BGP route selection

[Arvin Gan]

Hi all,
   Sorry, it's my ambiguous description. What I said default value is Cisco's admin distance value, eBGP is 20 and iBGP is 200. We plan to use preference to implement  admin distance. Actually ,in bird,  the preference of channel for BGP is  BGP protocol default preference DEF_PREF_BGP ( = 100). 
     1)  Since the configuration of preference is in channel ,if the protocol have more than one channel, does mean different channel can configure different preference  in the same protocol ?
     2) I also notice that " new->pref = c->preference; " in rte_update2, does mean  the preference of route in route table get from  preference of channel ?    
     3)  When route selection, does mean algorithm selection compare preference of every route firstly , whether compare  the preference of  routes coming from same protocol ?  
    
The global best route selection algorithm is (roughly) as follows:  ---> Does routes selection be processed as below sequence ?

   *   Preferences of the routes are compared.  ----> what's preference of the route, is preference in channel-config ?
   *   Source protocol instance preferences are compared. --> what's protocol instance preference, is preference in channel-config for BGP protocol instance?
   *   If source protocols are the same (e.g. BGP vs. BGP), the protocol's route selection algorithm is invoked. --->source protocols, iBGP and eBGP are treated as same source protocol ?
   *   If source protocols are different (e.g. BGP vs. OSPF), result of the algorithm is undefined.

The Admin distance of Cisco for eBGP and iBGP:  
https://supportforums.cisco.com/t5/wan-routing-and-switching/administrative-distance-and-bgp-path-selection-process/td-p/2276230

Thanks
Arvin

-----Original Message-----
From: Bird-users <bird-users-bounces at network.cz> On Behalf Of Robert Blayzor
Sent: Tuesday, April 17, 2018 10:07 PM
To: bird-users at network.cz
Subject: Re: BGP route selection

On 4/17/18 8:20 AM, Ondrej Zajicek wrote:
> Hi
> 
> No, default value is 200 for both EBGP and IBGP. Where did you noticed 20?


20 is Cisco's default admin distance for EBGP.

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