Re: [Idr] draft-chen-bgp-redist-01.txt

Gyan Mishra <hayabusagsm@gmail.com> Fri, 02 July 2021 00:24 UTC

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From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Thu, 1 Jul 2021 20:23:45 -0400
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To: Robert Raszuk <robert@raszuk.net>
Cc: Enke Chen <enchen@paloaltonetworks.com>, Jenny Yuan <jyuan@paloaltonetworks.com>, "idr@ietf. org" <idr@ietf.org>
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Subject: Re: [Idr] draft-chen-bgp-redist-01.txt
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The main protocols are BGP, OSPF, ISIS, Static

Juniper

https://www.juniper.net/documentation/en_US/junose15.1/topics/task/configuration/ip-route-administrative-distance-configuration.html

Route Source

Default Distance

Connected interface

0

Static route

1

Internal access route

2

Access route

3

External BGP

20

OSPF

110

IS-IS

115

RIP

120

Internal BGP

200

Unknown

255


Cisco

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html


Route SourceDefault Distance Values
Connected interface 0
Static route 1
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5
External Border Gateway Protocol (BGP) 20
Internal EIGRP 90
IGRP 100
OSPF 110
Intermediate System-to-Intermediate System (IS-IS) 115
Routing Information Protocol (RIP) 120
Exterior Gateway Protocol (EGP) 140
On Demand Routing (ODR) 160
External EIGRP 170
Internal BGP 200
Unknown* 255



On Thu, Jul 1, 2021 at 2:54 PM Robert Raszuk <robert@raszuk.net> wrote:

