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BGP question on same AS for two locations

 

 

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QChen at corp

May 15, 2011, 8:33 AM

Post #1 of 4 (1722 views)
Permalink
BGP question on same AS for two locations

Hi all,

I have a question: Can we use the same AS number for two different
locations but not IGP routable? The goal is for DR purpose so that the
two sites can communicate.

The situation can happen when the internal connections between two sites
lose at the same time.

Site A: prefix 10.1.1.0/24 advertised to providers with AS number 11111
Site B: prefix 10.1.2.0/24 advertised to peroviders with AS number 11111

No internal connections between A & B (so no IGP between A&B), we want
communication between 10.1.1.0/24 and 10.1.2.0/24.


Thanks

-Qinxue


routehero at gmail

May 15, 2011, 8:44 AM

Post #2 of 4 (1658 views)
Permalink
Re: BGP question on same AS for two locations [In reply to]

Use a static route to one or all upstream.

Inelegant but it works.
On 2011 5 15 11:35, "Chen, Qinxue" <QChen [at] corp> wrote:
> Hi all,
>
> I have a question: Can we use the same AS number for two different
> locations but not IGP routable? The goal is for DR purpose so that the
> two sites can communicate.
>
> The situation can happen when the internal connections between two sites
> lose at the same time.
>
> Site A: prefix 10.1.1.0/24 advertised to providers with AS number 11111
> Site B: prefix 10.1.2.0/24 advertised to peroviders with AS number 11111
>
> No internal connections between A & B (so no IGP between A&B), we want
> communication between 10.1.1.0/24 and 10.1.2.0/24.
>
>
> Thanks
>
> -Qinxue


nsp at rhanssen

May 15, 2011, 8:50 AM

Post #3 of 4 (1661 views)
Permalink
Re: BGP question on same AS for two locations [In reply to]

Hello Qinxue,

actually you can do that (we have such a setup running for nearly 10 yeras
now).
You need to take care of 2 things:
- the upstream sessions must have allowas-in configured
- your upstream provider that connects your locations needs to send you
routes with your AS in path. In our case he stopped doing that after
moving from Cisco to Juniper one day (told us it is a different default
behaviour) which resulted in an outage.

regards
Rolf

> Hi all,
>
> I have a question: Can we use the same AS number for two different
> locations but not IGP routable? The goal is for DR purpose so that the
> two sites can communicate.
>
> The situation can happen when the internal connections between two sites
> lose at the same time.
>
> Site A: prefix 10.1.1.0/24 advertised to providers with AS number 11111
> Site B: prefix 10.1.2.0/24 advertised to peroviders with AS number 11111
>
> No internal connections between A & B (so no IGP between A&B), we want
> communication between 10.1.1.0/24 and 10.1.2.0/24.
>
>
> Thanks
>
> -Qinxue


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http://puck.nether.net/mailman/listinfo/foundry-nsp


QChen at corp

May 15, 2011, 9:01 AM

Post #4 of 4 (1661 views)
Permalink
Re: BGP question on same AS for two locations [In reply to]

Great! Thank you Rolf.

-----Original Message-----
From: "Rolf Han▀en" [mailto:nsp [at] rhanssen]
Sent: Sunday, May 15, 2011 8:51 AM
To: Chen, Qinxue
Cc: foundry-nsp [at] puck
Subject: Re: [f-nsp] BGP question on same AS for two locations

Hello Qinxue,

actually you can do that (we have such a setup running for nearly 10 yeras now).
You need to take care of 2 things:
- the upstream sessions must have allowas-in configured
- your upstream provider that connects your locations needs to send you routes with your AS in path. In our case he stopped doing that after moving from Cisco to Juniper one day (told us it is a different default
behaviour) which resulted in an outage.

regards
Rolf

> Hi all,
>
> I have a question: Can we use the same AS number for two different
> locations but not IGP routable? The goal is for DR purpose so that the
> two sites can communicate.
>
> The situation can happen when the internal connections between two
> sites lose at the same time.
>
> Site A: prefix 10.1.1.0/24 advertised to providers with AS number
> 11111 Site B: prefix 10.1.2.0/24 advertised to peroviders with AS
> number 11111
>
> No internal connections between A & B (so no IGP between A&B), we want
> communication between 10.1.1.0/24 and 10.1.2.0/24.
>
>
> Thanks
>
> -Qinxue



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