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Priorize Default Route fr...

Priorize Default Route from Specific PE

Created: Jun 15, 2021 15:31:50Latest reply: Jun 22, 2021 12:20:45 438 7 2 0 0
  Rewarded HiCoins： 5 (problem resolved)
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Hi,


Is it possible to prioritize one of many default routes received in a PE?


default route


In this example, PE 40 has received default route from 3 other PE (that receive default route from upstream providers)


If it chose PE 30 default route how can I prioritize the default route received from PE 20 on it ?


In my scenario each PE peered to upstream providers receive default route and tag them with a specific community


e.g.: default route received on PE 20 from upstream provider (AS 300) gets 65000:20 community before be sent to other PE to be used as a criteria for selection on iBGP peers.


#


I've tried something like this on PE 40, but they didn't work:


Preference:


#
ip community-filter basic DEFAULT-ROUTE-PE20 permit 65000:20
#
route-policy IBGP-IN permit node 40
 if-match community-filter DEFAULT-ROUTE-PE20
 apply preference 254
#
route-policy IBGP-IN permit node 50
#



Prefval (Weight)


#
ip community-filter basic DEFAULT-ROUTE-PE20 permit 65000:20
#
route-policy IBGP-IN permit node 40
 if-match community-filter DEFAULT-ROUTE-PE20
 apply preferred-value 10
#
route-policy IBGP-IN permit node 50
#



Thanks!

bgpdefault routepeS6730-H

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(0) (0)
Popeye_Wang
Admin Created Jun 16, 2021 07:16:34

Hi,

a.You can run the display bgp routing-table community command to check whether the received default route carries community.

b. Where did you apply the route policy?

c. Is a default route preferred or three routes work in load balancing mode now? You can run the display bgp routing-table 0.0.0.0 command to check the route selection. By default, BGP routes do not work in load balancing mode. You can view the reason why a BGP route is not preferentially selected.


Example.


<R1>dis bgp routing-table 0.0.0.0


BGP local router ID : 20.1.1.1

Local AS number : 200

Paths:   2 available, 1 best, 1 select

BGP routing table entry information of 0.0.0.0/0:

From: 20.1.1.2 (20.1.1.2)

Route Duration: 00h06m10s 

Relay IP Nexthop: 0.0.0.0

Relay IP Out-Interface: GigabitEthernet0/0/0

Original nexthop: 20.1.1.2

Qos information : 0x0

AS-path Nil, origin incomplete, MED 0, localpref 100, pref-val 0, valid, interna

l, best, select, active, pre 200

Not advertised to any peer yet


BGP routing table entry information of 0.0.0.0/0:

From: 30.1.1.2 (30.1.1.2)

Route Duration: 00h00m17s 

Direct Out-interface: GigabitEthernet0/0/2

Original nexthop: 30.1.1.2

Qos information : 0x0

AS-path 100, origin igp, MED 0, pref-val 0, valid, external, pre 20, not preferr

ed for AS-Path

Not advertised to any peer yet


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ptomasi
ptomasi Created Jun 16, 2021 15:23:50 (0) (0)
Hi,

All customization are being made on PE 40

Command display bgp routing-table community shows only one default route active (the default route coming from PE 30 = AS 400 = community 65000:30)

I would like to prioritize default route coming from PE 20 = AS 300 = community 65000:20 using some resource as Preference or Preference-Value (Weight) to influence decision only on this PE

Default route from PE 20 is not elected as the best because of IGP cost:
> not preferred for IGP cos 
All Answers
(0) (0)
2#
Gustavo.HdezF
Gustavo.HdezF Admin Created Jun 15, 2021 15:54:13

Hello User. we are reviewing your question and we will answer you shortly. Thanks.
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(0) (0)
3#
EL.BODO
EL.BODO Created Jun 15, 2021 16:44:28

i think that is possible. The router can copared the next-hope ip address Priorize Default Route from Specific PE-3972799-1
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4#
andersoncf1
andersoncf1 MVE Author Created Jun 15, 2021 18:09:54

Good question
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(0) (0)
5#
Popeye_Wang
Popeye_Wang Admin Created Jun 16, 2021 07:16:34

Hi,

a.You can run the display bgp routing-table community command to check whether the received default route carries community.

b. Where did you apply the route policy?

c. Is a default route preferred or three routes work in load balancing mode now? You can run the display bgp routing-table 0.0.0.0 command to check the route selection. By default, BGP routes do not work in load balancing mode. You can view the reason why a BGP route is not preferentially selected.


Example.


<R1>dis bgp routing-table 0.0.0.0


BGP local router ID : 20.1.1.1

Local AS number : 200

Paths:   2 available, 1 best, 1 select

BGP routing table entry information of 0.0.0.0/0:

From: 20.1.1.2 (20.1.1.2)

Route Duration: 00h06m10s 

Relay IP Nexthop: 0.0.0.0

Relay IP Out-Interface: GigabitEthernet0/0/0

Original nexthop: 20.1.1.2

Qos information : 0x0

AS-path Nil, origin incomplete, MED 0, localpref 100, pref-val 0, valid, interna

l, best, select, active, pre 200

Not advertised to any peer yet


BGP routing table entry information of 0.0.0.0/0:

From: 30.1.1.2 (30.1.1.2)

Route Duration: 00h00m17s 

Direct Out-interface: GigabitEthernet0/0/2

Original nexthop: 30.1.1.2

Qos information : 0x0

AS-path 100, origin igp, MED 0, pref-val 0, valid, external, pre 20, not preferr

ed for AS-Path

Not advertised to any peer yet


View more
  • x
  • convention：

ptomasi
ptomasi Created Jun 16, 2021 15:23:50 (0) (0)
Hi,

All customization are being made on PE 40

Command display bgp routing-table community shows only one default route active (the default route coming from PE 30 = AS 400 = community 65000:30)

I would like to prioritize default route coming from PE 20 = AS 300 = community 65000:20 using some resource as Preference or Preference-Value (Weight) to influence decision only on this PE

Default route from PE 20 is not elected as the best because of IGP cost:
> not preferred for IGP cos 
(0) (0)
6#
carter12
carter12 Created Jun 18, 2021 06:45:15

It looks like your routing policy didn't work, where did you apply it? You can run the display routing policy command to check whether there are matching counts.

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(0) (0)
7#
ptomasi
ptomasi Created Jun 22, 2021 12:20:45

Hi,

I applied the route-policy only on PE 40.

I want to manipulate default route election only on this PE. (Prefval/Weight would suit perfectly)

I don't want this manipulation to influence other PEs in AS (as local-preference parameter does)

#

I'll check about matching counts to get some hints about the route-policy behavior, thanks!
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