Re: Slightly OT: PfARGHHHHHHHH!

That is exactly what I was looking for! Much appreciated.

Regards,

Marc

On Mon, Aug 20, 2012 at 5:17 PM, Joe Sanchez <marco207p_at_gmail.com> wrote:

> Marc, does this help:
>
>
> - BGP Autonomous System Number Community Prepend
>
> When an entrance link goes out-of-policy (OOP) due to delay, or in
> images prior to Cisco IOS Releases 15.2(1)T1 and 15.1(2)S, and PfR selects
> a best entrance for an inside prefix, a BGP prepend community is attached
> one at a time (up to a maximum of six) to the inside prefix BGP
> advertisement from the network to another autonomous system such as an ISP. In
> Cisco IOS Releases 15.2(1)T1, 15.1(2)S, and later releases, when an
> entrance link goes out-of-policy (OOP) due to unreachable or loss reasons,
> and PfR selects a best entrance for an inside prefix, six BGP prepend
> communities are attached to the inside prefix BGP advertisement. The BGP
> prepend community will increase the number of autonomous system hops in the
> advertisement of the inside prefix from the ISP to its peers.
> Autonomous system prepend BGP community is the preferred method to be used
> for PfR BGP inbound optimization because there is no risk of the local ISP
> filtering the extra autonomous system hops. There are some issues, for
> example, not all ISPs support the BGP prepend community, ISP policies may
> ignore or modify the autonomous system hops, and a transit ISP may filter
> the autonomous system path. If you use this method of inbound optimization
> and a change is made to an autonomous system, you must issue an outbound
> reconfiguration using the clear ip bgp command.
> The prepend community has to be configured per Border Router and per
> external interfaces because the community value is specific per Service
> Provider.
>
> Configuration Sample:
>
> !
> pfr master
> border 10.4.5.6 key-chain pfr
> interface Ethernet0/1 external
> downgrade bgp community aa:nn (community number in aa:nn format)
> interface Ethernet0/0 internal
> !
>
>
> In this solution guide, PfR will enforce the path by using BGP AS-PATH
> prepend for controlled prefixes. PfR will not try to control an inside
> prefix unless there is an exact match in the BGP routing information base
> (RIB) because PfR does not advertise a new prefix to the Internet.
> Joe Sanchez,
> Chicago, IL
>
> On Mon, Aug 20, 2012 at 6:45 PM, marc edwards <renorider_at_gmail.com> wrote:
>
>> So what is this half baked product my SE sold me? The documentation looks
>> good on Cisco's site and reads
>>
>> To enforce an entrance link selection, PfR offers the following methods:
>> BGP Autonomous System Number Prepend
>>
>> After PfR selects a best entrance for an inside prefix, extra autonomous
>> system hops (up to a maximum of six) are prepended to the inside prefix
>> BGP
>> advertisement over the other entrances. The extra autonomous system hops
>> on
>> the other entrances increase the probability that the best entrance will
>> be
>> used for the inside prefix. This is the default method PfR uses to control
>> an inside prefix, and no user configuration is required.
>> BGP Autonomous System Number Community Prepend
>>
>> After PfR selects a best entrance for an inside prefix, a BGP prepend
>> community is attached to the inside prefix BGP advertisement from the
>> network to another autonomous system such as an ISP. The BGP prepend
>> community will increase the number of autonomous system hops in the
>> advertisement of the inside prefix from the ISP to its peers. Autonomous
>> system prepend BGP community is the preferred method to be used for PfR
>> BGP
>> inbound optimization because there is no risk of the local ISP filtering
>> the extra autonomous system hops. There are some issues, for example, not
>> all ISPs support the BGP prepend community, ISP policies may ignore or
>> modify the autonomous system hops, and a transit ISP may filter the
>> autonomous system path. If you use this method of inbound optimization and
>> a change is made to an autonomous system, you must issue an outbound
>> reconfiguration using the clear ip bgp command.
>>
>>
>>
>> http://www.cisco.com/en/US/docs/ios-xml/ios/pfr/configuration/15-1mt/pfr-bgp-inbound.html#GUID-52E6BAC0-FE00-43DD-BE37-822FC2ED5C0F
>>
>>
>> This sounds great until I read further and find no configuration
>> references
>> to make this happen. Looking through all commands in
>>
>> http://www.cisco.com/en/US/docs/ios-xml/ios/pfr/command/pfr-cr-book.html
>>
>> I don't see anything either.
>>
>>
>> Is this blatant false advertising or am I missing something?
>>
>>
>> Regards,
>>
>> Marc
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Mon Aug 20 2012 - 17:35:04 ART