BGP DECISION PROCESS
1 largest weight ( local orininated path :32768 other 0 )
2 largest local-preefernce (BGP default local-preference )default 100
3 prefer local paths (decreasing preference :default -orininate in neighbor,default -information -orininate in global,network,redistribute,aggregated)
4 shortest as _path ('bgp bestpath as-path ignore' bypasses this step;AS_SET counts as 1 ;as_confed_sequence and as_confed_set are not counted)
5 lowest origin code (0 -igp,1-egp,2-imcomplete0
6 lowest med ('bgp always-compare-med;bgp bestpath med-confed;bgp bestpatch med missing-as-worst;bgp determinstic-med) default 0
7 ebgp prefered over ibgp (confed ,path are treated as internal paths)
8 closest IGP neighbor (best cost)
9 determine if multiple paths require installation (multipath)
10 if paths are external choose the oldest one (flap prevention ) skipped if "bgp bestpath comfare-routerid)
11 lowest router-id
12 minimum cluster-list length (RR enivronment)
13 lowest neighbor address
 
REGEXP
 .      single character
 *      zero or more
 +      one or more
 ?      zero or one
[]        range
[^]      negate range
^        begining of input
$        end of input
_         , () {} ^ $ ,space
\         escape special character
\1       repeat a match ()
|         logical OR
 
 
PATH ARRTIBUTES
 
<TYPE  ,LENGTH,VALUE>
            FLAGES                                          CODE
------------------------------------------------------------------------------------
0 | 1 |2 | 3 |                    |                                               |
-------------------------------------------------------------------------------------
0---------    0 Well-Known ; 1 -Optional
1--------      0  Non-transitive ; 1 =Transitive
2---------     0 Complete; 1 =Partial
3----------     0 1bytes  ; 1=2bytes (Attr len Field)
 
1 origin                             WK  M
2 as_path                           WK  M
3 next_hop                         WK M
4 MED                                ON  T
5 local_pref                        WK  D
6 atomin_aggreagte            WK  D
7 aggregator                       O   T
8 community                       O   T
9 originator_id                     O NT
10 cluster_list                     
12 advertiser                       
13 rcid_path/cluster_ID         
14 mp_reachable NLRI         O NT
15 mp_unreachable NLRI      O NT
16  extended communities
 
 
Filter Sequence :
 
 
IN :
1 prefix-list
2 filter-list
3 weight
4 route-map
 
OUT:
1 prefix-list
2 filter-list
3 router-map
 
IGP:
1 distribute-list
2 route-map (redistribution)