Cisco XR / Install all BGP routes in FIB

Channels · ‎01-19-2020

Hello,
We have an ASR9006 in the heart of the network which supports 4 eBGP links to 4 different transits with each a fullview.
Our 4 transits are very substantially identical at the AS-Path level of the routes, and therefore, in upload, only the last forwarder settles in the FIB (about 95% of the routes).
Is it possible to force BGP to install all routes of the RIB into the FIB in order to have loadbalancing?
Even better, to install all the roads having a localpref greater than 90?
I use the option "router bgp address-family ipv4 unicast maximum-paths ebgp 2" but this only applies to eBGP having the same AS.
An idea ?

Many thanks

paul driver · ‎01-19-2020

Hello

LB is possible be it in ebgp/ibgp peering

Can you elaborate on you current topology or maybe supply a diagram of your network?

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Paul

Channels · ‎01-19-2020

Hmm ok.

LAN => AS X => AS1
            => AS1
            => AS2
            => AS3

Import: Import all routes from all AS (~800k per BGP Peer (AS1+1+2+3))

Export: Export my route to all AS (1+2+3)

Do you want more details?

paul driver · ‎01-19-2020

Hello

Post a topology digaram please as it not clear n the currnet topology regards the ASR bgp peering.

Is the ASR just a single/mutiple router with 4 ebgp/ibgp peerings?

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Kind Regards
Paul

Channels · ‎01-20-2020

My config is very simple :

ASR support 4 eBGP Link only, two to same AS1 (on two different routers), one to AS2 and one to AS3.

Today, when I take the routes from AS1, I can see the two routes in my FIB because I have the BGP option maximum-paths:

RP/0/RSP0/CPU0:core1#show ip route
B 1.0.0.0/24 [20/0] via AS1.x.x.141, 10:07:25
             [20/0] via AS1.x.x.221, 10:07:25

Now, I also want to put the routes of AS2 and AS3 in my FIB to have even more loadbalancing:

RP/0/RSP0/CPU0:core1#show bgp ipv4 un 1.0.0.0/24 brief 
Network Next Hop Metric LocPrf Weight Path
*    1.0.0.0/24     AS3.y.y.213  100 10  AS3 a 13335 i
*>                  AS1.x.x.141  100 10  AS1 a 13335 i
*                   AS1.x.x.221  100 10  AS1 a 13335 i
*                   AS2.z.z.9    100 10  AS1 a 13335 i

I would like all the RIB routes to be pushed into the FIB, like this (it's a example):

B 1.0.0.0/24 [20/0] via AS1.x.x.141, 10:07:25
             [20/0] via AS1.x.x.221, 10:07:25
             [20/0] via AS2
             [20/0] via AS3

paul driver · ‎01-20-2020

Hello

You can use the weight path attribute on your single bgp router and append a value to each isp peer link with preference given to link with the higher weight

Lastly append you max prefix to allow these extra prefixes

Please rate and mark as an accepted solution if you have found any of the information provided useful.
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Kind Regards
Paul

Channels · ‎01-20-2020

I'm not sure I understand correctly.
I already have a weight of 10 and a local-pref of 100 on all of my route-policies.
Even pushing maximum-paths ebgp 3 , it's the best routes of AS1 that installs and not AS2 and AS3 ?

Conversely, is it possible to tell BGP to ignore the route comparison by AS-Path?

The best solution is to put 4 default route and do not incoming route by BGP?

Like this :

route-policy AS1-IN
    set weight 10
    set local-preference 100
    pass
end-policy
!
route-policy AS2-IN
    set weight 10
    set local-preference 100
    pass
end-policy
!
route-policy AS3-IN
    set weight 10
    set local-preference 100
    pass
end-policy
!

router bgp
 address-family ipv4 unicast
  maximum-paths ebgp 3
!

paul driver · ‎01-20-2020

Hello

@Channels wrote:

I'm not sure I understand correctly.
I already have a weight of 10 and a local-pref of 100 on all of my route-policies.

Apologies I may be mis understanding you if the below assumption is incorrect lease explain.
I assume by having multiple prefixes to the same destination you mean populating the bgp rib not the global routing table

Only the best route is entered into the global route table unless the paths are equal then you would have multiple entries

In this topology local preference wont work on a single router, However weight PA will

Setting the same weight value on all links wont provide you any path preference, they need to be different

@Channels wrote:

Conversely, is it possible to tell BGP to ignore the route comparison by AS-Path?