> Gyan,
>
> > My understanding is by default most all implementations that I know of
> for example Cisco & Juniper which have use identical default AD
>
> Can you provide source(s) of your above information ?
>
> To the best of my knowledge they are quite different ...
>
> Cisco:
>
> [image: image.png]
>
> Juniper:
>
> [image: image.png]
>
> Except connected I do not see much of "identical default AD"
>
> And that is as the draft says especially important when your intention is
> to control active - backup paths for a given net.
>
> Thx,
> R.
>
>
> On Thu, Jul 1, 2021 at 8:02 PM Gyan Mishra <hayabusagsm@gmail.com> wrote:
>
>>
>> Hi Enke
>>
>> My understanding is by default most all implementations that I know of
>> for example Cisco & Juniper which have use identical default AD,
>> redistribution of the route only occurs from the source protocol that is
>> being redistributed for example static versus OSPF or ISIS based on AD.
>>
>> So if you have multiple protocols redistribution into BGP, the source
>> protocol with the lowest AD is what is inserted into the default RIB/FIB
>> and its that specific route from the source protocol that is redistributed
>> into BGP.   All implementations that I know of work that way.
>>
>> I don’t see any issue with deterministic redistribution as exists today
>> with implementations.
>>
>> Normally you are only running one IGP but let’s say you are running OSPF
>> and ISIS and you have a Juniper and Cisco ASBR redistribution into BGP, as
>> OSPF has default AD 110, the OSPF prefix would be inserted into the Default
>> RIB and redistributed into BGP.  Let’s say you set AD for ISIS down to 90
>> and now the ISIS route is inserted into the RIB and now both Juniper and
>> Cisco ASBR Will redistribute the ISIS route into BGP.
>>
>> I am not seeing the issue that you are trying to solve.
>>
>> Kind Regards
>>
>> Gyan
>>
>> On Wed, Jun 30, 2021 at 3:19 AM Enke Chen <enchen@paloaltonetworks.com>
>> wrote:
>>
>>> Hi, Robert:
>>>
>>> 1) Usually the default admin-distance is configurable. Having the same
>>> admin-distance across implementations would certainly make things simpler,
>>> but that is not required. What matters is the local_pref value for the
>>> redistribute backup route:
>>>
>>>             local_pref = default_local_pref - delta;
>>>
>>> It needs to be in the right order (relatively) for the "role" the route
>>> is supposed to play.
>>>
>>> It's a good question. We will try to clarify it in the next revision.
>>>
>>> 2) Certainly it would work if we define the "delta" (or "local_pref")
>>> for the redistributed route based on its role (e.g., primary, secondary,
>>> tertiary). But extra config would be needed for specifying the "role".  The
>>> algorithm described in the draft does not require additional config other
>>> than the existing "admin-distance".  When more than two paths are involved
>>> in a multi-vendor environment, the admin-distance needs to be carefully
>>> assigned in order to get the desired local_pref value.
>>>
>>> Thanks.   -- Enke
>>>
>>> On Tue, Jun 29, 2021 at 1:05 PM Robert Raszuk <robert@raszuk.net> wrote:
>>>
>>>> Hi Enke,
>>>>
>>>> How do you assure that admin distance is the same or delta would be the
>>>> same across implementations ?
>>>>
>>>> Looking at say junos I see quite different values then when comparing
>>>> with other implementations ...
>>>>
>>>>
>>>> https://www.juniper.net/documentation/en_US/junos/topics/reference/general/routing-protocols-default-route-preference-values.html
>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.juniper.net_documentation_en-5FUS_junos_topics_reference_general_routing-2Dprotocols-2Ddefault-2Droute-2Dpreference-2Dvalues.html&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=OPLTTSu-451-QhDoSINhI2xYdwiMmfF5A2l8luvN11E&m=iUboWFiSpP9QvSDj9hoG8_DO7R_8EOQvfEHnwyX-mc0&s=GOhXjwEf1z0GAfIQVgVAc4sHvcAog6czTO30VhKwzQk&e=>
>>>>
>>>> Would it be simpler to define here verbatim what the local pref should
>>>> be for redistributed routes ? Then at least those could be used as default
>>>> local pref values unless overwritten by operator's policy during
>>>> redistribution.
>>>>
>>>> Thx,
>>>> Robert
>>>>
>>>>
>>>> On Tue, Jun 29, 2021 at 7:14 PM Enke Chen <enchen@paloaltonetworks.com>
>>>> wrote:
>>>>
>>>>> Hi, Folks:
>>>>>
>>>>> Apologies for the very long delay in updating the draft:
>>>>>
>>>>>        https://datatracker.ietf.org/doc/draft-chen-bgp-redist/01/
>>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__datatracker.ietf.org_doc_draft-2Dchen-2Dbgp-2Dredist_01_&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=OPLTTSu-451-QhDoSINhI2xYdwiMmfF5A2l8luvN11E&m=iUboWFiSpP9QvSDj9hoG8_DO7R_8EOQvfEHnwyX-mc0&s=IBn3kTJmGrWISvSq8L3M9GLLamXIqw7t2PvEdtvhmos&e=>
>>>>>
>>>>> The issue still exists, and shows up from time to time. The revised
>>>>> version provides a complete solution that covers the use cases involving a
>>>>> single router as well as multiple routers in a network.
>>>>>
>>>>> Your review and comments are welcome.
>>>>>
>>>>> Thanks.   -- Enke
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Idr mailing list
>>>>> Idr@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/idr
>>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ietf.org_mailman_listinfo_idr&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=OPLTTSu-451-QhDoSINhI2xYdwiMmfF5A2l8luvN11E&m=iUboWFiSpP9QvSDj9hoG8_DO7R_8EOQvfEHnwyX-mc0&s=O1wpTf7XmDmE4-mQGDJ9YNEx2UVZW-k1meY3fd-tQrE&e=>
>>>>>
>>>> _______________________________________________
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>>>
>> --
>>
>> <http://www.verizon.com/>
>>
>> *Gyan Mishra*
>>
>> *Network Solutions A**rchitect *
>>
>> *Email gyan.s.mishra@verizon.com <gyan.s.mishra@verizon.com>*
>>
>>
>>
>> *M 301 502-1347*
>>
>> --

<http://www.verizon.com/>

*Gyan Mishra*

*Network Solutions A**rchitect *

*Email gyan.s.mishra@verizon.com <gyan.s.mishra@verizon.com>*



*M 301 502-1347*