004 5:18 PM
>To: juniper-nsp at puck.nether.net
>Subject: [j-nsp] MED problems
>
>Hello,
>
>i've got a strange problem with using med's:
>
>*BGP    Preference: 170/-101
>Source: 1.0.0.233
>Next hop: 1.0.0.233 via so-0/3/3.0, selected
>Protocol next hop: 10.0.0.233 Indirect next hop: 8704180 441
>State: <Active Int Ext>
> Local AS: 1000 Peer AS: 1000
>Age: 33:02      Metric: 5       Metric2: 0 
>Task: BGP_1000.10.0.0.233+179
>Announcement bits (4): 0-KRT 1-RT 2-BGP.0.0.0.0+179 3-Resolve inet.0 
>AS path: 13237 24940 I
>Localpref: 100
>Router ID: 10.0.0.233
>
>
>BGP    Preference: 170/-101
>Source: 10.0.0.254
>Next hop: 10.0.0.254 via ge-0/1/0.0, selected
>Protocol next hop: 10.0.0.254 Indirect next hop: 87040c0 301
>State: <Int Ext>
>Inactive reason: Router ID
>Local AS: 1000 Peer AS: 1000
>Age: 47:57      Metric: 0       Metric2: 0 
>Task: BGP_1000.10.0.0.254+3114
>AS path: 12337 24940 I
>Localpref: 100
>Router ID: 10.0.0.254
>
>AFAIK the router should use the later path because of the higher med on
>the first route. However it seems it ignores it?!
>Or maybe its just too late and i cant figure out the obvisous :)
>
>(Note: I have replaced the router IPs/IDs/AS with private ones, however
>i left the last number of the ips the real one. And yes: both routers
>have the same first 10.0.0.x IPs.)
>
>Using JunOS 6.2R2.4.
>
>Regards,
>Jonas Frey
>
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