Weight PA take precedence over AS-path

Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Channels · ‎01-20-2020

"Only the best route is entered into the global route table unless the paths are equal then you would have multiple entries"
Obviously, not in my case, it's weird.
I have removed localpref and set weight.
A real example :

Network Next Hop Metric LocPrf Weight Path
* 1.0.0.0/24 134.90.140.x 100 198330 13335 i
* 134.90.140.y 100 198330 13335 i
*> 192.168.98.9 100 43142 13335 i

RP/0/RSP0/CPU0:core1#show ip bgp 1.0.0.0/24
Path #1: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1)
134.90.140.x from 134.90.140.x (134.90.140.x)
Origin IGP, localpref 100, weight 100, valid, external, group-best
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:100
Origin-AS validity: valid
Path #2: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1), (received-only)
134.90.140.x from 134.90.140.x (134.90.140.x)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:100
Origin-AS validity: valid
Path #3: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1)
134.90.140.y from 134.90.140.y (134.90.140.y)
Origin IGP, localpref 100, weight 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:110
Origin-AS validity: valid
Path #4: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1), (received-only)
134.90.140.y from 134.90.140.y (134.90.140.y)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:110
Origin-AS validity: valid
Path #5: Received by speaker 0
Not advertised to any peer
43142 13335, (aggregated by 13335 141.101.67.1)
192.168.98.9 from 192.168.98.9 (10.0.1.2)
Origin IGP, localpref 100, weight 100, valid, external, best, group-best
Received Path ID 0, Local Path ID 1, version 114655870
Community: 13335:10019 13335:19020 13335:20050 13335:20500 13335:20530
Origin-AS validity: valid
Path #6: Received by speaker 0
Not advertised to any peer
43142 13335, (aggregated by 13335 141.101.67.1), (received-only)
192.168.98.9 from 192.168.98.9 (10.0.1.2)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 13335:10019 13335:19020 13335:20050 13335:20500 13335:20530
Origin-AS validity: valid

I have :
RP/0/RSP0/CPU0:core1#show ip route
B 1.0.0.0/24 [20/0] via 192.168.98.9, 00:00:09

I want :

RP/0/RSP0/CPU0:core1#show ip route
B 1.0.0.0/24 [20/0] via 192.168.98.9, 00:00:09

via 134.90.140.x

via 134.90.140.y

paul driver · ‎01-20-2020

Hello

@Channels wrote:
"Only the best route is entered into the global route table unless the paths are equal then you would have multiple entries"
Obviously, not in my case, it's weird.
I have removed localpref and set weight.
A real example :

Network Next Hop Metric LocPrf Weight Path
* 1.0.0.0/24 134.90.140.x 100 198330 13335 i
* 134.90.140.y 100 198330 13335 i
*> 192.168.98.9 100 43142 13335 i

RP/0/RSP0/CPU0:core1#show ip bgp 1.0.0.0/24 <----------------------Local bgp adj-rib In
Path #1: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1)
134.90.140.x from 134.90.140.x (134.90.140.x)
Origin IGP, localpref 100, weight 100, valid, external, group-best
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:100
Origin-AS validity: valid
Path #2: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1), (received-only)
134.90.140.x from 134.90.140.x (134.90.140.x)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:100
Origin-AS validity: valid
Path #3: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1)
134.90.140.y from 134.90.140.y (134.90.140.y)
Origin IGP, localpref 100, weight 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:110
Origin-AS validity: valid
Path #4: Received by speaker 0
Not advertised to any peer
198330 13335, (aggregated by 13335 141.101.67.1), (received-only)
134.90.140.y from 134.90.140.y (134.90.140.y)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 65000:110
Origin-AS validity: valid
Path #5: Received by speaker 0
Not advertised to any peer
43142 13335, (aggregated by 13335 141.101.67.1)
192.168.98.9 from 192.168.98.9 (10.0.1.2)
Origin IGP, localpref 100, weight 100, valid, external, best, group-best
Received Path ID 0, Local Path ID 1, version 114655870
Community: 13335:10019 13335:19020 13335:20050 13335:20500 13335:20530
Origin-AS validity: valid
Path #6: Received by speaker 0
Not advertised to any peer
43142 13335, (aggregated by 13335 141.101.67.1), (received-only)
192.168.98.9 from 192.168.98.9 (10.0.1.2)
Origin IGP, localpref 100, valid, external
Received Path ID 0, Local Path ID 0, version 0
Community: 13335:10019 13335:19020 13335:20050 13335:20500 13335:20530
Origin-AS validity: valid

RP/0/RSP0/CPU0:core1#show ip route <----------------Local rtr route table
B 1.0.0.0/24 [20/0] via 192.168.98.9, 00:00:09

As i said the bgp table has multiple entries - sh ip bgp
And the route table which the router actually users for routing has a single entry - sh ip route

So please confirm do you wish to have multipe route table entries?

Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Channels · ‎01-20-2020

Yes so it is not possible to put all Local bgp adj-rib into local rtr route table unless it comes from the same AS?

paul driver · ‎01-20-2020

Hello

@Channels wrote:

Yes so it is not possible to put all Local bgp adj-rib into local rtr route table unless it comes from the same AS?

No exactly correct you could i guess manipulate various bgp PAs but the end result is that the prefixes need to be equal with the bgp selection process to have multiple entries to the same prefix destination in the route table

Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

Channels · ‎01-20-2020

Do you have an example of how to do this?
We don't really have the same path since the first AS changes.