Wired Intelligent Edge (Campus Switching and Routing)

Aruba 3810 Switch - How to Change The Remote BGP Route Selection by Configuring BGP Origin

MVP
MVP
Requirement:

This article discusses how to modify the BGP routing process to send the Origin value IGP to a BGP neighbor.



Solution:

In the following example, Rack3sw1 is receiving the 1.1.1.1/32 prefix from the neighbors 192.168.13.1 and 192.168.23.2. All BGP route selection items (Metric, AS-Path, Origin, etc.) have the same values for both BGP neighbors. The lowest IP address is being selected.

Rack2sw3# show ip route bgp 1.1.1.1

                          IP Route Entries to 1.1.1.1

  Destination        Gateway         VLAN Type      Sub-Type   Metric     Dist.
  ------------------ --------------- ---- --------- ---------- ---------- -----
  1.1.1.1/32         192.168.13.1    13   bgp       external   0          170


Rack2sw3# show ip bgp 1.1.1.1/255.255.255.255

  Local AS            : 13            Local Router-id  : 192.168.13.3
  BGP Table Version   : 79

  Network     : 1.1.1.1/32            Nexthop          : 192.168.13.1
  Peer        : 192.168.13.1          Origin           : incomplete
  Metric      : 0                              Local Pref       :
  Weight      : 0                            Calc. Local Pref : 100
  Valid       : Yes                           Type             : external
  Stale       : No
  Best        : Yes (Lower Peer IP Address) <=====*****=====
  AS-Path     : 12
  Communities :

  Network     : 1.1.1.1/32            Nexthop          : 192.168.23.2
  Peer        : 192.168.23.2          Origin           : incomplete
  Metric      : 0                              Local Pref       :
  Weight      : 0                            Calc. Local Pref : 100
  Valid       : Yes                           Type             : external
  Stale       : No
  Best        : No
  AS-Path     : 12
  Communities :


The Origin selection is being advertised by switches Rack2sw1 and Rack2sw2 with a value of “incomplete” (?) for the prefix 1.1.1.1/32.

Rack2sw1# show ip bgp neighbor 192.168.13.3 advertised-routes
  Status codes: * - valid, > - best, i - internal, e - external, s - stale
  Origin codes: i - IGP, e - EGP, ? - incomplete

     Network            Nexthop         Metric     LocalPref  Weight AsPath
     ------------------ --------------- ---------- ---------- ------ ---------
*>e  1.1.1.1/32         192.168.13.1    0          0          32768  12       ?


Rack2sw2# show ip bgp neighbor 192.168.23.3 advertised-routes
  Status codes: * - valid, > - best, i - internal, e - external, s - stale
  Origin codes: i - IGP, e - EGP, ? - incomplete

     Network            Nexthop         Metric     LocalPref  Weight AsPath
     ------------------ --------------- ---------- ---------- ------ ---------
*>e  1.1.1.1/32         192.168.23.2    0          0          0      12       ?

 

The BGP configuration only contains neighbor statements.

Rack2sw1# show running-config router bgp

Running configuration:

router bgp 12
   enable
   redistribute connected
   neighbor 192.168.12.2 remote-as 12
   neighbor 192.168.13.3 remote-as 1

Rack2sw2# show running-config router bgp

Running configuration:

router bgp 12
   enable
   neighbor 192.168.12.1 remote-as 12
   neighbor 192.168.23.3 remote-as 13

 

The current BGP implementation supports the following route selection sequence:

Prefer the route with the lowest Administrative Distance.

Prefer the route with the larger weight.

Prefer the route with the highest LOCAL_PREF value.

Prefer the path that was locally originated via a network or through redistribution from an IGP.



Configuration:

The modified BGP configuration contains an out-going route-map statement. The Route-Map checks for the IP address defined in the IP-Prefix “Loopback-0” and if a match occurs, the origin value is set to igp.

Rack2sw2# show running-config router bgp

Running configuration:

router bgp 12
   enable
   neighbor 192.168.12.1 remote-as 12
   neighbor 192.168.23.3 remote-as 13
   neighbor 192.168.23.3 route-map "set-origin" out

Rack2sw2# show ip prefix-list

 ip prefix-list Loopback-0: 1 entries
    5            permit 1.1.1.1/32 ge 32 le 32

route-map "set-origin" permit seq 10
   match ip address prefix-list "Loopback-0"
   set origin igp



Verification

Rack2sw2# show ip bgp neighbor 192.168.23.3 advertised-routes

  Status codes: * - valid, > - best, i - internal, e - external, s - stale
  Origin codes: i - IGP, e - EGP, ? - incomplete

     Network            Nexthop         Metric     LocalPref  Weight AsPath
     ------------------ --------------- ---------- ---------- ------ ---------
*>e  1.1.1.1/32         192.168.23.2    0          0          0      12       i


Rack2sw3# show ip route bgp 1.1.1.1

                          IP Route Entries to 1.1.1.1

  Destination        Gateway         VLAN Type      Sub-Type   Metric     Dist.
  ------------------ --------------- ---- --------- ---------- ---------- -----
  1.1.1.1/32         192.168.23.2    23   bgp       external   0          170


Rack2sw3# show ip bgp 1.1.1.1/255.255.255.255

  Local AS            : 13            Local Router-id  : 192.168.13.3
  BGP Table Version   : 136

  Network     : 1.1.1.1/32            Nexthop          : 192.168.13.1
  Peer        : 192.168.13.1          Origin           : incomplete
  Metric      : 0                            Local Pref       :
  Weight      : 0                           Calc. Local Pref : 100
  Valid       : Yes                          Type             : external
  Stale       : No
  Best        : No
  AS-Path     : 12
  Communities :

  Network     : 1.1.1.1/32            Nexthop          : 192.168.23.2
  Peer        : 192.168.23.2          Origin           : igp
  Metric      : 0                             Local Pref       :
  Weight      : 0                            Calc. Local Pref : 100
  Valid       : Yes                           Type             : external
  Stale       : No
  Best        : Yes (More Reliable Origin)
  AS-Path     : 12
  Communities :

 

Rack2sw2# debug ip bgp packet update


0000:03:44:24.11 BGP  eRouteCtrl:BGP SEND 192.168.23.2+179 -> 192.168.23.3+58542
0000:03:44:24.19 BGP  eRouteCtrl:BGP SEND message type 2 (Update) length 46
0000:03:44:24.27 BGP  eRouteCtrl:BGP SEND flags 0x40 code Origin(1): IGP <=====*****=====
0000:03:44:24.35 BGP  eRouteCtrl:BGP SEND flags 0x40 code ASPath(2) length 4: 12
0000:03:44:24.43 BGP  eRouteCtrl:BGP SEND flags 0x40 code NextHop(3):   192.168.23.2
0000:03:44:24.53 BGP  eRouteCtrl:BGP SEND       1.1.1.1/32
 


 

Version history
Revision #:
1 of 1
Last update:
‎03-30-2020 10:34 AM
Updated by:
 
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